diff --git a/applications/bulk_upload_finaliser/Dockerfile b/applications/bulk_upload_finaliser/Dockerfile
new file mode 100644
index 00000000..6fa80c48
--- /dev/null
+++ b/applications/bulk_upload_finaliser/Dockerfile
@@ -0,0 +1,35 @@
+FROM public.ecr.aws/lambda/python:3.11
+
+# Postgres host/port/database are baked into the image at build time from the
+# deploy workflow's --build-arg values (GitHub Actions DEV_DB_* secrets),
+# mirroring the landlord_description_overrides Dockerfile. They map onto the
+# POSTGRES_* names PostgresConfig.from_env reads. Username/password are NOT baked
+# in -- Terraform injects those as Lambda env vars from Secrets Manager.
+ARG DEV_DB_HOST
+ARG DEV_DB_PORT
+ARG DEV_DB_NAME
+
+ENV POSTGRES_HOST=${DEV_DB_HOST}
+ENV POSTGRES_PORT=${DEV_DB_PORT}
+ENV POSTGRES_DATABASE=${DEV_DB_NAME}
+
+WORKDIR /var/task
+
+COPY applications/bulk_upload_finaliser/requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+# DDD-shaped packages only -- no pandas, no legacy backend/. The finaliser writes
+# both `property` and the terminal `bulk_address_uploads` status through DDD repos
+# on its own PostgresConfig session (ADR-0013).
+COPY domain/ domain/
+COPY infrastructure/ infrastructure/
+COPY orchestration/ orchestration/
+COPY repositories/ repositories/
+COPY utilities/ utilities/
+COPY applications/ applications/
+
+# Place the handler at the Lambda task root so the runtime resolves
+# ``main.handler`` without an extra package prefix.
+COPY applications/bulk_upload_finaliser/handler.py /var/task/main.py
+
+CMD ["main.handler"]
diff --git a/applications/bulk_upload_finaliser/bulk_upload_finaliser_trigger_body.py b/applications/bulk_upload_finaliser/bulk_upload_finaliser_trigger_body.py
new file mode 100644
index 00000000..086ca291
--- /dev/null
+++ b/applications/bulk_upload_finaliser/bulk_upload_finaliser_trigger_body.py
@@ -0,0 +1,22 @@
+from uuid import UUID
+
+from pydantic import BaseModel, ConfigDict
+
+
+class BulkUploadFinaliserTriggerBody(BaseModel):
+    """Trigger body for the bulk_upload_finaliser Lambda (ADR-0013).
+
+    Dispatched by the Next.js Finalise action via
+    ``POST /v1/bulk-uploads/trigger-finaliser``. ``s3_uri`` is the combiner output
+    (``combined_output_s3_uri``) — the same address/UPRN CSV the old synchronous
+    ``/finalize`` route read.
+    """
+
+    model_config = ConfigDict(extra="allow")
+
+    task_id: UUID
+    sub_task_id: UUID
+    s3_uri: str
+    # bigint in the FE schema; Python int is unbounded so Pydantic stays simple.
+    portfolio_id: int
+    bulk_upload_id: UUID
diff --git a/applications/bulk_upload_finaliser/handler.py b/applications/bulk_upload_finaliser/handler.py
new file mode 100644
index 00000000..72894fa0
--- /dev/null
+++ b/applications/bulk_upload_finaliser/handler.py
@@ -0,0 +1,103 @@
+"""bulk_upload_finaliser Lambda (ADR-0013).
+
+Replaces the synchronous Next.js ``/finalize`` property insert. Thin wiring: parse
+the trigger, read the combiner output CSV from S3, hand the rows to the
+``BulkUploadFinaliserOrchestrator`` (which owns the resolution + persist), then
+write the terminal BulkUpload status directly (ADR-0005 hands terminal ownership to
+the backend). ``complete`` is written in the *same* transaction as the property
+insert (atomic finalise); ``failed`` is written on a fresh session on error.
+
+PostgresConfig-only, like the landlord classifier Lambda — no legacy ``backend/``
+connection — so a single DB config (POSTGRES_*) drives the whole run.
+"""
+
+import logging
+import os
+from typing import Any
+from uuid import UUID
+
+import boto3
+from sqlalchemy.engine import Engine
+
+from applications.bulk_upload_finaliser.bulk_upload_finaliser_trigger_body import (
+    BulkUploadFinaliserTriggerBody,
+)
+from infrastructure.postgres.config import PostgresConfig
+from infrastructure.postgres.engine import commit_scope, make_engine, make_session
+from infrastructure.s3.csv_s3_client import CsvS3Client
+from infrastructure.s3.s3_uri import parse_s3_uri
+from orchestration.bulk_upload_finaliser_orchestrator import (
+    BulkUploadFinaliserOrchestrator,
+)
+from orchestration.task_orchestrator import TaskOrchestrator
+from repositories.bulk_upload.bulk_upload_status_writer_postgres import (
+    BulkUploadStatusWriterPostgresRepository,
+)
+from repositories.property.property_identity_writer_postgres import (
+    PropertyIdentityWriterPostgresRepository,
+)
+from utilities.aws_lambda.subtask_handler import subtask_handler
+
+logger = logging.getLogger(__name__)
+
+
+def _run(engine: Engine, trigger: BulkUploadFinaliserTriggerBody) -> int:
+    bucket, _key = parse_s3_uri(trigger.s3_uri)
+
+    boto3_client: Any = boto3.client  # pyright: ignore[reportUnknownMemberType, reportUnknownVariableType]
+    boto_s3: Any = boto3_client("s3")
+    rows = CsvS3Client(boto_s3, bucket).read_rows(trigger.s3_uri)
+
+    session = make_session(engine)
+    try:
+        orchestrator = BulkUploadFinaliserOrchestrator(
+            property_writer=PropertyIdentityWriterPostgresRepository(session)
+        )
+        status_writer = BulkUploadStatusWriterPostgresRepository(session)
+        # Resolution is pure, so run it before opening the transaction.
+        inserts = orchestrator.to_property_rows(rows, trigger.portfolio_id)
+        # Atomic finalise: insert properties and mark `complete` together — a
+        # failure in either rolls back both, leaving the row for the failure path.
+        with commit_scope(session):
+            inserted = orchestrator.persist(inserts)
+            status_writer.set_status(trigger.task_id, "complete")
+    finally:
+        session.close()
+
+    logger.info(
+        "Finalised bulk upload %s: %d rows read, %d properties inserted.",
+        trigger.bulk_upload_id,
+        len(rows),
+        inserted,
+    )
+    return inserted
+
+
+def _mark_failed(engine: Engine, task_id: UUID) -> None:
+    session = make_session(engine)
+    try:
+        with commit_scope(session):
+            BulkUploadStatusWriterPostgresRepository(session).set_status(
+                task_id, "failed"
+            )
+    finally:
+        session.close()
+
+
+@subtask_handler()
+def handler(
+    body: dict[str, Any], context: Any, task_orchestrator: TaskOrchestrator
+) -> dict[str, int]:
+    trigger = BulkUploadFinaliserTriggerBody.model_validate(body)
+    engine = make_engine(PostgresConfig.from_env(os.environ))
+
+    try:
+        inserted = _run(engine, trigger)
+    except Exception:
+        # Hand the BulkUpload to the terminal `failed` state so the UI leaves
+        # `finalising`; the @subtask_handler also marks the SubTask FAILED on the
+        # re-raise below.
+        _mark_failed(engine, trigger.task_id)
+        raise
+
+    return {"inserted": inserted}
diff --git a/applications/bulk_upload_finaliser/requirements.txt b/applications/bulk_upload_finaliser/requirements.txt
new file mode 100644
index 00000000..6a85a255
--- /dev/null
+++ b/applications/bulk_upload_finaliser/requirements.txt
@@ -0,0 +1,4 @@
+boto3
+pydantic
+sqlmodel
+psycopg2-binary
diff --git a/backend/app/bulk_uploads/router.py b/backend/app/bulk_uploads/router.py
index c050b18c..ea02fd80 100644
--- a/backend/app/bulk_uploads/router.py
+++ b/backend/app/bulk_uploads/router.py
@@ -12,6 +12,7 @@ from backend.app.bulk_uploads.schema import (
     CombinedResultRow,
     CombinedResultsResponse,
     CombinerTriggerRequest,
+    FinaliserTriggerRequest,
     FlagsSummary,
     LandlordOverridesTriggerRequest,
     PostcodeSplitterTriggerRequest,
@@ -113,6 +114,26 @@ async def trigger_landlord_overrides(req: LandlordOverridesTriggerRequest):
     }
 
 
+@router.post("/trigger-finaliser", status_code=202)
+async def trigger_finaliser(req: FinaliserTriggerRequest):
+    settings = get_settings()
+
+    try:
+        sqs = boto3.client("sqs", settings.AWS_DEFAULT_REGION)
+        response = sqs.send_message(
+            QueueUrl=settings.FINALISER_SQS_URL,
+            MessageBody=req.model_dump_json(),
+        )
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"SQS error: {e}")
+
+    return {
+        "task_id": req.task_id,
+        "sub_task_id": req.sub_task_id,
+        "sqs_message_id": response.get("MessageId"),
+    }
+
+
 @router.get("/{task_id}/combined-results", response_model=CombinedResultsResponse)
 async def get_combined_results(
     task_id: UUID,
diff --git a/backend/app/bulk_uploads/schema.py b/backend/app/bulk_uploads/schema.py
index af797cac..759f76ca 100644
--- a/backend/app/bulk_uploads/schema.py
+++ b/backend/app/bulk_uploads/schema.py
@@ -23,6 +23,14 @@ class LandlordOverridesTriggerRequest(BaseModel):
     column_mapping: dict[str, str]
 
 
+class FinaliserTriggerRequest(BaseModel):
+    task_id: str
+    sub_task_id: str
+    s3_uri: str  # combiner output (combined_output_s3_uri)
+    portfolio_id: int
+    bulk_upload_id: str
+
+
 class FlagsSummary(BaseModel):
     duplicates: int
     missing: int
diff --git a/backend/app/config.py b/backend/app/config.py
index f969518d..36fb36a8 100644
--- a/backend/app/config.py
+++ b/backend/app/config.py
@@ -43,6 +43,7 @@ class Settings(BaseSettings):
     POSTCODE_SPLITTER_SQS_URL: str = "changeme"
     COMBINER_SQS_URL: str = "changeme"
     LANDLORD_OVERRIDES_SQS_URL: str = "changeme"
+    FINALISER_SQS_URL: str = "changeme"
 
     # Third parties
     EPC_AUTH_TOKEN: str = "changeme"
diff --git a/backend/ordnanceSurvey/helpers.py b/backend/ordnanceSurvey/helpers.py
index c0d6583b..52fbe9c5 100644
--- a/backend/ordnanceSurvey/helpers.py
+++ b/backend/ordnanceSurvey/helpers.py
@@ -1,4 +1,5 @@
 import urllib.parse
+from typing import Any
 from pydantic import ValidationError
 import requests
 import pandas as pd
@@ -7,13 +8,13 @@ from utils.logger import setup_logger
 logger = setup_logger()
 
 
-def os_places_results_to_dataframe(data: dict) -> pd.DataFrame:
+def os_places_results_to_dataframe(data: dict[str, Any]) -> pd.DataFrame:
     """
     Flatten the OS Places API response results into a DataFrame.
     Each result contains either a DPA or LPI record.
     """
-    results = data.get("results", [])
-    rows = []
+    results: list[dict[str, Any]] = data.get("results", [])
+    rows: list[dict[str, Any]] = []
     for r in results:
         if "DPA" in r:
             rows.append(r["DPA"])
@@ -22,7 +23,7 @@ def os_places_results_to_dataframe(data: dict) -> pd.DataFrame:
     return pd.DataFrame(rows)
 
 
-def lookup_os_places(postcode: str, api_key: str) -> dict:
+def lookup_os_places(postcode: str, api_key: str) -> dict[str, Any]:
     """
     Lookup a postcode using the OS Places API.
     Returns the full API response data or an error dict.
diff --git a/backend/ordnanceSurvey/local_handler/.env.local.example b/backend/ordnanceSurvey/local_handler/.env.local.example
new file mode 100644
index 00000000..b1f0330e
--- /dev/null
+++ b/backend/ordnanceSurvey/local_handler/.env.local.example
@@ -0,0 +1,21 @@
+# Runtime env for the Ordnance Survey handler when run locally via docker compose.
+# Variable names must match backend/app/config.py Settings (DB_*, ORDNANCE_SURVEY_API_KEY)
+# plus the AWS creds boto3 needs for S3 access.
+
+ENVIRONMENT=local
+
+# Database (OS Places postcode cache)
+DB_HOST=
+DB_PORT=5432
+DB_NAME=
+DB_USERNAME=
+DB_PASSWORD=
+
+# Ordnance Survey Places API
+ORDNANCE_SURVEY_API_KEY=
+
+# AWS — read input CSV from / write results to S3
+AWS_ACCESS_KEY_ID=
+AWS_SECRET_ACCESS_KEY=
+AWS_DEFAULT_REGION=eu-west-2
+S3_BUCKET_NAME=retrofit-data-dev
diff --git a/backend/ordnanceSurvey/local_handler/run_local.sh b/backend/ordnanceSurvey/local_handler/run_local.sh
new file mode 100755
index 00000000..345b60ee
--- /dev/null
+++ b/backend/ordnanceSurvey/local_handler/run_local.sh
@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+set -euo pipefail
+cd "$(dirname "$0")"
+
+if [ ! -f .env.local ]; then
+  cp .env.local.example .env.local
+  echo "Created .env.local from the template — fill it in, then re-run." >&2
+  exit 1
+fi
+
+docker compose build --no-cache
+docker compose up --force-recreate
diff --git a/backend/ordnanceSurvey/main.py b/backend/ordnanceSurvey/main.py
index 6e82b468..03020307 100644
--- a/backend/ordnanceSurvey/main.py
+++ b/backend/ordnanceSurvey/main.py
@@ -22,6 +22,7 @@ import uuid
 import os
 
 import pandas as pd
+from tqdm import tqdm
 
 logger: logging.Logger = setup_logger()
 
@@ -152,8 +153,10 @@ def handler(body: dict[str, Any], context: Any, local: bool = False) -> None:
     df["ordnance_survey_lexiscore"] = None
 
     # Process each postcode group at a time
-    for postcode, group in grouped:
-        print(f"Processing postcode: {postcode} ({len(group)} rows)")
+    for postcode, group in tqdm(
+        grouped, total=grouped.ngroups, desc="OS postcodes", unit="postcode"
+    ):
+        tqdm.write(f"Processing postcode: {postcode} ({len(group)} rows)")
         valid_group = AddressMatch.is_valid_postcode(postcode)
         if not valid_group:
             logger.warning(f"Postcode {postcode} is invalid, skipping")
diff --git a/backend/ordnanceSurvey/tests/test_os_match.py b/backend/ordnanceSurvey/tests/test_os_match.py
new file mode 100644
index 00000000..b2d63689
--- /dev/null
+++ b/backend/ordnanceSurvey/tests/test_os_match.py
@@ -0,0 +1,153 @@
+# backend/ordnanceSurvey/tests/test_os_match.py
+"""
+Debug harness for Ordnance Survey address matching.
+
+Mirrors backend/address2UPRN/tests/test_csv.py, but for the OS Places flow:
+for each (User Input, Postcode) case it hits the live OS Places API, scores every
+candidate address with AddressMatch.score (exactly as backend/ordnanceSurvey/main.py
+does), and prints the full ranked breakdown so you can see *why* a match was or
+wasn't found.
+
+Run with -s to see the ranking:
+
+    pytest backend/ordnanceSurvey/tests/test_os_match.py -s
+
+Requires ORDNANCE_SURVEY_API_KEY to be set (config Settings / env); skipped otherwise.
+"""
+
+import csv
+import os
+import time
+from pathlib import Path
+from typing import Any, Optional
+
+import pytest
+
+from backend.ordnanceSurvey.helpers import (
+    lookup_os_places,
+    os_places_results_to_dataframe,
+)
+from backend.utils.addressMatch import AddressMatch
+
+FIXTURE_PATH = Path(__file__).parent / "test_data.csv"
+
+# Be polite to the live OS Places API between cases.
+OS_THROTTLE_SECONDS = 1.0
+
+# Handler treats best_score <= 0 as "no match" (see ordnanceSurvey/main.py).
+MATCH_THRESHOLD = 0.0
+
+
+@pytest.fixture(autouse=True)
+def _throttle_os_requests():
+    yield
+    time.sleep(OS_THROTTLE_SECONDS)
+
+
+def _api_key() -> Optional[str]:
+    # Read straight from the environment so the debug harness doesn't depend on
+    # the full Settings model loading cleanly. Falls back to Settings if unset.
+    key = os.getenv("ORDNANCE_SURVEY_API_KEY")
+    if not key:
+        try:
+            from backend.app.config import get_settings
+
+            key = get_settings().ORDNANCE_SURVEY_API_KEY
+        except Exception:
+            key = None
+    if not key or key == "changeme":
+        return None
+    return key
+
+
+def load_test_cases():
+    with open(FIXTURE_PATH, newline="", encoding="utf-8") as f:
+        reader = csv.DictReader(f)
+        return [
+            pytest.param(
+                row["User Input"],
+                row["Postcode"],
+                (row.get("Expected UPRN") or "").strip(),
+                id=f'{row["User Input"]} [{row["Postcode"]}]',
+            )
+            for row in reader
+        ]
+
+
+def _scored_candidates(
+    user_input: str, postcode: str, api_key: str
+) -> list[dict[str, Any]]:
+    """
+    Fetch OS Places candidates for a postcode (bypassing the DB cache) and score
+    every candidate ADDRESS exactly as ordnanceSurvey/main.py does. Returned
+    ranked best-first.
+    """
+    response: dict[str, Any] = lookup_os_places(postcode, api_key)
+    assert response.get("status") == 200, f"OS Places API failed: {response}"
+    assert "data" in response, f"No data in OS Places response: {response}"
+
+    candidates = os_places_results_to_dataframe(response["data"])
+    records: list[dict[str, Any]] = candidates.to_dict("records")  # type: ignore[assignment]
+
+    scored: list[dict[str, Any]] = []
+    for rec in records:
+        address = str(rec.get("ADDRESS", ""))
+        scored.append(
+            {
+                "uprn": rec.get("UPRN", "?"),
+                "address": address,
+                "normalised": AddressMatch.normalise_address(address),
+                "score": AddressMatch.score(user_input, address),
+            }
+        )
+    scored.sort(key=lambda r: r["score"], reverse=True)
+    return scored
+
+
+def _print_debug(
+    user_input: str, postcode: str, scored: list[dict[str, Any]]
+) -> None:
+    print(f"\n{'=' * 80}")
+    print(f"User input : {user_input!r}")
+    print(f"Normalised : {AddressMatch.normalise_address(user_input)!r}")
+    print(f"Postcode   : {postcode!r}")
+    print(f"Candidates : {len(scored)}")
+    print(f"{'-' * 80}")
+    if not scored:
+        print("(no OS Places candidates returned for this postcode)")
+        return
+    for row in scored[:15]:
+        print(f"  score={row['score']:.4f}  uprn={row['uprn']}")
+        print(f"      ADDRESS    : {row['address']}")
+        print(f"      normalised : {row['normalised']}")
+    print(f"{'=' * 80}")
+
+
+@pytest.mark.integration
+@pytest.mark.parametrize("user_input,postcode,expected_uprn", load_test_cases())
+def test_os_match_finds_candidate(
+    user_input: str,
+    postcode: str,
+    expected_uprn: str,
+):
+    api_key = _api_key()
+    if api_key is None:
+        pytest.skip("ORDNANCE_SURVEY_API_KEY not set")
+
+    scored = _scored_candidates(user_input, postcode, api_key)
+    _print_debug(user_input, postcode, scored)
+
+    best = scored[0] if scored else None
+    best_score = float(best["score"]) if best is not None else 0.0
+
+    # The handler records a match only when best_score > 0. This assertion is
+    # the debug signal: when it fails, the printed ranking above shows why.
+    assert best is not None and best_score > MATCH_THRESHOLD, (
+        f"No OS match for {user_input!r} @ {postcode!r} "
+        f"(best_score={best_score:.4f}). See ranking above."
+    )
+
+    if expected_uprn:
+        assert str(best["uprn"]) == expected_uprn, (
+            f"Best match UPRN {best['uprn']!r} != expected {expected_uprn!r}"
+        )
diff --git a/deployment/terraform/lambda/bulkUploadFinaliser/main.tf b/deployment/terraform/lambda/bulkUploadFinaliser/main.tf
new file mode 100644
index 00000000..0d6685d0
--- /dev/null
+++ b/deployment/terraform/lambda/bulkUploadFinaliser/main.tf
@@ -0,0 +1,49 @@
+data "terraform_remote_state" "shared" {
+  backend = "s3"
+  config = {
+    bucket = "assessment-model-terraform-state"
+    key    = "env:/${var.stage}/terraform.tfstate"
+    region = "eu-west-2"
+  }
+}
+
+data "aws_secretsmanager_secret_version" "db_credentials" {
+  secret_id = "${var.stage}/assessment_model/db_credentials"
+}
+
+locals {
+  db_credentials = jsondecode(data.aws_secretsmanager_secret_version.db_credentials.secret_string)
+}
+
+module "lambda" {
+  source = "../../modules/lambda_with_sqs"
+
+  name  = "bulk-upload-finaliser"
+  stage = var.stage
+
+  image_uri = local.image_uri
+
+  # The finaliser reads the combiner CSV and does one bulk INSERT — IO-light, but
+  # a property list can be ~40,000 rows, so 300s leaves ample headroom under the
+  # queue visibility timeout. batch_size = 1 keeps one upload per invocation so a
+  # bad record can't redrive its siblings; maximum_concurrency caps DB write
+  # fan-out.
+  timeout             = 300
+  batch_size          = 1
+  maximum_concurrency = 2
+
+  environment = merge(
+    {
+      STAGE             = var.stage
+      LOG_LEVEL         = "info"
+      POSTGRES_USERNAME = local.db_credentials.db_assessment_model_username
+      POSTGRES_PASSWORD = local.db_credentials.db_assessment_model_password
+    },
+  )
+}
+
+# Attach S3 read policy so the handler can read the combiner output CSV.
+resource "aws_iam_role_policy_attachment" "bulk_upload_finaliser_s3_read" {
+  role       = module.lambda.role_name
+  policy_arn = data.terraform_remote_state.shared.outputs.bulk_upload_finaliser_s3_read_arn
+}
diff --git a/deployment/terraform/lambda/bulkUploadFinaliser/outputs.tf b/deployment/terraform/lambda/bulkUploadFinaliser/outputs.tf
new file mode 100644
index 00000000..505d902a
--- /dev/null
+++ b/deployment/terraform/lambda/bulkUploadFinaliser/outputs.tf
@@ -0,0 +1,9 @@
+output "bulk_upload_finaliser_queue_url" {
+  value       = module.lambda.queue_url
+  description = "URL of the Bulk Upload Finaliser SQS queue (wire into the FastAPI FINALISER_SQS_URL)"
+}
+
+output "bulk_upload_finaliser_queue_arn" {
+  value       = module.lambda.queue_arn
+  description = "ARN of the Bulk Upload Finaliser SQS queue"
+}
diff --git a/deployment/terraform/lambda/bulkUploadFinaliser/provider.tf b/deployment/terraform/lambda/bulkUploadFinaliser/provider.tf
new file mode 100644
index 00000000..98a588f1
--- /dev/null
+++ b/deployment/terraform/lambda/bulkUploadFinaliser/provider.tf
@@ -0,0 +1,16 @@
+terraform {
+  required_providers {
+    aws = {
+      source  = "hashicorp/aws"
+      version = ">= 5.0"
+    }
+  }
+
+  backend "s3" {
+    bucket = "bulk-upload-finaliser-terraform-state"
+    key    = "terraform.tfstate"
+    region = "eu-west-2"
+  }
+
+  required_version = ">= 1.2.0"
+}
diff --git a/deployment/terraform/lambda/bulkUploadFinaliser/variables.tf b/deployment/terraform/lambda/bulkUploadFinaliser/variables.tf
new file mode 100644
index 00000000..5d45b312
--- /dev/null
+++ b/deployment/terraform/lambda/bulkUploadFinaliser/variables.tf
@@ -0,0 +1,27 @@
+variable "lambda_name" {
+  type        = string
+  description = "Logical name of the lambda (e.g. bulkUploadFinaliser)"
+}
+
+variable "stage" {
+  description = "Deployment stage (e.g. dev, prod)"
+  type        = string
+}
+
+variable "ecr_repo_url" {
+  type        = string
+  description = "ECR repository URL (no tag, no digest)"
+}
+
+variable "image_digest" {
+  type        = string
+  description = "Image digest (sha256:...)"
+}
+
+locals {
+  image_uri = "${var.ecr_repo_url}@${var.image_digest}"
+}
+
+output "resolved_image_uri" {
+  value = local.image_uri
+}
diff --git a/deployment/terraform/lambda/fast-api/main.tf b/deployment/terraform/lambda/fast-api/main.tf
index 3a2b5a5f..dea9b7d9 100644
--- a/deployment/terraform/lambda/fast-api/main.tf
+++ b/deployment/terraform/lambda/fast-api/main.tf
@@ -46,6 +46,15 @@ data "terraform_remote_state" "bulk_address2uprn_combiner" {
   }
 }
 
+data "terraform_remote_state" "bulk_upload_finaliser" {
+  backend = "s3"
+  config = {
+    bucket = "bulk-upload-finaliser-terraform-state",
+    key    = "env:/${var.stage}/terraform.tfstate"
+    region = "eu-west-2"
+  }
+}
+
 ############################################
 # Load Credentials
 ############################################
@@ -105,6 +114,7 @@ module "fastapi" {
     CATEGORISATION_SQS_URL      = data.terraform_remote_state.categorisation.outputs.categorisation_queue_url
     POSTCODE_SPLITTER_SQS_URL   = data.terraform_remote_state.postcode_splitter.outputs.postcode_splitter_queue_url
     COMBINER_SQS_URL            = data.terraform_remote_state.bulk_address2uprn_combiner.outputs.bulk_address2uprn_combiner_queue_url
+    FINALISER_SQS_URL           = data.terraform_remote_state.bulk_upload_finaliser.outputs.bulk_upload_finaliser_queue_url
   }
 }
 
@@ -126,7 +136,8 @@ module "fastapi_sqs_policy" {
     data.terraform_remote_state.engine.outputs.ara_engine_queue_arn,
     data.terraform_remote_state.categorisation.outputs.categorisation_queue_arn,
     data.terraform_remote_state.postcode_splitter.outputs.postcode_splitter_queue_arn,
-    data.terraform_remote_state.bulk_address2uprn_combiner.outputs.bulk_address2uprn_combiner_queue_arn
+    data.terraform_remote_state.bulk_address2uprn_combiner.outputs.bulk_address2uprn_combiner_queue_arn,
+    data.terraform_remote_state.bulk_upload_finaliser.outputs.bulk_upload_finaliser_queue_arn
   ]
 
   conditions = null
diff --git a/deployment/terraform/shared/main.tf b/deployment/terraform/shared/main.tf
index 82a3820a..804082fc 100644
--- a/deployment/terraform/shared/main.tf
+++ b/deployment/terraform/shared/main.tf
@@ -558,6 +558,36 @@ output "bulk_address2uprn_combiner_s3_arn" {
   value = module.bulk_address2uprn_combiner_s3.policy_arn
 }
 
+################################################
+# Bulk Upload Finaliser – Lambda ECR (ADR-0013)
+################################################
+module "bulk_upload_finaliser_state_bucket" {
+  source      = "../modules/tf_state_bucket"
+  bucket_name = "bulk-upload-finaliser-terraform-state"
+}
+
+module "bulk_upload_finaliser_registry" {
+  source = "../modules/container_registry"
+  name   = "bulk_upload_finaliser"
+  stage  = var.stage
+}
+
+# The finaliser only reads the combiner output (bulk_final_outputs) to insert
+# property rows; it writes to Postgres, not S3.
+module "bulk_upload_finaliser_s3_read" {
+  source = "../modules/s3_iam_policy"
+
+  policy_name        = "BulkUploadFinaliserReadS3"
+  policy_description = "Allow bulk_upload_finaliser Lambda to read combiner output from retrofit-data bucket"
+  bucket_arns        = ["arn:aws:s3:::retrofit-data-${var.stage}"]
+  actions            = ["s3:GetObject", "s3:ListBucket"]
+  resource_paths     = ["/bulk_final_outputs/*"]
+}
+
+output "bulk_upload_finaliser_s3_read_arn" {
+  value = module.bulk_upload_finaliser_s3_read.policy_arn
+}
+
 ################################################
 # Categorisation – Lambda ECR
 ################################################
diff --git a/docs/adr/0013-bulk-upload-finaliser-writes-properties.md b/docs/adr/0013-bulk-upload-finaliser-writes-properties.md
new file mode 100644
index 00000000..378351cf
--- /dev/null
+++ b/docs/adr/0013-bulk-upload-finaliser-writes-properties.md
@@ -0,0 +1,120 @@
+# ADR-0013: The `bulk_upload_finaliser` Lambda writes properties and the terminal status
+
+**Status:** Accepted
+**Date:** 2026-06-04
+
+> Companion to the `assessment-model` (frontend) repo's
+> [ADR-0005](https://github.com/Hestia-Homes/assessment-model/blob/main/docs/adr/0005-async-bulk-upload-finaliser.md),
+> which owns the state-machine change and the Drizzle schema. This ADR owns the
+> **backend write path**. It applies the direct-write pattern, transaction-boundary
+> rule, and port/adapter/row-mirror file layout established by
+> [ADR-0003](0003-python-writes-landlord-overrides-directly.md).
+
+## Context
+
+Finalising a BulkUpload inserts one `property` row per source row — up to ~40,000.
+Today a synchronous Next.js route does it; frontend ADR-0005 moves it to a dispatched
+Lambda for the same reasons ADR-0003 moved the classifier write into Python: the work
+is internal (a Lambda computes the rows, the same Lambda persists them), the Lambda
+already sits next to a Postgres connection, and routing 40k inserts back through an
+HTTP hop buys nothing.
+
+`PropertyRow` in this repo
+([`infrastructure/postgres/property_table.py`](../../infrastructure/postgres/property_table.py))
+is currently a **defensive read-only view** — its docstring states the backend never
+inserts properties. Finalise changes that.
+
+## Decision
+
+1. **New application `applications/bulk_upload_finaliser/`** wraps a handler in
+   `@subtask_handler` (auto-injected `TaskOrchestrator`; `run_subtask` owns the
+   subtask start/complete/fail and the Task cascade), exactly like
+   `applications/landlord_description_overrides/handler.py`. The trigger body:
+
+   ```python
+   class BulkUploadFinaliserTriggerBody(SubtaskTriggerBody):  # task_id, sub_task_id
+       s3_uri: str        # combiner output (combined_output_s3_uri)
+       portfolio_id: int
+       bulk_upload_id: UUID
+   ```
+
+   Dispatched via a new `POST /v1/bulk-uploads/trigger-finaliser` FastAPI endpoint
+   (auth `validate_token`) that enqueues to a new SQS queue — mirroring
+   `trigger-postcode-splitter` / `trigger-landlord-overrides`.
+
+2. **`PropertyRow` drops its "backend never inserts" invariant** and gains the
+   insertable columns finalise needs — the **exact nine** the frontend route writes
+   today: `portfolio_id`, `creation_status` (`'READY'`), `uprn`,
+   `landlord_property_id` (← `Internal Reference`), `address` (matched ?? user
+   input), `postcode`, `user_inputted_address`, `user_inputted_postcode`,
+   `lexiscore`. Drizzle remains the schema source of truth (ADR-0003); this is a
+   mirror change only.
+
+3. **Insert policy lives in SQL, idempotent:**
+
+   ```sql
+   INSERT INTO property (portfolio_id, creation_status, uprn, landlord_property_id,
+                         address, postcode, user_inputted_address,
+                         user_inputted_postcode, lexiscore)
+   VALUES …
+   ON CONFLICT (portfolio_id, uprn) WHERE uprn IS NOT NULL
+   DO NOTHING;
+   ```
+
+   This reproduces the frontend's `onConflictDoNothing` exactly — existing properties
+   are not churned on a re-run.
+
+4. **The Lambda writes the terminal BulkUpload status directly — DDD, on its own
+   session.** On success it sets `status='complete'`; on failure `status='failed'`.
+   Rather than the combiner's `backend/app/db/functions` (which open the legacy
+   `backend/` connection on the separate `DB_*` config), the finaliser stays
+   **PostgresConfig-only like the landlord classifier Lambda**: it writes status
+   through a DDD `BulkUploadStatusWriter` port (`repositories/bulk_upload/`) backed
+   by a minimal `BulkAddressUploadRow` mirror (`infrastructure/postgres/`), on the
+   *same* session. So a single DB config (`POSTGRES_*`) drives the run and the
+   image needs no `backend/`. The `complete` flip happens **in the same transaction
+   as the property insert** (atomic finalise — either both land or neither);
+   `failed` is written on a fresh session in the error path. Next.js no longer
+   writes `complete`; it owns only the `awaiting_review → finalising`
+   compare-and-swap at dispatch (frontend ADR-0005).
+
+5. **DDD layering (ADR-0003 + the landlord precedent).** Domain logic — resolving
+   combiner rows into property identity rows — lives in
+   `orchestration/bulk_upload_finaliser_orchestrator.py`; the Lambda
+   `applications/bulk_upload_finaliser/handler.py` stays thin (parse trigger, wire
+   S3 + engine + repos, delegate, report status). New seams:
+   - Property insert: port `repositories/property/property_identity_writer.py`
+     (+ `PropertyIdentityInsert` DTO), adapter
+     `repositories/property/property_identity_writer_postgres.py`, writing the
+     amended `infrastructure/postgres/property_table.py` mirror. A dedicated *writer*
+     distinct from the aggregate-hydrating `PropertyRepository`, which needs an EPC
+     slice the finaliser doesn't.
+   - Status: port `repositories/bulk_upload/bulk_upload_status_writer.py`, adapter
+     `…_postgres.py`, writing the `infrastructure/postgres/bulk_address_upload_table.py`
+     mirror.
+   - Transaction boundary stays in the `infrastructure/postgres/engine` helper
+     (`commit_scope`); the handler opens the context (once, around insert+complete),
+     never calls `.commit()`; orchestrator and repositories never commit.
+
+6. **`property_overrides` is out of scope (v2).** The table exists (frontend
+   migration 0221) but this Lambda does not populate it in v1. When v2 lands it adds
+   a `PropertyOverrideRow` mirror + `infrastructure/property/property_overrides_postgres_repository.py`
+   using `onConflictDoUpdate` per frontend ADR-0005.
+
+## Consequences
+
+**Positive.**
+- 40k inserts run in a Lambda with a single `sub_task` row to observe, not behind a
+  synchronous HTTP request.
+- Reuses the `@subtask_handler` / SQS / direct-Postgres machinery — reviewers have
+  the classifier handler and the combiner status-writers as precedents.
+
+**Negative.**
+- **`PropertyRow` is no longer read-only.** The defensive invariant that made
+  accidental backend property writes impossible is gone; correctness now rests on the
+  finaliser being the only inserting caller.
+- **Terminal-status ownership crosses the repo boundary.** The backend now writes a
+  BulkUpload status (`complete`/`failed`) that Next.js used to own — coordinated only
+  through the status column (frontend ADR-0005's "two writers, extended").
+- The Drizzle/SQLModel lockstep risk from ADR-0003 now extends to `property`'s
+  insertable columns.
diff --git a/infrastructure/postgres/bulk_address_upload_table.py b/infrastructure/postgres/bulk_address_upload_table.py
new file mode 100644
index 00000000..e43d7e84
--- /dev/null
+++ b/infrastructure/postgres/bulk_address_upload_table.py
@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import ClassVar, Optional
+from uuid import UUID
+
+from sqlmodel import Field, SQLModel
+
+
+class BulkAddressUploadRow(SQLModel, table=True):
+    """Minimal mirror of the FE-owned ``bulk_address_uploads`` table.
+
+    The schema source of truth is the Next.js Drizzle repo
+    (``src/app/db/schema/bulk_address_uploads.ts``); the backend's fuller mirror
+    lives at ``backend/app/db/models/bulk_address_uploads.py``. This DDD-side
+    mirror declares only the columns the finaliser writes — the terminal status —
+    so the finaliser can flip status on its own ``PostgresConfig`` session without
+    pulling in the legacy ``backend/`` connection (ADR-0013). Keep the column names
+    in step with the Drizzle source.
+    """
+
+    __tablename__: ClassVar[str] = "bulk_address_uploads"  # pyright: ignore[reportIncompatibleVariableOverride]
+
+    id: UUID = Field(primary_key=True)
+    task_id: Optional[UUID] = Field(default=None, index=True)
+    status: str
+    updated_at: datetime = Field(
+        default_factory=lambda: datetime.now(timezone.utc)
+    )
diff --git a/infrastructure/postgres/property_table.py b/infrastructure/postgres/property_table.py
index 6bd2d644..c333cad4 100644
--- a/infrastructure/postgres/property_table.py
+++ b/infrastructure/postgres/property_table.py
@@ -2,24 +2,49 @@ from __future__ import annotations
 
 from typing import ClassVar, Optional
 
+from sqlalchemy import Column
+from sqlalchemy import Enum as SAEnum
 from sqlmodel import Field, SQLModel
 
+# Mirror of the FE-owned `creation_status` pgEnum (property.ts:
+# propertyCreationStatusEnum = {LOADING, READY, ERROR}). A single SAEnum instance
+# so test-schema create_all emits one CREATE TYPE; prod owns the type via Drizzle.
+property_creation_status_sa_enum = SAEnum(
+    "LOADING", "READY", "ERROR", name="creation_status"
+)
+
 
 class PropertyRow(SQLModel, table=True):
-    """Defensive view of the FE-owned ``property`` table.
+    """Mirror of the FE-owned ``property`` table.
 
-    The schema and migrations for ``property`` are owned by the front-end
-    Next.js repo; this declares only the identity columns the modelling backend
-    reads/writes, so FE-owned migrations to other columns don't ripple into us.
+    The schema and migrations for ``property`` are owned by the front-end Next.js
+    repo (``src/app/db/schema/property.ts``); this declares the identity columns
+    the modelling backend reads, plus the subset the ``bulk_upload_finaliser``
+    Lambda **inserts** at Finalise (ADR-0013). It is no longer read-only — the
+    finaliser is the one backend caller that inserts. Columns not declared here
+    are still owned by FE migrations and don't ripple into us.
     """
 
     __tablename__: ClassVar[str] = "property"  # pyright: ignore[reportIncompatibleVariableOverride]
 
-    # Non-Optional: this is a read-only defensive view of the FE-owned ``property``
-    # table — the backend never inserts rows, so every row read carries an id.
-    id: int = Field(primary_key=True)
+    # bigserial in the FE schema — DB-assigned on insert, so Optional/None on the
+    # way in and always populated on the way out.
+    id: Optional[int] = Field(default=None, primary_key=True)
     portfolio_id: int
-    postcode: str
-    address: str
+    # Nullable in the FE schema. The finaliser writes `matched ?? user-inputted`,
+    # which is absent for fully-unmatched rows.
+    postcode: Optional[str] = Field(default=None)
+    address: Optional[str] = Field(default=None)
     uprn: Optional[int] = Field(default=None)
     landlord_property_id: Optional[str] = Field(default=None)
+
+    # Insertable columns the finaliser writes (ADR-0013). All nullable in the FE
+    # schema except `creation_status` (NOT NULL); the finaliser always sets it to
+    # 'READY', so a nullable mirror is safe — the real column enforces NOT NULL.
+    creation_status: Optional[str] = Field(
+        default=None,
+        sa_column=Column(property_creation_status_sa_enum, nullable=True),
+    )
+    user_inputted_address: Optional[str] = Field(default=None)
+    user_inputted_postcode: Optional[str] = Field(default=None)
+    lexiscore: Optional[float] = Field(default=None)
diff --git a/orchestration/bulk_upload_finaliser_orchestrator.py b/orchestration/bulk_upload_finaliser_orchestrator.py
new file mode 100644
index 00000000..44d65178
--- /dev/null
+++ b/orchestration/bulk_upload_finaliser_orchestrator.py
@@ -0,0 +1,125 @@
+"""Finalises a BulkUpload into ``property`` rows (ADR-0013).
+
+The domain logic of Finalise: turn the combiner output rows into property identity
+rows (the same resolution the old Next.js ``/finalize`` route did) and persist them
+through the injected writer. Like every orchestrator it never commits — the caller
+owns the transaction boundary (see the Lambda handler).
+"""
+
+from __future__ import annotations
+
+import re
+from typing import Any, Optional
+
+from repositories.property.property_identity_writer import (
+    PropertyIdentityInsert,
+    PropertyIdentityWriter,
+)
+
+# Combiner-output columns — identical to the old frontend /finalize route and the
+# backend combined-results reader (router.py).
+ADDRESS_COLS = ("Address 1", "Address 2", "Address 3")
+POSTCODE_COL = "postcode"
+INTERNAL_REF_COL = "Internal Reference"
+UPRN_COL = "address2uprn_uprn"
+MATCHED_ADDRESS_COL = "address2uprn_address"
+LEXISCORE_COL = "address2uprn_lexiscore"
+MISSING_SENTINEL = "invalid postcode"
+UK_POSTCODE_RE = re.compile(r"[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}", re.IGNORECASE)
+
+
+def _normalize(value: Any) -> str:
+    if value is None:
+        return ""
+    return str(value).strip()
+
+
+def _is_missing(value: str) -> bool:
+    return value == "" or value.lower() == MISSING_SENTINEL
+
+
+def _parse_uprn(raw: Any) -> Optional[int]:
+    val = _normalize(raw)
+    if _is_missing(val):
+        return None
+    try:
+        return int(val)
+    except ValueError:
+        return None
+
+
+def _parse_lexiscore(raw: Any) -> Optional[float]:
+    val = _normalize(raw)
+    if _is_missing(val):
+        return None
+    try:
+        return float(val)
+    except ValueError:
+        return None
+
+
+def _extract_postcode(matched: Optional[str], fallback: str) -> Optional[str]:
+    if matched:
+        m = UK_POSTCODE_RE.search(matched)
+        if m:
+            return m.group(0).upper()
+    return fallback or None
+
+
+class BulkUploadFinaliserOrchestrator:
+    def __init__(self, property_writer: PropertyIdentityWriter) -> None:
+        self._property_writer = property_writer
+
+    def to_property_rows(
+        self, rows: list[dict[str, str]], portfolio_id: int
+    ) -> list[PropertyIdentityInsert]:
+        """Resolve combiner rows into property identity inserts.
+
+        Pure (no DB / IO), so the caller can run it before opening a transaction.
+        Reproduces the old ``/finalize`` route's resolution exactly: matched
+        address falls back to the user-inputted one; postcode is extracted from
+        the matched address or falls back to the user-inputted postcode.
+        """
+        return [self._row_to_insert(raw, portfolio_id) for raw in rows]
+
+    def persist(self, inserts: list[PropertyIdentityInsert]) -> int:
+        """Insert the resolved rows via the writer (idempotent — see the adapter).
+
+        Does not commit; the caller opens the transaction around this call.
+        Returns the number of properties actually inserted.
+        """
+        return self._property_writer.insert_all(inserts)
+
+    @staticmethod
+    def _row_to_insert(
+        raw: dict[str, str], portfolio_id: int
+    ) -> PropertyIdentityInsert:
+        user_inputted_address = (
+            ", ".join(p for p in (_normalize(raw.get(c)) for c in ADDRESS_COLS) if p)
+            or None
+        )
+        user_inputted_postcode = _normalize(raw.get(POSTCODE_COL)) or None
+
+        uprn = _parse_uprn(raw.get(UPRN_COL))
+
+        matched_address_raw = _normalize(raw.get(MATCHED_ADDRESS_COL))
+        matched_address = (
+            None if _is_missing(matched_address_raw) else matched_address_raw
+        )
+
+        address = matched_address or user_inputted_address
+        postcode = _extract_postcode(matched_address, user_inputted_postcode or "")
+        internal_ref = _normalize(raw.get(INTERNAL_REF_COL)) or None
+        lexiscore = _parse_lexiscore(raw.get(LEXISCORE_COL))
+
+        return PropertyIdentityInsert(
+            portfolio_id=portfolio_id,
+            uprn=uprn,
+            landlord_property_id=internal_ref,
+            address=address,
+            postcode=postcode,
+            user_inputted_address=user_inputted_address,
+            user_inputted_postcode=user_inputted_postcode,
+            lexiscore=lexiscore,
+            creation_status="READY",
+        )
diff --git a/pytest.ini b/pytest.ini
index 47b40c17..1303dcb4 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -7,6 +7,7 @@ testpaths =
     recommendations/tests
     backend/tests
     backend/address2UPRN/tests
+    backend/ordnanceSurvey/tests
     backend/app/db/functions/tests
     backend/categorisation/tests
     backend/condition/tests
@@ -25,7 +26,5 @@ testpaths =
     etl/epc_clean/tests
     etl/hubspot/tests
     etl/spatial/tests
-    domain/sap10_ml/tests
-    tests/
 markers =
     integration: mark a test as an integration test
diff --git a/repositories/bulk_upload/bulk_upload_status_writer.py b/repositories/bulk_upload/bulk_upload_status_writer.py
new file mode 100644
index 00000000..70fdb1b2
--- /dev/null
+++ b/repositories/bulk_upload/bulk_upload_status_writer.py
@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from uuid import UUID
+
+
+class BulkUploadStatusWriter(ABC):
+    """Port: writes the terminal BulkUpload status at Finalise (ADR-0013).
+
+    The finaliser owns the terminal write — Next.js no longer writes ``complete``;
+    it only flips ``awaiting_review → finalising`` at dispatch (ADR-0005). This is
+    the backend half of that "two writers" split, alongside the combiner's
+    ``combining``/``awaiting_review`` writes.
+    """
+
+    @abstractmethod
+    def set_status(self, task_id: UUID, status: str) -> None:
+        """Set the status of the bulk_address_uploads row for ``task_id``.
+
+        Does not commit — the caller owns the transaction boundary, so the status
+        flip can share the same transaction as the property insert (atomic
+        finalise) or run in its own session for the failure path.
+        """
+        ...
diff --git a/repositories/bulk_upload/bulk_upload_status_writer_postgres.py b/repositories/bulk_upload/bulk_upload_status_writer_postgres.py
new file mode 100644
index 00000000..ba83c4d7
--- /dev/null
+++ b/repositories/bulk_upload/bulk_upload_status_writer_postgres.py
@@ -0,0 +1,33 @@
+"""Postgres adapter for ``BulkUploadStatusWriter`` (ADR-0013).
+
+Flips the ``bulk_address_uploads`` status on the caller's session — so the
+finaliser can mark ``complete`` in the *same* transaction as the property insert
+(atomic finalise), and mark ``failed`` in a fresh session on the error path.
+"""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from uuid import UUID
+
+from sqlmodel import Session, select
+
+from infrastructure.postgres.bulk_address_upload_table import BulkAddressUploadRow
+from repositories.bulk_upload.bulk_upload_status_writer import BulkUploadStatusWriter
+
+
+class BulkUploadStatusWriterPostgresRepository(BulkUploadStatusWriter):
+    def __init__(self, session: Session) -> None:
+        self._session = session
+
+    def set_status(self, task_id: UUID, status: str) -> None:
+        row = self._session.exec(
+            select(BulkAddressUploadRow).where(
+                BulkAddressUploadRow.task_id == task_id
+            )
+        ).first()
+        if row is None:
+            raise ValueError(f"No bulk_address_uploads row for task_id {task_id}")
+        row.status = status
+        row.updated_at = datetime.now(timezone.utc)
+        self._session.add(row)
diff --git a/repositories/property/property_identity_writer.py b/repositories/property/property_identity_writer.py
new file mode 100644
index 00000000..a5db0129
--- /dev/null
+++ b/repositories/property/property_identity_writer.py
@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import Optional
+
+
+@dataclass(frozen=True)
+class PropertyIdentityInsert:
+    """One row the finaliser inserts into the FE-owned ``property`` table.
+
+    Mirrors the exact column set today's Next.js ``/finalize`` writes (ADR-0013):
+    nine fields plus ``creation_status='READY'``. ``address``/``postcode`` are the
+    resolved (matched ?? user-inputted) values and may be ``None``.
+    """
+
+    portfolio_id: int
+    uprn: Optional[int]
+    landlord_property_id: Optional[str]
+    address: Optional[str]
+    postcode: Optional[str]
+    user_inputted_address: Optional[str]
+    user_inputted_postcode: Optional[str]
+    lexiscore: Optional[float]
+    creation_status: str = "READY"
+
+
+class PropertyIdentityWriter(ABC):
+    """Port: bulk-inserts ``property`` identity rows at Finalise (ADR-0013).
+
+    Distinct from ``PropertyRepository`` (which hydrates the Property *aggregate*
+    for reads and needs an EPC slice). This writer only persists identity rows and
+    has no read/EPC dependency. Idempotent on re-run: existing properties are not
+    churned — see the adapter's conflict policy.
+    """
+
+    @abstractmethod
+    def insert_all(self, rows: list[PropertyIdentityInsert]) -> int:
+        """Insert all rows, skipping any whose ``(portfolio_id, uprn)`` already
+        exists (the FE partial unique index, ``WHERE uprn IS NOT NULL``). Rows with
+        no UPRN are always inserted. Returns the number of rows actually inserted.
+        An empty list is a no-op returning 0."""
+        ...
diff --git a/repositories/property/property_identity_writer_postgres.py b/repositories/property/property_identity_writer_postgres.py
new file mode 100644
index 00000000..2be9aba5
--- /dev/null
+++ b/repositories/property/property_identity_writer_postgres.py
@@ -0,0 +1,63 @@
+"""Postgres adapter for ``PropertyIdentityWriter`` (ADR-0013).
+
+Bulk-inserts ``property`` identity rows through the ``PropertyRow`` SQLModel
+mirror. The conflict policy lives in SQL and reproduces today's Next.js
+``onConflictDoNothing`` exactly: skip a row whose ``(portfolio_id, uprn)`` already
+exists under the FE partial unique index ``uq_property_portfolio_uprn``
+(``WHERE uprn IS NOT NULL``); rows with no UPRN are always inserted. This makes a
+re-run leave existing properties untouched — contrast ``property_overrides``,
+which recalculates (ADR-0005).
+"""
+
+from __future__ import annotations
+
+from typing import Any, cast
+
+from sqlalchemy import Table
+from sqlalchemy.dialects.postgresql import insert as pg_insert
+from sqlmodel import Session
+
+from infrastructure.postgres.property_table import PropertyRow
+from repositories.property.property_identity_writer import (
+    PropertyIdentityInsert,
+    PropertyIdentityWriter,
+)
+
+
+class PropertyIdentityWriterPostgresRepository(PropertyIdentityWriter):
+    def __init__(self, session: Session) -> None:
+        self._session = session
+        # SQLModel injects ``__table__`` at runtime on table=True classes but the
+        # stubs don't expose it; pin to ``Table`` so the dialect insert is typed.
+        self._table: Table = cast(Table, getattr(PropertyRow, "__table__"))
+
+    def insert_all(self, rows: list[PropertyIdentityInsert]) -> int:
+        if not rows:
+            return 0
+
+        values = [
+            {
+                "portfolio_id": r.portfolio_id,
+                "creation_status": r.creation_status,
+                "uprn": r.uprn,
+                "landlord_property_id": r.landlord_property_id,
+                "address": r.address,
+                "postcode": r.postcode,
+                "user_inputted_address": r.user_inputted_address,
+                "user_inputted_postcode": r.user_inputted_postcode,
+                "lexiscore": r.lexiscore,
+            }
+            for r in rows
+        ]
+
+        stmt = pg_insert(self._table).values(values)
+        # Matches `uq_property_portfolio_uprn` (partial: WHERE uprn IS NOT NULL).
+        stmt = stmt.on_conflict_do_nothing(
+            index_elements=["portfolio_id", "uprn"],
+            index_where=self._table.c.uprn.isnot(None),
+        )
+
+        # SQLModel re-exports SQLAlchemy's Session.execute; one overload is marked
+        # deprecated in the stubs but the INSERT path is supported.
+        result = self._session.execute(stmt)  # pyright: ignore[reportDeprecated]
+        return cast(int, result.rowcount)
diff --git a/repositories/property/property_postgres_repository.py b/repositories/property/property_postgres_repository.py
index 55a32ed3..6226e1e9 100644
--- a/repositories/property/property_postgres_repository.py
+++ b/repositories/property/property_postgres_repository.py
@@ -25,9 +25,12 @@ class PropertyPostgresRepository(PropertyRepository):
         if row is None:
             raise ValueError(f"property {property_id} not found")
         identity = PropertyIdentity(
+            # `postcode`/`address` are nullable in the FE schema (the finaliser may
+            # insert a row with neither); coerce the degenerate null to "" so the
+            # identity type stays a plain str.
             portfolio_id=row.portfolio_id,
-            postcode=row.postcode,
-            address=row.address,
+            postcode=row.postcode or "",
+            address=row.address or "",
             uprn=row.uprn,
             landlord_property_id=row.landlord_property_id,
         )
@@ -53,8 +56,8 @@ class PropertyPostgresRepository(PropertyRepository):
                 Property(
                     identity=PropertyIdentity(
                         portfolio_id=row.portfolio_id,
-                        postcode=row.postcode,
-                        address=row.address,
+                        postcode=row.postcode or "",
+                        address=row.address or "",
                         uprn=row.uprn,
                         landlord_property_id=row.landlord_property_id,
                     ),