Every 2026 deadline that matters
When a federal deadline falls on a Saturday, Sunday, or legal holiday, it rolls to the next business day. Two of 2026's do. We have flagged them so you are not working to the wrong date.
| Date | What is due | Who it applies to |
|---|---|---|
| Jan 15 | Fourth-quarter 2025 estimated tax payment | Anyone paying quarterly estimates |
| Jan 31 Falls on a Saturday — observed Mon, Feb 2 |
W-2s and 1099-NECs furnished to recipients and filed | Every employer and payer |
| Mar 15 Falls on a Sunday — observed Mon, Mar 16 |
Partnership (1065) and S-corporation (1120-S) returns, or extensions | Partnerships, LLCs taxed as partnerships, S-corps |
| Apr 15 | Individual returns (1040), C-corporation returns (1120), Q1 estimated payment, and the last day to fund an IRA or HSA for 2025 | Individuals, C-corps, quarterly filers |
| Jun 15 | Second-quarter estimated tax payment | Quarterly filers |
| Sep 15 | Third-quarter estimate, plus extended partnership and S-corp returns | Quarterly filers; extended pass-throughs |
| Oct 15 | Extended individual returns (1040) | Anyone who filed an extension in April |
| Dec 31 | Last day for most planning moves to count for 2026 | Everyone — see the note below |
State deadlines can differ from federal, and Illinois is not always the same as the state you earned the income in. If you file in more than one state, treat this calendar as the floor, not the whole picture.
When to call us — and what for
The expensive tax mistakes almost never happen at filing time. They happen months earlier, when a decision gets made without anyone asking what it does to your taxes. If any of these is on your horizon, that is the moment to reach out.
You’re starting or buying a business
Entity choice — LLC, S-corp, C-corp — shapes your taxes for years. Get it right before the formation is filed, not after.
You’re selling a business or practice
The tax on a sale is largely set by moves made 6–18 months ahead. Call while it’s a plan, not a signed letter of intent.
A liquidity event is coming
An IPO, RSU vesting, or a large stock sale — timing and structure can move the bill by six figures.
Your income jumped
A big bonus, a promotion, a windfall year. Estimated payments and bracket timing need to change now, not in April.
You’re buying or selling real estate
Cost segregation, 1031 exchanges, and basis planning all have to be set up before the closing.
Something changed at home
Marriage, divorce, a new child, or a death in the family each change filing status, dependents, or estate exposure.
You received an inheritance or large gift
Basis, step-up, and gift and estate coordination are easy to get wrong and expensive to unwind later.
You’re earning in more than one state
Multi-state and residency questions are where we see the most avoidable penalties.
A notice arrived from the IRS or your state
Don’t sit on it. Most are routine, but the clock starts the day it’s dated — a fast, correct response is everything.
December 31 is a real wall
Most of what actually lowers a tax bill has to happen before the year closes — entity elections, retirement plan design, cost segregation, timing income and deductions. April is when the return gets filed; by then the result is already set. This is the single most expensive misunderstanding we see, and it is why we run planning in the autumn rather than the spring.
How long to actually keep it
The honest answer is that it depends on what the document proves — not on the calendar. The clock usually runs from the date you filed.
The normal case
Returns and the records behind them — W-2s, 1099s, receipts, mileage logs, charitable acknowledgements. This matches the usual window the IRS has to assess additional tax.
If income was understated
Where more than 25% of gross income was omitted, the assessment window doubles. If your income is complex or K-1 heavy, six years is the safer default.
Worthless securities & bad debt
Claims for a loss from worthless securities or a bad-debt deduction carry a longer window. Keep the documentation that establishes basis and worthlessness.
While you still own it — plus 3
Property, improvement and depreciation records establish basis. Keep them for as long as you hold the asset, then for the normal period after you sell it.
The permanent file
Returns themselves, entity formation documents, elections (S-corp, PTET), retirement plan documents, estate and trust instruments. These cost nothing to store and are painful to reconstruct.
Employment tax records
Payroll records run on their own clock — four years after the tax is due or paid, whichever is later.
If a return was never filed, or was filed fraudulently, there is no time limit at all — keep everything.
What clients ask us
Does an extension give me more time to pay?
No — and this catches people every year. An extension moves the filing deadline, not the payment deadline. Tax owed is still due in April; interest and penalties accrue from that date. File the extension, but pay your best estimate with it.
Can I keep everything digitally?
Yes. Electronic copies are acceptable provided they are complete, legible, and you can produce them on request. In practice we recommend one indexed archive with an off-site backup — a shoebox of fading thermal receipts is worse than a folder of scans.
I file in several states. Does this calendar still apply?
The federal dates do. State dates often do not — some states set their own deadlines, and pass-through entity tax elections in particular have their own timing. Multi-state is where we see the most avoidable penalties, and it is worth a conversation rather than a table.
Is it too late to do anything about last year?
Sometimes not. Amended returns are available for a limited period, and there are situations — missed elections, unclaimed credits, cost segregation on property you already own — where prior years can still be reached. It is worth asking before assuming the door is closed.