Q4 Estimated Tax Is Due January 15, 2027 — Here's What to Pay

The weird thing about my Q4 estimated tax is that the deadline is January 15, 2027, not December 31. My fourth quarter estimated tax 2026 calculation covers income from September 1 through December 31, yet I pay it about two weeks into the next calendar year. I have watched otherwise organized people label that payment “2027” because the bank transfer happened in January. I write “2026 Form 1040-ES” beside the amount before I open the payment site.

A large December project belongs in that calculation when I receive the income in 2026. Last year, a final project payment of $12,740 landed on December 29 after I had mentally closed the books. It pushed up both my income-tax estimate and self-employment tax. Ignoring it until filing would not make it a January problem; it would leave the January 15 estimated tax payment short.

I start with actual 2026 profit, not deposits. I add paid invoices through December 31, subtract ordinary business expenses, include other household income and withholding, and subtract every estimated payment already made. Then I run the updated numbers through the tax calculator. If my annual federal target is $18,936.44 and I have already paid $13,204.20, my remaining planning amount is $5,732.24. I calculate state tax separately because an IRS payment does nothing for my state account.

If I have used prior-year safe harbor all year, Q4 is less dramatic. I take the applicable annual target, usually 100% of prior-year total tax or 110% when the prior-year AGI rule applies, subtract the timely payments and withholding already credited, and pay the remaining installment. I still save for any larger current-year balance. Safe harbor can protect me from an underpayment penalty; it does not discount a profitable year.

If I missed Q1 or Q2, I do not tell myself one giant quarterly tax payment January deposit will travel backward in time. It will not. An earlier installment can still have a penalty for the days it was underpaid. Paying the shortfall with Q4 can stop more days from accumulating and reduce the annual penalty, so catching up still matters. I keep the payment date because timing, not just the annual total, is part of the calculation.

I also compare the payment with my September-through-December records instead of calling every dollar that arrived after Labor Day “Q4 profit.” I may collect a September invoice for August work, and cash-basis timing can put that receipt in the later payment period. I keep the deposit date beside the invoice date so I can explain what I used. That two-column note looks primitive, but it has settled more questions than my elaborate forecast tab.

I have one escape hatch, although it requires me to become the sort of person who finishes a tax return almost immediately. The 2026 Form 1040-ES instructions say I can skip the January 15 payment if I file my 2026 return by February 1, 2027 and pay the entire balance with it. The date is February 1, not February 2. I would use that option after an unusually big December only if my bookkeeping, forms, and cash were ready; buying 17 days is not useful if a 1099 is still missing.

For the payment itself, I use IRS Direct Pay at directpay.irs.gov. It usually takes me about five minutes when I have a prior-year return, routing number, account number, payment amount, and tax year ready. The session warning offers another 15 minutes, and the page can expire while I hunt for an old address or AGI. Nothing improves a tax evening like entering bank details twice.

I gather the numbers first.

I select “Estimated Tax,” Form 1040-ES, and tax year 2026. I check the year again before submitting because January makes 2027 look reasonable on the screen. Then I save the confirmation number, amount, scheduled date, and bank account used. My longer IRS Direct Pay walkthrough covers the clicks and the identity-verification annoyances.

The Q4 deadline is my last payment checkpoint, not my first look at the year. I close December books as soon as the final bank activity posts, calculate the gap, and schedule the transfer several days before January 15. Six weeks sounds generous in November. It feels much shorter after New Year's Day.