The 2026 Small Business Tax Calendar: Every Deadline, Form, and Penalty

Owner-operators lose more money to missed deadlines than to anything else in the tax code. Not because the penalties are enormous on day one, but because they compound. A $485 late-filing penalty on an 1120S becomes $2,425 by month six. A missed quarterly estimate becomes an underpayment penalty that quietly eats your spring refund.

This is the full 2026 calendar. Save it, pin it, or just subscribe to our deadline reminders — we send one 14 days out and one 3 days out for every date that applies to your entity.

Q1 — the loud quarter

January 31

• Form W-2 / W-3 — distribute to employees and file with SSA. $60 per form if up to 30 days late, climbing to $630/form past August 1.
• Form 1099-NEC — issue to every contractor you paid $600 or more. Same penalty ladder as W-2.
• Form 1099-MISC — rents, awards, legal fees. February 28 for paper, March 31 for e-file, but issue to recipients by January 31.
• Form 941 Q4 — payroll tax return for October–December. 5% per month of unpaid tax, up to 25%.
• Form 940 — annual federal unemployment tax. Same ladder.

March 15

• Form 1120S (S-corporations) — due. Extension via Form 7004 pushes to September 15. Late-filing penalty: $220 × number of shareholders × months late, up to 12 months.
• Form 1065 (Partnerships) — same date, same penalty structure. $220 × partners × months.

Note: 1120S and 1065 are information returns, so the IRS does not technically owe them money — but they still fine you if you file late.

Q2 — the quiet killer

April 15

• Form 1040 — individual federal return. Extension via Form 4868 pushes to October 15.
• Form 1120 (C-corporations) — same date for calendar-year filers.
• Q1 estimated tax — personal and corporate. This is where owner-operators get hurt: you took distributions in Q1 and now owe a quarterly estimate on them.
• FBAR (FinCEN 114) — foreign bank account reporting. Automatic extension to October 15 but file.

April 30

• Form 941 Q1 — payroll tax return.

June 15

• Q2 estimated tax — six weeks after Q1 is due. Easy to miss because April just drained you.

Q3 — the extension cliff

July 31

• Form 941 Q2 — payroll tax.

September 15

• 1120S extended returns — if you filed 7004 in March. If you miss this one, the penalty ladder resumes.
• Form 1065 extended returns — same.
• Q3 estimated tax — personal and corporate.

October 15

• 1040 extended — if you filed 4868 in April.
• 1120 extended — if you filed 7004 in April.
• FBAR extended — if you missed the April deadline.

Q4 — plan ahead

October 31

• Form 941 Q3 — payroll tax.

December 31

• Last day for business deductions to count toward this tax year. Equipment purchases, retirement contributions, Section 179 elections.
• Required Minimum Distributions for retirement accounts if applicable.

January 15 (of the following year)

• Q4 estimated tax — for the year that just ended.

State deadlines

Every state is different. Illinois follows the federal calendar for IL-1120, IL-1040, and quarterly estimates. California has franchise tax due March 15 for S-corps regardless of income. New York requires MCTMT quarterly. Texas has no personal income tax but franchise tax is May 15. We track yours as part of your plan and send reminders.

Payroll-specific calendar

If you have employees, there is a parallel calendar you should also know:

• Semi-weekly depositors: next-business-day deposits for payroll taxes exceeding $100k on any day, Wednesday-after-Wednesday-payday or Friday-after-Saturday-payday otherwise.
• Monthly depositors: 15th of the following month.
• Form 941: quarterly (Jan 31 / Apr 30 / Jul 31 / Oct 31) — reconciles what you deposited.
• Form 940: annual (Jan 31) — FUTA.

Missing a payroll deposit triggers a different penalty structure that stacks fast: 2% if 1–5 days late, 5% if 6–15 days, 10% past 15 days, 15% past the first IRS notice. On a $4,000 quarterly deposit that is $600 by day 16.

What a good system looks like

• Every deadline that applies to your entity in one calendar.
• Automatic reminders 14 and 3 days out.
• A real human preparing the actual return, not a web form.
• Documentation retained for 7 years (the IRS statute of limitations).

That is what we built into Foxel's deadline engine. If you are reading this because you missed something, we can usually file an abatement request — the IRS waives most first-time penalties if you ask correctly. Talk to a Foxel advisor and bring a copy of the notice.