Sold crypto this year? The IRS expects its cut on September 15 — not next April.
The third estimated-tax installment for the 2026 tax year is due Tuesday, 15 September 2026. If you realized gains in June or July and nothing has been withheld against them, part of that tax was already due in June and the rest is due now. Miss it and the shortfall accrues interest at 7% until you file.
Most guides stop at "pay 90% of what you'll owe", which frightens people into overpaying. The rule is kinder than that: the safe harbour is the lesser of two tests, and one of them is simply last year's tax. Work out which one applies to you below.
What this is. The section 6654 safe-harbour arithmetic, run on figures you type, with every rule cited. Nothing is uploaded and nothing is stored — the calculation happens on our server and the answer is not written anywhere. It is information, not advice, and it covers federal estimated tax only. ClearBasis is tax software — not a law firm, accounting firm or tax preparer.
The three deadlines that have already passed, and the one that hasn't
Each installment is a quarter of your required annual payment, so by 15 September three quarters of it should be in. Tax withheld from a salary counts as paid evenly across the year under §6654(g), whichever month it was actually withheld — which is why a lot of people who assume they are behind are not.
Your figures
We never guess a tax bracket. Your rates are yours — they depend on your total income, your filing status and your state, and we know none of those.
Every line above is arithmetic on what you typed. Change a figure and re-run — nothing is remembered between runs.
The third 2026 installment. Pay it directly to the IRS — we never touch your money and never ask for a bank detail.
- IRS Direct Pay — bank transfer, no account needed. Choose Estimated Tax, reason 1040ES, tax year 2026.
- EFTPS — if you already have an account, same selection.
- Form 1040-ES voucher 3 — if you post a cheque. Write your SSN and "2026 Form 1040-ES" on it.
Paying part of it still helps: this penalty is interest on the shortfall, not a flat fine, so it stops accruing on whatever you send the day you send it. Late is cheaper than never — which is the opposite of how most penalties behave.
What this does not cover
Your state
Most states with an income tax run their own estimated-tax schedule, usually on the same dates, occasionally not, and with their own penalty rate. This calculation is federal only.
A lumpy year
If your gains all landed in one quarter, the annualized income installment method (Form 2210, Schedule AI) matches each installment to when the income actually arrived, and can erase a penalty that the flat quarterly assumption above shows. More paperwork; the right answer for an uneven year.
Unrealized positions
Holding is not a taxable event. Only what you sold, swapped, spent or received as income belongs in the figures above — a coin that has doubled and stayed in your wallet owes nothing yet.
Whether the gain is right
Garbage in, garbage out: if the gain you typed came from a 1099-DA with blank cost basis, it is almost certainly overstated. The free scan rebuilds the basis before you pay tax on money you never made.
Questions people actually ask
I already paid nothing all year. How bad is it?
Usually much less than people fear. The penalty is interest at 7% on the shortfall, running from each missed due date — on a $5,000 shortfall from 15 September to the April filing date that is roughly $200, not a percentage of your whole tax bill. And if last year's tax was small, the safe harbour is small, so the shortfall may be smaller than you think.
Can I just pay it all in January instead?
You can, and it is far better than not paying — but interest accrues from each installment's own due date, so the September shortfall keeps running until the money arrives. Paying in September costs four months less than paying in January.
My employer withholds tax. Does that count?
Yes, and generously: §6654(g) treats withholding as paid evenly across the year regardless of when it happened. Someone who increases their withholding in November still gets credit as though a quarter of it had been paid by each due date. That is the one lever that works retroactively.
What if I overpay?
It comes back as a refund when you file, without interest for you. That is the real cost of the "just pay 90%" advice — money parked with the Treasury for seven months when the prior-year safe harbour would have let you keep it.
Does the exchange withhold anything for me?
Not today. A 1099-DA reports proceeds; it does not withhold tax. Backup withholding on digital-asset sales is a separate rule arriving for some accounts from 2027 — worth knowing about, but it does not help you this September. What your 1099-DA actually says →
Is this advice?
No. It is the statutory arithmetic run on figures you supplied, with the sections cited so you or your accountant can check it. Whether to pay, and how much, is your decision.
Tell me before the next one
The fourth 2026 installment is due 15 January 2027, and the same question comes back every quarter. Save a free scan and we will work the number out again from your own ledger before each deadline — deadline-driven only, nothing else, ever.
Saved. Reminders start when email delivery activates — the permanent record is your scan, not your inbox.
Sources: IRC §6654(d)(1)(B)–(C), (e)(1)–(2), (g) · IRS Estimated taxes FAQ (due dates, the $150,000/$75,000 threshold, the $1,000 de-minimis) · Rev. Rul. 2026-10, IRB 2026-22 (7% underpayment rate, quarter beginning 1 July 2026). Retrieved 27 August 2026.