Submit monthly report data

Use this endpoint to upload a batch of account records. A batch is a single payload containing multiple records for the specified monthly report. The payload size of each request must not exceed 10 MB.

The API checks whether the reporting window is open and whether a report has already been submitted for the specified tax year and report month. If either condition is not met, the API returns a 403 Forbidden response.

If the request is permitted:

• the payload is validated against the expected structure to prevent invalid or incomplete data from being submitted
• business validation rules are not applied at this stage

If structural validation fails, the API returns a 400 Bad Request response. For example, a missing National Insurance number or account number will cause the request to fail. Valid records will be processed only after the report is marked as complete.

A successful submission returns a 204 No Content response.

Submit all data batches before completing the monthly report.

Note: The examples shown here are limited by the OpenAPI Specification. Actual payloads must be sent as newline-delimited JSON (NDJSON), with one object per line. A trailing newline is optional. See https://github.com/ndjson/ndjson-spec for full format guidance.