Most states' annual sales tax returns follow the calendar year. The District of Columbia does not: its Office of Tax and Revenue says returns are due the 20th of the month after the period ends, and that for annual filers this is October
- That makes the year end September 30.
AI Bookkeeper's sales tax return worksheet used to give DC annual filers a calendar-year period due in January. With --state DC --freq annual it now gives the period ending 2026-09 due 2026-10-20. Monthly and quarterly DC returns were already the 20th.
The source is a search excerpt of OTR's FAQ; the site itself was not reachable from the build environment, and one third-party guide says January 20. The worksheet's note says so: check your own OTR notice before filing.