It's that time again: your next quarterly tax installment is due April 15*, which is three weeks from now. Yes, this also when your personal tax return balance due is due: it feels rude. If you don’t already know how much you’re going to pay in, now is the time to block out some time on your calendar to get that sorted out.

Want a tangible reminder of estimated tax deadlines along with these emails? Reply with your snail mail address and I’ll pop one of these schmancy locally made letterpress coasters in the mail for you. Offer good until I run out of coasters or forever stamps. (It will take me 45 more years to use these all up myself, please help.)

To avoid tax underpayment penalties and interest on your individual federal taxes, you need to pay in enough between withholding and estimated taxes equal to the smaller or 90% of your current year (2026) taxes or 100% of your prior year (2025) taxes. (If you’re a high earner, that jumps to 110% of your prior year taxes.) 

Tax pros typically provide you ‘safe harbor’ estimated tax vouchers, which incorporate the following assumptions: (1) any withholding you had in 2025 will be exactly the same in 2026 and (2) you want to pay in enough estimated taxes to pass the prior year percent test for avoiding underpayment penalties and interest.

If your 2026 is going to be largely different than your 2025 on the withholding front or there are other year over year differences, you can ask your tax pro to help you fine tune how much to pay in! Be persistent about following up with your tax pro, they’re in mile 20 of their tax season marathon and real tired at this point. You might need to nudge them more than once.

Back in two weeks to remind you again,
Kat

*CPA Nag treats all deadlines that occur on the 15th or the following Washington DC business day as if they fall on the 15th. The added complexity of keeping track of weekends and holidays is not, in our opinion, worth spending your energy on.