Your Q3 Estimated Taxes Are Due September 15 (Here's How to Pay, and Catch Up If You're Behind)
The third-quarter estimated tax deadline lands on September 15, and it is the one that tends to slip past people. It shows up in the end-of-summer shuffle, after the spring filing rush is a distant memory and before the year-end scramble, so it is easy to forget it is even out there. This is your reminder that it is, plus a walk-through of how to handle it.
If you are not sure what estimated taxes are in the first place, start with my estimated taxes 101 for self-employed providers, which covers the what and the why. This post assumes you already know you owe them and just need to get the Q3 payment done, including if you have fallen behind earlier in the year.
Mark the date: September 15
Your third federal estimated payment for 2026 is due September 15. Despite the "quarterly" label, this one roughly covers what you earned in June, July, and August. New York's third payment is due the same day, so if you owe both, you are making two payments around the same time.
Figure out what to pay
You have two reasonable ways to land on a number, and you do not need to overthink it.
The simplest is the safe-harbor method, which is built to keep you penalty-free. If your payments across the year add up to either 90 percent of what you will owe for 2026 or 100 percent of what you owed last year, you avoid an underpayment penalty even if you still owe a balance in April. (That last-year figure rises to 110 percent if your prior-year income was over 150,000 dollars.) The easy version: take last year's total tax, divide it by four, and that is your quarterly payment. You might still owe more at filing, but no penalty rides along with it.
The other way, which fits if your income is reasonably steady, is to pay a percentage of what you actually earned this quarter. A common starting point is 25 to 30 percent of your gross income, the money you collected before expenses. Remember that as a self-employed person you are covering both income tax and self-employment tax, and self-employment tax alone is 15.3 percent, so the total bite is bigger than people expect. For the full walk-through of the math, the 101 post has it.
Whichever route you take, start from your gross earnings, not from what is left after expenses. Building from the top gives you a cushion, which is exactly what you want with taxes.
How to actually pay it
For the federal payment, the simplest free option is IRS Direct Pay, which pulls straight from your checking or savings account with no fee. If you would rather line up all your payments at once, EFTPS lets you schedule them in advance. You can also pay by card, though the processor charges a fee. Whatever you use, save the confirmation.
For New York, you can pay through your New York State Online Services account at tax.ny.gov, which also pulls from your bank for free, or you can mail Form IT-2105 with a check.
Here is the New York wrinkle that catches people: the state expects estimated payments at a much lower threshold than the IRS does. Federally, you are generally in the estimated-tax system once you expect to owe 1,000 dollars or more for the year. New York wants estimated payments once you expect to owe just 300 dollars or more in state tax. So a fair number of providers who assume they are too small to bother with New York estimates actually do owe them. If you have been paying the IRS but not the state, that is worth a closer look.
If you are already behind
Maybe you missed the April or June payment, or you have not made one all year. Do not let that talk you out of paying now.
The underpayment penalty is not a flat fine. It works like interest charged on the amount you underpaid, calculated quarter by quarter, and it keeps accruing until you pay. That math actually cuts in your favor here: every dollar you pay, even late, even partial, stops the meter running on that dollar. Paying something now is always better than waiting until you can pay it all.
One thing to be clear-eyed about: a big payment now does not fully erase a shortfall from an earlier quarter, because the penalty is figured per period. But it stops the damage from growing and limits what you will owe. That is a real win, not a consolation prize.
Two catch-up tools worth knowing about. First, if you also have a W-2 job, or your spouse does, increasing your paycheck withholding is the most powerful fix available, because the IRS treats withholding as if it were paid evenly across the whole year. A bump in the fall can patch a hole from the spring in a way a late estimated payment cannot. Second, if your income this year was uneven, a slow spring and a busy summer, say, there is a method (the annualized income installment method) that matches your required payments to when you actually earned the money, which can lower or erase the penalty. It is more involved, so it is a good thing to raise with your tax preparer rather than tackle alone.
Make next September easier
If this deadline is stressful, the cause is almost always the same: the money to pay it was not set aside as it came in. The fix is not complicated. Move a percentage of every client payment into a separate tax savings account the moment you get paid, and by the time September rolls around, the payment is already sitting there. That one habit turns the quarterly deadline from a scramble into a transfer. I wrote about building bookkeeping habits that actually stick if you want a place to start.
The bottom line
September 15 is coming. Calculate your number using last year's tax or a percentage of what you have earned, pay both the IRS and New York if you owe them, and keep your confirmations. If you are behind, pay what you can now rather than waiting, because the penalty only grows the longer it sits. None of this has to be perfect to keep you out of trouble. It just has to get done.
This is general information, not tax advice for your situation. If your numbers are complicated or you are not sure where you stand, a tax preparer who works with self-employed clients can sort it out quickly. My Guide to Estimated Taxes also breaks the process down step by step if you want a reference to keep.
And if you would rather not track any of this yourself, book a free call with me and we can talk through a setup that keeps your tax money sorted all year.