Small Business Tax Calendar 2025: Every Filing Deadline

By Yarik Yarosh, CPA ·September 5, 2026 ·Updated October 4, 2026 ·6 min read

Written by Yarik Yarosh, CPA (US & Canada) September 5, 2026 · FL CPA license AC61704 · CPA Ontario

Missing a tax deadline costs money. Late filing penalties, late payment penalties, and interest compound quickly. A single missed Form 941 deadline can generate a 10% penalty on the unpaid tax. A missed estimated tax payment triggers an underpayment penalty that runs from the due date until the tax is paid. This calendar covers every major federal deadline for small businesses in 2025.

✓Key takeaway

2025 federal tax deadlines:

January 2025:

January 15: Q4 2024 estimated tax payment due (Form 1040-ES)
January 31: W-2s due to employees
January 31: 1099-NEC due to recipients AND to the IRS (no automatic extension)
January 31: Form 941 (Q4 2024 payroll tax return) due
January 31: Form 940 (annual FUTA return) due
January 31: 1099-MISC due to recipients (due to IRS by February 28 paper / March 31 electronic)

February 2025:

February 28: 1099-MISC, 1099-INT, 1099-DIV due to IRS (paper filing)

March 2025:

March 15: S-Corp return (Form 1120-S) due (or extension Form 7004)
March 15: Partnership return (Form 1065) due (or extension Form 7004)
March 15: K-1s due to shareholders/partners
March 15: Form 2553 (S-Corp election) due for existing entities wanting S-Corp status for 2025
March 31: 1099-MISC, 1099-INT, 1099-DIV due to IRS (electronic filing)
March 31: 1099-K due to IRS (electronic filing)

April 2025:

April 15: Individual return (Form 1040) due (or extension Form 4868)
April 15: C-Corp return (Form 1120) due for calendar-year corps (or extension Form 7004)
April 15: Q1 2025 estimated tax payment due
April 15: Last day to make IRA/Roth IRA contributions for 2024
April 15: Last day to make SEP-IRA contributions for 2024 (without extension)
April 30: Form 941 (Q1 2025 payroll tax return) due

May 2025:

No major federal deadlines

June 2025:

June 15: Q2 2025 estimated tax payment due

July 2025:

July 31: Form 941 (Q2 2025 payroll tax return) due
July 31: Form 5500 (annual retirement plan report) due for calendar-year plans

September 2025:

September 15: Q3 2025 estimated tax payment due
September 15: Extended S-Corp return (Form 1120-S) due
September 15: Extended partnership return (Form 1065) due

October 2025:

October 15: Extended individual return (Form 1040) due
October 15: Extended C-Corp return (Form 1120) due
October 15: SEP-IRA contribution deadline for extended returns
October 15: Solo 401(k) employer contribution deadline for extended returns
October 31: Form 941 (Q3 2025 payroll tax return) due

December 2025:

December 31: Last day to make charitable contributions for 2025
December 31: Last day to purchase equipment for Section 179 deduction (must be placed in service by December 31)
December 31: Last day to establish and fund a Solo 401(k) for 2025 (the plan must be established by December 31, but employer contributions can be made until the filing deadline)
December 31: Last day to make Roth conversions for 2025

January 2026:

January 15: Q4 2025 estimated tax payment due
January 31: W-2s and 1099-NECs due

What are the penalties for missing these deadlines?

Hypothetical example

Round numbers. A small S-Corp misses three deadlines in 2025.

Missed deadline 1: Form 1120-S (March 15) filed June 1 (2.5 months late).

Late filing penalty: $245/month per shareholder (the amount for returns due in 2025)
1 shareholder x 3 months (fractions of a month count as full months) x $245 = $735
This penalty applies even if the S-Corp owes $0 in tax
If the return is filed within 2.5 months: the penalty is assessed for 3 months

Missed deadline 2: Q2 estimated tax payment (June 15) paid September 15.

Underpayment penalty rate: approximately 8% (annualized, 2025)
On a $5,000 underpayment for 3 months: $5,000 x 8% x 3/12 = $100
Small penalty, but avoidable

Missed deadline 3: Form 941 (Q2, July 31) filed August 20 (20 days late).

Payroll tax deposit was also late (deposited with the late return)
Deposit penalty: 10% of $8,000 deposit = $800 (16+ days late)
Late filing penalty: 5% of $8,000 x 1 month = $400
Total: $1,200

Total penalties from three missed deadlines: $2,035

Two penalties that hit harder than the ones above:

Trust Fund Recovery Penalty (Form 941 withholding). Under IRC 6672, the IRS can assess 100% of unpaid trust fund taxes (employee withholding and the employee share of FICA) personally against the “responsible person,” typically the business owner. This penalty isn’t dischargeable in bankruptcy.
Late 1099/W-2 filing. $60 per form if filed within 30 days of the deadline, $130 if filed by August 1, $330 if filed after August 1 or not filed at all. Maximum penalties vary by business size.

How to avoid:

Set calendar reminders 2 weeks before every deadline
Use a payroll service that auto-files Form 941 and makes deposits
File extensions proactively (an extension costs $0 and avoids the late filing penalty; it doesn’t extend the payment deadline, but the filing penalty is the larger penalty)
Set up EFTPS for estimated tax payments on auto-draft
Hire a CPA or enrolled agent who tracks deadlines for you

The extension strategy: Most CPAs recommend filing Form 7004 for every S-Corp and partnership return, every year, even if the return will be ready by March 15. If something delays the filing (missing documents, K-1s from other partnerships, unexpected issues), the extension is already in place. Filing a return early after an extension costs nothing extra, but a missed deadline without an extension costs $245/month per shareholder for a return due in 2025 ($255 for one due in 2026). The extension gives more time to FILE, not more time to PAY (any estimated tax owed by the shareholder is still due by the original deadline).

Illustrative numbers only, not a real client and not advice for your facts.

What penalties apply for underpaying estimated taxes?

The IRS charges an underpayment penalty under IRC 6654 when you owe more than $1,000 at filing and your withholding and estimated payments are less than the required annual amount. The penalty is calculated separately for each quarter, so a large payment in Q4 doesn’t fully cure an underpayment from Q1 through Q3. You avoid the penalty entirely if your payments cover at least 90% of the current year’s tax or 100% of last year’s tax (110% if your AGI exceeded $150,000). The penalty rate is the federal short-term rate plus 3 percentage points, compounded daily. If your income varies significantly during the year, the annualized income installment method (Form 2210, Schedule AI) can reduce or eliminate the penalty by matching payments to when income was actually earned.

How do I estimate my tax liability for the first year of business?

In your first year, you have no prior-year tax liability to base the safe harbor on, so you must estimate your current-year income. Start with projected gross revenue, subtract estimated deductible expenses, and apply the self-employment tax rate (15.3% on the first $168,600 of net earnings in 2024, 2.9% above that) plus your expected income tax bracket. A conservative approach is to set aside 25-30% of net profit for each quarterly payment. If your income is uncertain, pay a reasonable estimate for Q1 and adjust in Q2 once you have actual numbers. Overpayments are refunded or applied to next year’s estimated taxes.

Related guides:

Small Business Tax Calendar: Every Federal Deadline for Sole Proprietors, S-Corps, and Partnerships

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Cite this page

Yarik Yarosh, CPA. "Small Business Tax Calendar 2025: Every Filing Deadline." Blue Cloud CPA, September 5, 2026, updated October 4, 2026. https://bluecloudcpa.com/guides/small-business-tax-calendar-deadlines-2025

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.