Small Business Tax Calendar 2026: Every Deadline You Need to Know

Q4 2025 Estimated Tax Payment Due

Your fourth and final estimated tax payment for 2025 income. Pay via IRS Direct Pay or EFTPS. If you skip this and wait until April, you owe the underpayment penalty on the shortfall — currently around 8% annualized. You can skip this payment if you file and pay your full 2025 tax return by February 2, 2026.

Penalty: ~8% annualized underpayment

W-2s to Employees + 1099-NECs to Contractors

Employees must receive Form W-2 by January 31. Contractors who received $600 or more in 2025 must receive Form 1099-NEC by January 31. This is also the deadline to file 1099-NECs with the IRS. Get payee TINs (W-9s) before year-end — chasing them in January is a losing battle.

Penalty: $60–$310/form depending on how late

1099-MISC and Other Information Returns (Paper)

Paper copies of most 1099 forms (excluding 1099-NEC) are due to the IRS by February 28. If filing electronically, the deadline extends to March 31. If you issued royalties, paid rents, or paid attorneys more than $600, this applies to you. Electronic filing is strongly recommended — it's easier, and the penalty for filing incorrect information returns is the same regardless of method.

Penalty: $60–$310/form

S-Corporation (Form 1120-S) and Partnership (Form 1065) Returns

S-corps and partnerships file on March 15 — one month before individuals. This isn't a coincidence: shareholders and partners need their K-1s before they can complete their own returns by April 15. If you need more time, file Form 7004 by March 15 to extend to September 15. The extension covers filing, not payment — estimated tax is still due March 15.

Penalty: $245/partner or shareholder/month, up to 12 months

1099-MISC and Other Information Returns (Electronic)

Electronic filing deadline for most 1099s except 1099-NEC. If you use payroll software or a bookkeeper, this is typically handled automatically. If you're doing it yourself, IRS FIRE system or an approved third-party transmitter is required.

Form 1040 / Schedule C — Individual Income Tax Return

Your complete individual income tax return including Schedule C (profit or loss from business). All income, deductions, and self-employment tax are calculated here. If you can't file by April 15, file Form 4868 for an automatic 6-month extension to October 15. The extension is for filing only — if you owe tax, it was due April 15. Paying late triggers the failure-to-pay penalty (0.5%/month) on top of interest.

Penalty: 5%/month on unpaid tax (failure-to-file); 0.5%/month (failure-to-pay)

Q1 2026 Estimated Tax Payment

First estimated tax payment for 2026 income. If your business earned income January through March, the estimated tax on that income is due April 15. The safe harbor rule: pay either 90% of your 2026 tax liability or 100% of your 2025 tax liability (110% if 2025 AGI was above $150,000), whichever is smaller, across four payments — and you avoid underpayment penalties even if you owe a balance in April 2027.

Penalty: ~8% annualized underpayment

C-Corporation Tax Return (Form 1120)

Calendar-year C-corps file by April 15. If you need more time, file Form 7004 for a 6-month extension to October 15. Fiscal-year C-corps file by the 15th of the fourth month after their fiscal year ends.

Penalty: 5%/month on unpaid tax, up to 25%

Form 941 — Q1 Payroll Tax Return

Form 941 reports wages paid, federal income tax withheld, and Social Security/Medicare taxes for Q1 (January–March). Due April 30. Note that your actual payroll tax deposits happen on a more frequent schedule — semiweekly or monthly depending on your total payroll tax liability. Form 941 is the quarterly report that reconciles those deposits.

Penalty: 2–15% of tax not deposited on time

Q2 2026 Estimated Tax Payment

Second estimated payment for 2026, covering April and May income. Note the "oddly short" Q2 window: Q1 runs January–March (3 months), Q2 runs only April–May (2 months). This trips up a lot of first-year business owners. June 16 is the standard date because June 15 falls on a Sunday in 2026.

Penalty: ~8% annualized underpayment on shortfall

Form 941 — Q2 Payroll Tax Return

Payroll tax report for Q2 wages (April–June). Same mechanics as Q1 filing: reconciles your biweekly or monthly deposit schedule. If your total payroll tax liability is under $1,000 for the year, you may qualify for annual Form 944 filing instead — check with your payroll provider.

FUTA (Federal Unemployment Tax) Deposit — Q2

If your Federal Unemployment Tax Act (FUTA) liability exceeded $500 in the first half of the year, a deposit is due by August 1 (last day of the month following Q2 end). If total FUTA liability is under $500, you carry it forward to next quarter. FUTA is paid entirely by the employer — never withheld from employees.

Q3 2026 Estimated Tax Payment

Third estimated payment for 2026, covering June through August income (3 months, back to the normal window). At this point in the year, you should have a good picture of your annual income — this is a good time to recalculate your estimate and adjust if your income changed significantly from Q1/Q2.

Penalty: ~8% annualized underpayment on shortfall

Extended S-Corp (Form 1120-S) and Partnership (Form 1065) Returns

Final deadline for S-corp and partnership returns that were extended. K-1s to shareholders and partners were supposed to be issued by this date — late K-1s delay your partners' and shareholders' own returns and can result in amended filings. Extended returns are common when partnerships have complex multi-state activities or late-arriving information from other entities.

Penalty: $245/partner or shareholder/month after deadline

Extended Individual Returns (Form 1040) — Hard Deadline

The absolute last day to file your 2025 individual return. No further extensions are available. If you owe and haven't paid, the failure-to-pay penalty has been accruing since April 15 — filing now stops the failure-to-file penalty (5%/month) but doesn't retroactively eliminate the interest and payment penalties that already accrued. Pay anything owed immediately.

Hard deadline — no extension available after this date

Extended C-Corporation Returns (Form 1120)

Final filing deadline for calendar-year C-corps on extension. Same principle applies: extension is for the return, not the payment. Any tax owed was due April 15 — interest and failure-to-pay penalties have been accruing since then.

Form 941 — Q3 Payroll Tax Return

Payroll tax report for Q3 wages (July–September). Three more months of payroll reconciled. If you haven't made a required payroll deposit at any point this year, correct it before this filing — accuracy matters more once you're in Q4 and IRS notices start arriving for the year.

Year-End Planning Cutoff — Section 179, Retirement, Depreciation

December 31 is the last day for actions that affect your 2026 tax year. This includes: purchasing and placing in service equipment eligible for Section 179 expensing or bonus depreciation; making contributions to a Solo 401(k) (employee contributions must be made by December 31 — employer contributions can wait until your tax filing deadline); timing deductible business expenses; and writing off uncollectible bad debts if you're on accrual basis. The window closes at midnight.

Miss this: permanent loss of 2026 tax-year deductions

Collect W-9s from All Contractors Paid $600+

You need a completed W-9 (name, address, TIN) from every contractor you paid $600 or more this year before you can issue their 1099-NEC in January. Chasing W-9s in January is painful — people are slow, TINs are wrong, and you risk missing the January 31 deadline. Collect them before payment or at the latest by December 31.