2026 due dates, filing frequencies, form OS-114, and official filing resources.
Monthly Connecticut sales tax returns are due the last day of the month following the period. Quarterly returns are due the last day of the month following the period (Apr 30 / Jul 31 / Oct 31 / Jan 31). When a due date lands on a weekend or federal holiday it moves to the next business day; the 2026 calendar on this page already applies that adjustment.
Choose the calculation engine or the compliance workflow. Inspect the public examples, then bring five cases from your business.
Trace a generated sample return to its source rows. See how seller sales, marketplace activity and unresolved responsibility are separated.
Trace the sample return →Synthetic Virginia package demonstration. Review, authorization and state acceptance remain separate steps.
Evaluate sales tax compliance →Prefer to use your AI agent? Give it the evaluation brief →
See task rates and subscription prices. Public evidence is open to inspect; we confirm scope and commercial terms before a private evaluation.
Every date below comes from the state's published deadline rule (dataset 2026.07.0) and is already moved to the next business day when it lands on a weekend or federal holiday. Your account's assigned filing frequency decides which table applies.
Rule: Last day of the month following the period.
| Period | Period ends | Return due |
|---|---|---|
| January 2026 | Jan 31, 2026 | Mar 2, 2026 (moved: 2026-02-28 falls on a Saturday) |
| February 2026 | Feb 28, 2026 | Mar 31, 2026 |
| March 2026 | Mar 31, 2026 | Apr 30, 2026 |
| April 2026 | Apr 30, 2026 | Jun 1, 2026 (moved: 2026-05-31 falls on a Sunday) |
| May 2026 | May 31, 2026 | Jun 30, 2026 |
| June 2026 | Jun 30, 2026 | Jul 31, 2026 |
| July 2026 | Jul 31, 2026 | Aug 31, 2026 |
| August 2026 | Aug 31, 2026 | Sep 30, 2026 |
| September 2026 | Sep 30, 2026 | Nov 2, 2026 (moved: 2026-10-31 falls on a Saturday) |
| October 2026 | Oct 31, 2026 | Nov 30, 2026 |
| November 2026 | Nov 30, 2026 | Dec 31, 2026 |
| December 2026 | Dec 31, 2026 | Feb 1, 2027 (moved: 2027-01-31 falls on a Sunday) |
Rule: Last day of the month following the period (Apr 30 / Jul 31 / Oct 31 / Jan 31).
| Period | Period ends | Return due |
|---|---|---|
| Q1 2026 | Mar 31, 2026 | Apr 30, 2026 |
| Q2 2026 | Jun 30, 2026 | Jul 31, 2026 |
| Q3 2026 | Sep 30, 2026 | Nov 2, 2026 (moved: 2026-10-31 falls on a Saturday) |
| Q4 2026 | Dec 31, 2026 | Feb 1, 2027 (moved: 2027-01-31 falls on a Sunday) |
Rule: January 31 following the calendar year.
| Period | Period ends | Return due |
|---|---|---|
| Calendar year 2026 | Dec 31, 2026 | Feb 1, 2027 (moved: 2027-01-31 falls on a Sunday) |
The principal repository-tracked return is OS-114. Paper eligibility is taxpayer-specific; electronic filing or a waiver may control.
Tracked form version: OS-114, Rev. 07/2026 (revision code 0726)
Paper filing posture: taxpayer specific
Prophit.ai tracks every Connecticut due date above inside the return workspace, builds the period from your transaction data, and produces worksheet for portal entry and portal upload file that a reviewer approves before anything is submitted.
Need every state at once? Download the 2026 sales tax filing calendar (CSV + ICS, all states, weekend/holiday-adjusted).
Workflow support does not by itself establish registration, filing authority, credentials, agency acceptance, or tax advice. Confirm your assigned filing frequency with the state.
Monthly Connecticut sales tax returns are due the last day of the month following the period. Quarterly returns are due the last day of the month following the period (Apr 30 / Jul 31 / Oct 31 / Jan 31). When a due date lands on a weekend or federal holiday it moves to the next business day; the 2026 calendar on this page already applies that adjustment.
Connecticut assigns a filing frequency to each account. The published cadences are monthly, quarterly and annual filing; the state assigns the frequency based on tax volume and notifies the account, so confirm the assigned basis before relying on a calendar.
The Connecticut return tracked here is OS-114. The principal repository-tracked return is OS-114. Paper eligibility is taxpayer-specific; electronic filing or a waiver may control.
The due date moves to the next business day. In 2026, 7 of the Connecticut due dates listed on this page are adjusted for a weekend or federal holiday; each adjusted date is marked in the calendar.
Paper filing posture tracked for Connecticut: taxpayer specific. The principal repository-tracked return is OS-114. Paper eligibility is taxpayer-specific; electronic filing or a waiver may control.
Reviewed and current as of October 26, 2026. Read the full Connecticut sales tax guide for rates, sourcing, products, exemptions, and marketplace rules.
