Massachusetts Form M-990T: Filing, Extension, and Payment Deadlines

Three dates, not one

Massachusetts Form M-990T is the state’s return for unrelated business income of an otherwise tax-exempt corporation, filed with the Department of Revenue under M.G.L. c. 62C and c. 63B. For a 2025 calendar-year filer, current DOR guidance establishes three distinct dates that are frequently compressed into one in casual descriptions: the original filing deadline, the original payment deadline, and the extended filing deadline available only with a valid extension.

Both the original filing deadline and the original payment deadline for a 2025 calendar-year filer are April 15, 2026. The extended filing deadline — available only when the taxpayer has obtained a valid extension — is December 15, 2026.

What the extension actually extends

The critical distinction is that an extension to file is not an extension to pay. DOR’s current Form M-990T instructions state directly that payment in full for a 2025 calendar-year filer is due April 15, 2026, and that an extension concerns filing only. A taxpayer who obtains a valid extension may submit the completed return as late as December 15, 2026 without being treated as filing late — but the tax itself, if any is owed, was still due on April 15, 2026, and unpaid amounts begin accruing exposure to penalties and interest from that original date, not from December 15.

Stated the safe way: "For a 2025 calendar-year filer, April 15, 2026 is both the original filing and payment deadline. December 15, 2026 is the extended filing deadline only if a valid extension was obtained — it does not extend the payment deadline." Describing December 15 as "the deadline" without that qualification risks a founder assuming they have until December to pay, which is not correct.

Estimated payments still apply

Form M-990T generally carries no separate filing fee, but estimated tax is generally required when the expected excise exceeds $1,000, with penalties and interest for underpayment — tracked through the UBI-ES estimated-payment process alongside the return itself. An organization expecting meaningful unrelated business income should not wait until April 15 to address its liability for the first time; estimated payments during the year are a separate, ongoing obligation from the annual return.

What a fiscal-year filer does instead

The two dates above are specific to a 2025 calendar-year filer. The rule underneath them is reusable: Form M-990T is due on the 15th day of the fourth month after the close of the taxable year, which produces April 15 only because a calendar year closes on December 31. A fiscal-year filer counts four months from its own year end and takes the 15th of that month, rather than assuming the calendar-year dates shift by a fixed offset.

A fiscal-year filer should therefore apply the general shape of the rule, that the original filing and payment deadlines coincide and that a valid extension moves filing only and never payment, to the dates its own formula produces. Trusts and unincorporated associations use a different return and due-date regime entirely, which this article does not cover.