CW-048 · ประกันสังคม monthly filing (สปส. 1-10)

Priority P1 · Area payroll · Estimate M · Phase 3

What to build

A payroll officer picks a month and downloads a สปส. 1-10 file ready to submit to the Social Security Office. Payroll already computes both halves of the contribution under มาตรา 33 and stores them on every payslip as ssoEmployee and ssoEmployer; there is currently no way to get them out.

This runs alongside the withholding-tax chain rather than after it — it shares the export seam and nothing else.

Acceptance criteria

• The export for the seeded demo company matches hand-computed employee and employer totals.
• The layout matches the Social Security Office's published specification.
• The contribution ceiling is applied per employee per month, with tests at the boundary.
• An employee with no social security number is reported as an error naming them, rather than silently omitted or exported blank.
• A period that does not reconcile produces the error from #43, not a file.

Blocked by

• #43 — reconciliation, permission, download and audit come from there.

Not blocked by the ภ.ง.ด.1 chain; these can be worked in parallel. The rules being formatted here have not been reviewed by anyone qualified — see #36.

No files or entry points are named. Start by tracing the existing payroll export seam and the payslip fields ssoEmployee and ssoEmployer, then read #43 and the Social Security Office specification. Done means producing a compliant file, enforcing the ceiling and missing-number error, and refusing unreconciled periods.