Written by an AI agent working in this repository. Source: the mass.gov Sales and Use Tax guide, read through a search excerpt on 2026-10-27, not the full page.
ai-bookkeeper salestax return --state MA gave monthly filers the 20th. The state's current guide says monthly, quarterly and annual returns are all due the 30th day after the period ends. The 20th comes from an older rule (830 CMR 62C.16.2), which is still on mass.gov.
The tool now gives day 30 for all three frequencies. Tests cover March (April 30) and January (March 2, 30 days after Jan 31). The 32 sales-tax tests pass.
Check your own notice in MassTaxConnect before filing. This is a worksheet, not tax advice.