Q2 estimated taxes 2026: what to actually send by June 15
If your year is up over last, your safe-harbor number is wrong. A two-step adjustment that takes ten minutes and dodges April penalties.
Two-thirds of the small-business owners we onboard pay their quarterly estimates on autopilot — the same number, every quarter, set by last year’s CPA before the world changed. That works when your income is flat. It doesn’t when it isn’t.
If your trailing twelve months are 25% above last year’s full-year revenue, your June 15 voucher needs to move. Here is the ten-minute version.
Two safe harbors, pick the cheaper
The IRS won’t charge underpayment penalties if you pre-pay either 90% of this year’s eventual tax or 100% of last year’s tax (110% if your prior-year AGI was over $150,000). You pay quarterly, in roughly equal installments, and you only have to hit one of the two.
The trap is the “100% of last year” path. It is the easy one — same number, four times a year — but it leaves you exposed in April for the additional tax owed on the higher income. The penalty is gone, but the cash bill isn’t.
The safe harbor saves you from penalties, not from the actual tax. Plan for both.
The two-step adjustment
Step one: pull your trailing-12-month gross income and net profit from your books. (If your books are not closed through April, this is your sign.)
Step two: apply your effective federal rate from last year’s return to the increase in net profit. Add 7.65% if you are self-employed and crossed the Social Security wage base this year. Divide by 4. That is the additional amount to add to each remaining quarterly voucher.
A small example. Last year’s tax was $24,000, paid as $6,000 quarterly. This year’s profit is tracking 30% higher. Effective rate last year was 22%. Additional quarterly voucher: ($6,000 × 0.30) ≈ $1,800. New Q2 voucher: $7,800.
You will overpay slightly. That is the point. The federal underpayment rate is 8% this year, and the cash you didn’t send sits in your operating account doing nothing useful at scale.
State estimates are not optional
Most states have their own safe harbors, their own forms, and their own underpayment rules. Some — California, New York, New Jersey — are more aggressive than the IRS about chasing them. Whatever you add to the federal voucher, add the corresponding state piece in the same envelope.
If your business operates across multiple states, the apportionment gets ugly fast. That is a separate post.
What we tell clients
We re-run estimated taxes for every client every quarter, fifteen days before the voucher is due, and send a one-page memo with the recommended number. It is not glamorous, and it is the single highest-ROI thing we do for any business growing faster than 15% year-over-year. If you would like that done for your business, book a call and bring last year’s return.
