diff --git a/pyproject.toml b/pyproject.toml
index ea1e34a..2c4508d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "transaction-tracker"
-version = "0.1.0"
+version = "0.1.3"
 description = ""
 authors = [
     {name = "Aaron Guise",email = "aaron@guise.net.nz"}
diff --git a/scripts/migrate_ttl.py b/scripts/migrate_ttl.py
new file mode 100644
index 0000000..d3c8872
--- /dev/null
+++ b/scripts/migrate_ttl.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+"""
+Migrate existing transaction records to a new TTL.
+
+Reads all .json record files in the given storage directory and rewrites
+expires_at to processed_at + ttl_days. Records that have already expired
+are left untouched (they will be cleaned up on next startup).
+
+Usage:
+    python migrate_ttl.py <storage_dir> <ttl_days>
+
+Example (run on the server):
+    python migrate_ttl.py /opt/data/transaction_records 14
+"""
+import json
+import os
+import sys
+from datetime import datetime, timedelta
+
+
+def migrate(storage_dir: str, ttl_days: int) -> None:
+    if not os.path.isdir(storage_dir):
+        print(f"Directory not found: {storage_dir}")
+        sys.exit(1)
+
+    now = datetime.now()
+    updated = skipped = errors = 0
+
+    for filename in os.listdir(storage_dir):
+        if not filename.endswith(".json"):
+            continue
+        path = os.path.join(storage_dir, filename)
+        try:
+            with open(path) as f:
+                record = json.load(f)
+
+            processed_at = datetime.fromisoformat(record["processed_at"])
+            current_expires = datetime.fromisoformat(record["expires_at"])
+
+            if current_expires <= now:
+                skipped += 1
+                continue
+
+            new_expires = processed_at + timedelta(days=ttl_days)
+            if new_expires <= current_expires:
+                skipped += 1
+                continue
+
+            record["expires_at"] = new_expires.isoformat()
+            with open(path, "w") as f:
+                json.dump(record, f)
+            updated += 1
+
+        except (json.JSONDecodeError, KeyError, ValueError, OSError) as e:
+            print(f"  ERROR {filename}: {e}")
+            errors += 1
+
+    print(f"Done: {updated} updated, {skipped} skipped (already expired or TTL already sufficient), {errors} errors")
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 3:
+        print(__doc__)
+        sys.exit(1)
+    migrate(sys.argv[1], int(sys.argv[2]))
diff --git a/tests/test_transact_cache.py b/tests/test_transact_cache.py
index 3a3de7f..2f32bd1 100644
--- a/tests/test_transact_cache.py
+++ b/tests/test_transact_cache.py
@@ -215,6 +215,43 @@ class TestTransactionProcessor:
         with pytest.raises(TransactionAlreadyProcessedError):
             multi_decorated("multi_1", 100.00)
 
+    def test_is_processed_respects_expiry_without_cleanup(self, temp_dir):
+        """Expired record must not block re-processing even if cleanup hasn't run.
+
+        This is the regression test for the bug where is_processed() only checked
+        file existence. cleanup_expired() runs at startup and deletes expired files,
+        but if the expired file is deleted AFTER a duplicate arrives in the same run
+        the duplicate would slip through. The fix: is_processed() reads expires_at
+        from the JSON directly.
+        """
+        import json
+
+        processor = TransactionProcessor(storage_dir=temp_dir, ttl_days=1)
+
+        @processor.unique_transaction()
+        def pay(transaction_id, amount):
+            return "ok"
+
+        pay("ttl_check", 50.0)
+
+        record_path = os.path.join(temp_dir, "ttl_check.json")
+        assert os.path.exists(record_path)
+
+        # Manually backdate expires_at so the record is expired
+        with open(record_path) as f:
+            record = json.load(f)
+        record["expires_at"] = (datetime.now() - timedelta(seconds=1)).isoformat()
+        with open(record_path, "w") as f:
+            json.dump(record, f)
+
+        # is_processed must return False — the file still exists but it's expired
+        assert not processor.tracker.is_processed("ttl_check")
+
+    def test_is_processed_returns_true_for_valid_record(self, processor):
+        """is_processed returns True for a record that exists and has not expired."""
+        processor.tracker.mark_processed("valid_tx")
+        assert processor.tracker.is_processed("valid_tx")
+
     def test_non_string_transaction_id(self, processor):
         """Test handling of non-string transaction IDs."""
 
diff --git a/transaction_tracker/__init__.py b/transaction_tracker/__init__.py
index 6ef5b8b..390b864 100644
--- a/transaction_tracker/__init__.py
+++ b/transaction_tracker/__init__.py
@@ -40,9 +40,17 @@ class TransactionTracker:
         self.logger.debug(f"Transaction {transaction_id} marked as processed")
 
     def is_processed(self, transaction_id):
-        """Check if transaction was already processed."""
+        """Check if transaction was already processed and its record has not expired."""
         record_path = os.path.join(self.storage_dir, f"{transaction_id}.json")
-        return os.path.exists(record_path)
+        if not os.path.exists(record_path):
+            return False
+        try:
+            with open(record_path, "r") as f:
+                record = json.load(f)
+            expires_at = datetime.fromisoformat(record["expires_at"])
+            return datetime.now() < expires_at
+        except (json.JSONDecodeError, KeyError, ValueError, TypeError):
+            return False
 
     def require_unique_transaction(self, id_arg='transaction_id'):
         """