Fourth-quarter estimated tax 2026: what to pay by January 15, 2027

The last estimated tax payment for 2026 is due Friday, January 15, 2027. How much must be in by then is set by the safe harbor in section 6654 of the Internal Revenue Code: withholding plus the four timely installments must reach the smaller of 90% of your 2026 tax or 100% of the tax on your 2025 return, 110% of it if your 2025 adjusted gross income was over $150,000 ($75,000 if married filing separately). Owe less than $1,000 after withholding and no installments are required. A single filer with $145,000 of wages ($4,350 deferred to a 401(k)) and $30,000 of side profit who paid the first three installments sends $1,596 on January 15 and settles the remaining $3,208 at filing, with no penalty. An installment left unpaid costs 7% a year, by the day, until it is paid.

The numbers

Every figure below comes from the MoneyVibe quarterly estimated tax calculator: 2026 brackets and standard deduction, self-employment tax with the 20% qualified business income deduction, the section 6654 safe harbor, four equal installments, and the Form 2210 penalty method at the 2026 IRS rates (7%, 6%, 7% and 7% by quarter). The calculator does not accept capital gains, so the two gain rows use the federal tax engine behind the tax bracket calculator plus the same safe harbor arithmetic. Withholding is assumed to equal the tax on the wages alone. Results are rounded to the nearest dollar.

W-2 plus side income. $145,000 of wages with $4,350 deferred to a 401(k), $30,000 of self-employment profit, single. The year's tax is $32,082 ($27,843 of income tax, $4,239 of self-employment tax); withholding covers $22,490, so $9,592 is still owed, over $1,000. With no 2025 figures entered, the target is 90% of this year's tax, $28,874, so $6,384 of estimated payments are needed, $1,596 on each date. On plan, January 15 takes $1,596 and the last $3,208 goes with the return by April 15, 2027, penalty-free.

If none of the first three installments was paid, January 15 calls for $6,384 (the $4,788 shortfall plus that date's $1,596). Paying it then clears the fourth date but not the first three: each missed installment is charged from its due date to the day it is paid, $183 for the three together, or $293 if all four wait until April 15, 2027. A single $1,596 January installment left to April 15 costs $28.

Self-employed, last year's tax known. $120,000 of profit, no wages, single, and a 2025 return showing $20,000 of tax on $110,000 of adjusted gross income. The 2026 tax is $28,462 ($16,955 of it self-employment tax), so 90% would be $25,616. But 100% of last year's tax, $20,000, is smaller, and the smaller target governs: $5,000 a quarter, $5,000 on January 15, and the remaining $8,462 at filing with no penalty.

A large gain in the fourth quarter. A couple filing jointly with $170,000 of wages ($10,000 deferred to a 401(k)) sells stock in November for a $60,000 long-term gain. Federal tax rises from $17,540 to $26,540, the whole gain taxed at 15%. Whether anything is due January 15 turns on 2025. If that return showed $15,500 of tax on $140,000 of income, withholding of $17,540 already exceeds 100% of it: no estimated payment is required and the $9,000 of extra tax is paid with the return. If 2025 was a higher year, $25,000 of tax on $165,000 of income, the 110% target is $27,500, more than 90% of this year's tax, $23,886, so the 90% rule applies and $6,346 is due by January 15. Because the gain arrived in the fourth period, Schedule AI of Form 2210 (the annualized income installment method) puts the entire $6,346 in the January 15 column. Without it the IRS would spread the amount $1,587 per date and charge $182 on the three "late" ones even if all is paid on January 15.

Why it works this way

Section 6654(d)(1) defines the required annual payment as the lesser of 90% of the tax shown on the current year's return and 100% of the tax on the preceding year's return; section 6654(d)(1)(C) substitutes 110% when the preceding year's adjusted gross income exceeded $150,000, or $75,000 for a married person filing separately. The prior-year route needs a 12-month prior year with a return filed. Each installment is 25% of the annual payment, due April 15, June 15, September 15 and January 15 (section 6654(c)). Section 6654(e)(1) removes the addition to tax when the year's tax less withholding is under $1,000; Publication 505 (2026) and Form 1040-ES state the same General Rule.

The penalty is interest in all but name: Form 2210, Part III, charges each underpaid installment the underpayment rate for the days from its due date to the date paid, or to April 15, 2027, over 365, figured separately for each due date, so paying enough later does not erase a missed earlier date (Instructions for Form 2210, 2025 version; the 2026 version was not yet published). Revenue Ruling 2026-15, in Internal Revenue Bulletin 2026-36, sets the rate at 7% for the quarter beginning October 1, 2026, after 7%, 6% and 7% earlier in the year. The rate for January to March 2027 had not been announced on October 10, 2026; the calculator assumes 7%.

Withholding is treated differently from an estimated payment, which most employees overlook. Under section 6654(g), tax withheld from wages is deemed paid in equal parts on the four due dates, whatever month it was actually withheld, unless you elect to use the real dates (Form 2210 instructions: one-fourth on each date unless you show otherwise). An estimated payment counts only on the day it is made.

For uneven income, section 6654(d)(2) allows the annualized income installment. Schedule AI of Form 2210, and Worksheet 2-9 in Publication 505, annualize the income earned through March 31, May 31, August 31 and December 31 (multiplying by 4, 2.4, 1.5 and 1), take 22.5%, 45%, 67.5% and 90% of the tax on each figure, and subtract the installments already required. A November gain appears only in the final column, so the $6,346 above is owed in one piece on January 15 rather than counted late for the earlier dates. Form 1040-ES names a large capital gain late in the year as a case for it.

Filing the 2026 return and paying the full balance by the end of January also satisfies the January installment: Publication 505 says January 31, 2027, and Form 1040-ES gives February 1 because January 31 is a Sunday.

What changes the answer

• Last year's tax. The prior-year target is known on January 1 and cannot be missed by a good year; it cuts the self-employed filer's required payments from $25,616 to $20,000 and removes the January payment for the couple whose 2025 tax was $15,500. Use line 24 of the 2025 Form 1040; line 11b decides the 110% test.
• Extra withholding before December 31. The single filer who paid nothing could instead have $6,384 more withheld from the pay left in 2026, $1,596 from each of four remaining paychecks through Form W-4 Step 4(c). Deemed paid evenly across the four dates, that withholding leaves $0 of estimated tax needed and no penalty, where the same $6,384 sent on January 15 still leaves $183 owed for the first three dates.
• When the income arrived. Lumpy income looks late under the regular method and on time under Schedule AI; skipping it costs $182 in the gain example.
• Owing under $1,000 after withholding. With $2,000 of side profit instead of $30,000, the single filer would owe $639 after withholding and need no installment.

What to do first

1. Pull three figures: 2026 federal tax withheld to date from your latest pay stub, the total tax (line 24) and adjusted gross income (line 11b) from your 2025 return, and the estimated payments already made in 2026, plus any income with no tax withheld.
2. Enter them in the quarterly estimated tax calculator with "After September 15" selected. It shows which target governs, the January 15 payment including any catch-up, and what leaving it unpaid until April 15 would cost; profit after expenses can be checked first in the side hustle tax calculator.
3. If you are behind with paychecks left in 2026, compare a new Form W-4 with the shortfall in Step 4(c), which counts as paid evenly through the year, against an estimated payment on January 15, which stops the charge only from that day. If a gain or bonus came late in the year, plan to attach Form 2210 with Schedule AI.

What this does not model

The calculator takes wages, a 401(k) deferral and self-employment profit, not capital gains, dividends, interest, rent, retirement distributions or Roth conversions; the two gain rows came from the federal tax engine with the safe harbor applied as section 6654 states it. Not modelled here: the 3.8% net investment income tax and the 0.9% Additional Medicare tax (both count as tax for the safe harbor; the gain example stays under their $250,000 joint threshold), credits, state estimated taxes, married filing separately, farmers and fishers, the 2027 rate, and the Topic 306 waivers for casualty, disaster, retirement after 62 or disability.

Next steps: run your own figures in the quarterly estimated tax calculator, read the library chapter withholding and quarterly taxes, or see the glossary entries for the estimated tax safe harbor and estimated tax payments.

Not tax or legal advice. Federal rules as published by the IRS in Publication 505 (2026), Form 1040-ES (2026), the Instructions for Form 2210 and Revenue Ruling 2026-15, read on October 10, 2026; confirm with a tax professional before acting.