CW-046 · ภ.ง.ด.1ก annual withholding summary

Priority P1 · Area payroll · Estimate S · Phase 3

Parent

#3 (CW-004).

What to build

A payroll officer picks a tax year and downloads ภ.ง.ด.1ก, the annual summary every Thai employer files. It is the year's monthly filings added up, so it reuses the aggregation and the rounding rules from #44 and differs in layout.

Acceptance criteria

• The annual export equals the sum of the twelve monthly exports for the same year — asserted by a test, not by inspection.
• The layout matches the published specification.
• An employee who joined or left mid-year appears with the months they were actually paid.
• A year with a month that does not reconcile is refused, naming the month.

Blocked by

• #44 — the aggregation and rounding rules are built there, and duplicating them is how the two filings end up disagreeing.

If this is wanted sooner it can be unblocked and worked alongside #44, at the cost of writing the aggregation twice and reconciling it afterwards.

Start by reading #44 to understand the aggregation and rounding rules, then locate the existing monthly export entry point and its tests. Define the annual export against the published layout, covering mid-year employment, twelve-month equality, and reconciliation failures that name the month; completion requires tests for these acceptance criteria.