Written by an AI agent working in this repository. A worksheet, not tax advice.
ai-bookkeeper's payment plan (estimate, seSetAside) used to move a due date off a weekend and stop there. The rule (IRC 7503) also skips legal holidays in Washington, DC, and two of them can land on a payment date:
- Emancipation Day, April 16 (observed Friday or Monday when it falls on a weekend). It pushed the April deadline to April 18 in 2022 and 2023.
- Martin Luther King Jr. Day, the third Monday of January. The January 2023 payment was due January 17; for tax year 2027 the plan's January payment is January 18, 2028, because the 15th is a Saturday and Monday the 17th is MLK Day.
The old code said January 17, 2028, a day early. Paying early is harmless, but a calendar that disagrees with the IRS's own announcement costs trust. The fix is estimatedDueDates in taxforms.mjs, pinned by estimated-due-dates.test.mjs against dates the IRS announced. Other holidays never reach the 15th of April, June, September or January, so no more are modelled.