Q4 2026 IRS calendar map

This quarter hub organizes the October through December tax-calendar rows that remain ahead in the 2026 cycle. It is especially useful because Q4 mixes tax deadlines with major holiday and service-closure questions. The tax rows should stay tied to the IRS fourth-quarter calendar, while holiday closure questions should stay tied to OPM, USPS, Federal Reserve, bank, and local-service sources.

How Q4 differs from the holiday calendar

October, November, and December are easy to confuse because the same months contain federal holidays, postal holidays, Federal Reserve holidays, payroll deposit rows, extension-return rows, and year-end business items. The IRS fourth-quarter calendar is the source for tax rows. OPM, USPS, and Federal Reserve sources are the sources for holiday and service context. A reader should not use one source family to answer the other family’s question.

That distinction protects the page from overpromising. October 12 Columbus Day does not decide the October 15 IRS extension-return date. Veterans Day and Thanksgiving do not decide whether a third-quarter business form was filed. Christmas Day does not decide whether a December 15 corporate estimated-tax installment or a December 31 Form 2290/Form 730 row applies.

Q4 verification checklist

• Open the IRS fourth-quarter tax calendar and confirm the month and date before using a row.
• Check extension status, form type, quarter, payment period, first-use month, wagering month, payroll deposit schedule, and business entity type.
• Check bank, payroll, EFTPS, and provider cutoffs before the visible IRS date if payment timing matters.
• Check OPM, USPS, Federal Reserve, local offices, and private institutions separately for holiday-service questions.
• Recheck the source if a disaster-relief notice, IRS update, bank notice, or service alert appears after the last verified date.

What this page does not decide

This Q4 hub does not decide whether a reader has a valid extension, whether a return is complete, whether an entity is covered by a form, whether a payroll deposit rule applies, whether a nonresident alien return is required, whether a partnership payment voucher applies, whether tax-exempt organization UBIT estimated tax applies, or whether a late filing or late payment penalty exists.

It also does not decide bank operations, postal operations, or private-employer schedules around Columbus Day, Veterans Day, Thanksgiving, or Christmas. Those questions have their own source-reviewed pages because the controlling sources are different.