2027 Tax Deadlines Calendar for Accounting Firms (Tax Year 2026)
Every key federal deadline for the 2026 tax year filed in 2027, with exact weekdays, plus the internal client document deadlines accounting firms should set for each one.
Quick answer: For the 2026 tax year, filed in 2027, the key federal deadlines for calendar-year taxpayers are: February 1, 2027 for W-2s and Form 1099-NEC, March 15, 2027 for partnership (Form 1065) and S corporation (Form 1120-S) returns, April 15, 2027 for individual (Form 1040) and C corporation (Form 1120) returns, September 15, 2027 for extended partnership and S corporation returns, and October 15, 2027 for extended individual and C corporation returns.
This calendar is written for accounting, bookkeeping and tax firms. Alongside each IRS deadline, it shows what your firm needs from clients, and when to ask for it.
Key takeaways
- January 31, 2027 falls on a Sunday, so W-2 and 1099-NEC deadlines move to Monday, February 1, 2027.
- March 15, 2027 is a Monday, so pass-through returns are due on March 15 itself. (In 2026 they were due March 16, because March 15 fell on a Sunday. Some published 2027 calendars carried that date over by mistake.)
- April 15, 2027 is a Thursday, and the individual filing deadline stays on that date.
- Every client-facing deadline should have an internal document deadline four to six weeks earlier.
2027 federal tax deadlines at a glance
| Date | Deadline | Who it affects |
|---|---|---|
| Friday, January 15, 2027 | Fourth-quarter 2026 estimated tax payment (Form 1040-ES) | Self-employed individuals, investors, anyone paying estimates |
| Monday, February 1, 2027 | Furnish and file Forms W-2; furnish and file Form 1099-NEC | Employers and businesses paying contractors |
| Mid-February 2027 | Many brokerage statements (Forms 1099-B and consolidated 1099s) due to recipients | Investment account holders |
| Monday, March 15, 2027 | Form 1065 and Form 1120-S due; Schedule K-1s to owners; Form 7004 extension deadline for these returns | Partnerships, multi-member LLCs taxed as partnerships, S corporations |
| Thursday, April 15, 2027 | Form 1040 and Form 1120 due; Form 4868 and Form 7004 extension deadline; first-quarter 2027 estimated payment; last day for 2026 IRA and HSA contributions | Individuals, sole proprietors, C corporations |
| Tuesday, June 15, 2027 | Second-quarter 2027 estimated payment; deadline for US taxpayers living abroad (automatic two-month extension) | Estimated-tax payers, US citizens and residents abroad |
| Wednesday, September 15, 2027 | Extended Form 1065 and Form 1120-S due; third-quarter 2027 estimated payment | Extended partnerships and S corporations; estimated-tax payers |
| Friday, October 15, 2027 | Extended Form 1040 and Form 1120 due | Extended individuals and C corporations |
Dates apply to calendar-year filers and assume no disaster-related postponement. The IRS regularly postpones deadlines for taxpayers in federally declared disaster areas, so check for relief that applies to specific clients. Fiscal-year entities have deadlines keyed to their own year end.
Why the weekday matters
When a federal due date falls on a Saturday, Sunday or legal holiday, the deadline moves to the next business day. That rule changes several dates from year to year, and it's a common source of errors in reused calendars.
- January 31, 2027 is a Sunday, so W-2 and 1099-NEC deadlines move to February 1.
- March 15, 2027 is a Monday, so there is no shift. If you're working from a 2026 calendar that shows March 16, update it.
- April 15, 2027 is a Thursday, so the individual deadline stays put.
Month-by-month: what your firm should be doing
October to December 2026: prepare
- Finalize engagement letters for the coming season, including your document cutoff date and extension policy.
- Review last year's returns to build each client's personalized document list.
- Confirm year-end planning items with clients: estimated payments, retirement contributions and major transactions.
- Check your own written information security plan and renew software licenses.
- Send year-end reminders to business clients about W-2 and 1099-NEC obligations and collecting contractor W-9s.
January 2027: request
- Early January: send every client a personalized document request. Our document request email templates are ready to use.
- January 15: remind clients who pay estimates about the fourth-quarter payment.
- Help business clients prepare W-2s and 1099-NECs ahead of the February 1 deadline.
February 2027: collect and check
- February 1: W-2 and 1099-NEC deadline. Most individual clients will have their wage forms within days.
- Review documents as they arrive. Catch wrong years, missing pages and unreadable scans immediately.
- Watch for corrected 1099s from brokerages, which commonly follow the originals.
- Mid-February: set the internal document deadline for partnership and S corporation clients, so you have time before March 15.
March 2027: pass-through deadline
- March 15: file Forms 1065 and 1120-S, or Form 7004 extensions, and issue K-1s.
- Early March: your internal document cutoff for individual clients, if you're using a six-week buffer.
- Follow up on every individual client still missing documents, naming exactly what's outstanding.
April 2027: individual deadline
- File extensions for every client with incomplete documents, with payment estimates for those likely to owe.
- April 15: file Forms 1040 and 1120 or extensions, and remind clients of first-quarter 2027 estimates and last-day IRA and HSA contributions.
May to October 2027: extended season
- Set new internal deadlines for extended clients and keep following up monthly.
- June 15: second-quarter estimates, and the automatic deadline for clients living abroad.
- September 15: extended pass-through returns and third-quarter estimates.
- October 15: extended individual and C corporation returns. There's no further automatic extension for most filers.
Build internal deadlines backward from IRS deadlines
An IRS deadline is when a return must be filed. It is not when you need the documents. Work backward from each filing deadline, subtracting the time needed for preparation, review and client sign-off:
| IRS deadline | Suggested client document deadline | Suggested extension decision date |
|---|---|---|
| March 15, 2027 (Forms 1065, 1120-S) | February 12, 2027 | March 1, 2027 |
| April 15, 2027 (Forms 1040, 1120) | March 1, 2027 | April 1, 2027 |
| September 15, 2027 (extended pass-throughs) | July 30, 2027 | Not applicable |
| October 15, 2027 (extended 1040, 1120) | August 31, 2027 | Not applicable |
These are starting points. Adjust them for your capacity and client mix, then publish them to clients in your engagement letters and requests.
Penalties for missing a deadline
Missing a filing deadline without an extension usually triggers the failure-to-file penalty: 5% of the unpaid tax per month, up to 25%, according to the IRS. Partnership and S corporation returns carry their own late-filing penalty, charged per owner for each month the return is late, as described on the IRS failure to file penalty page. That penalty applies even when no tax is due, which makes on-time filing or extension especially important for pass-through clients. For a full breakdown, see our guide to tax extensions and penalties.
State deadlines
Most states align their individual income tax deadlines with the federal April date, but not all do, and business return and extension rules vary. Add each client's state deadlines to your firm calendar alongside the federal ones.
Make the calendar work for you
Deadlines rarely slip because a firm didn't know the date. They slip because documents arrived late or incomplete. Correctdocs sends each client one secure request link, checks each upload as it arrives, and follows up automatically by text and email until everything is in.
Correctdocs is in early access. The first 10 US accounting, bookkeeping and tax firms get a free 30-day pilot on real client requests. Request early access.
Frequently asked questions
When are 2026 taxes due?
Individual income tax returns for the 2026 tax year are due Thursday, April 15, 2027 for calendar-year filers. With an extension filed by that date, the deadline moves to Friday, October 15, 2027.
When are partnership and S corporation returns due in 2027?
Calendar-year Forms 1065 and 1120-S for the 2026 tax year are due Monday, March 15, 2027. An extension on Form 7004 moves the deadline to Wednesday, September 15, 2027.
When do W-2s and 1099-NECs have to be sent in 2027?
The statutory date is January 31, which falls on a Sunday in 2027, so the deadline is Monday, February 1, 2027.
When is the last 2026 estimated tax payment due?
The fourth-quarter 2026 estimated tax payment is due Friday, January 15, 2027.
Can I still contribute to an IRA for 2026 in 2027?
Yes. Contributions for the 2026 tax year can generally be made until the April 15, 2027 filing deadline. A filing extension does not extend this contribution deadline.
Sources
- IRS, Form 4868 and instructions
- IRS, About Form 7004
- IRS, Failure to file penalty
- IRS, Topic no. 653, penalties and interest charges
This calendar is general information for calendar-year filers, not tax advice. Deadlines can change because of legislation or disaster relief, so confirm dates with the IRS and your state tax agency.