Updated November 4, 2026. Quick answer: Worksheet 2-12 in Publication 505 (2026) is the IRS seven-line calculation for the payments still due after you refigure your estimated tax during the year. It multiplies the amended total by the share that should be paid by the next due date, subtracts what you already paid, and spreads the rest over the later dates.
What the worksheet is for
The publication states the trigger: “If you refigure your estimated tax during the year or if your first estimated tax payment is due after April 15, 2026, figure your required payment for each remaining payment period using Worksheet 2-12.” Form 1040-ES points here too: “To change or amend your estimated tax payments, refigure your total estimated tax payments due (see the 2026 Estimated Tax Worksheet).” The first step is therefore the 2026 Estimated Tax Worksheet, which gives line 1 of this sheet.
The seven lines
| Line | What it asks |
|---|---|
| 1 | “Amended total estimated tax due” |
| 2 | “Multiply line 1 by:” “50% (0.50) if next payment is due June 15, 2026”; “75% (0.75) if next payment is due September 15, 2026”; “100% (1.00) if next payment is due January 15, 2027” |
| 3 | “Estimated tax payments for all previous periods” |
| 4 | “Next required payment: Subtract line 3 from line 2 and enter the result (but not less than zero) here and on your payment voucher for your next required payment” |
| 5 | “Add lines 3 and 4” |
| 6 | “Subtract line 5 from line 1 and enter the result (but not less than zero)” |
| 7 | “Each following required payment: If the payment on line 4 is due June 15, 2026, enter one-half of the amount on line 6 here and on the payment vouchers for your payments due September 15, 2026, and January 15, 2027.” “If the amount on line 4 is due September 15, 2026, enter the amount from line 6 here and on the payment voucher for your payment due January 15, 2027” |
The sheet also carries a stop rule: “Note: If the payment on line 4 is due January 15, 2027, stop here. Otherwise, go to line 5.” In that case line 4 is the last payment and lines 5 to 7 do not apply.
The IRS example, recomputed
The publication gives its own case: “Early in 2026, you figure estimated tax due of $1,800.” “You make estimated tax payments on April 15 and June 15 of $450 each ($1,800 ÷ 4).” “On July 10, you sell investment property at a gain.” “Your refigured estimated tax is $4,100.” It states the results: “The required estimated tax payment for the third payment period is $2,175.” “If your estimated tax does not change again, the required estimated tax payment for the fourth payment period will be $1,025.” Running those numbers through the seven lines gives the same two payments, as the table shows.
| Line | Entry | Amount |
|---|---|---|
| 1 | Amended total estimated tax due | $4,100 |
| 2 | Line 1 times 0.75, next payment due September 15 (computed) | $3,075 (computed) |
| 3 | Estimated tax payments for all previous periods ($450 plus $450) | $900 |
| 4 | Line 2 minus line 3 (computed): next required payment | $2,175 (computed) |
| 5 | Lines 3 and 4 added (computed) | $3,075 (computed) |
| 6 | Line 1 minus line 5 (computed) | $1,025 (computed) |
| 7 | Each following required payment, due January 15, 2027 | $1,025 |
Line 2 is computed as $4,100 times 0.75, which is $3,075. Taking away the $900 already paid leaves $2,175 for September 15. Line 6 is computed as $4,100 minus $3,075. That leaves $1,025 for January 15, 2027.
A second case with invented numbers
Illustration, not an IRS example. Estimated tax is refigured to $6,000 before the June 15 payment, and only the April payment of $1,500 has been made.
| Line | Entry | Amount |
|---|---|---|
| 1 | Amended total estimated tax due (invented) | $6,000 |
| 2 | Line 1 times 0.50, next payment due June 15 (computed) | $3,000 (computed) |
| 3 | Estimated tax payments for all previous periods (invented, April only) | $1,500 |
| 4 | Line 2 minus line 3 (computed): next required payment, June 15 | $1,500 (computed) |
| 5 | Lines 3 and 4 added (computed) | $3,000 (computed) |
| 6 | Line 1 minus line 5 (computed) | $3,000 (computed) |
| 7 | One half of line 6 (computed): each of the September 15 and January 15 payments | $1,500 (computed) |
The June 15 payment is $1,500, which brings the total paid to $3,000, half of the amended total. The remaining $3,000 is split into two payments of $1,500, due September 15 and January 15, 2027.
Why the earlier payments matter
The worksheet does not rewrite periods that have already passed. The publication warns: “The penalty is figured separately for each payment period.” Form 1040-ES adds the consequence: “If an estimated tax payment for a previous period is less than one-fourth of your amended estimated tax, you may owe a penalty when you file your return.” When income arrived unevenly, the annualized method on Schedule AI is the way to reduce that penalty.
Edition
This page reads Publication 505 (2026), Tax Withholding and Estimated Tax, the file irs.gov served on 2026-11-04 (sha256 in the kit data). Line numbers and letters belong to that edition, so check the label printed on the worksheet in your own copy before you follow a line reference. The dates in the worksheet are the 2026 estimated tax dates printed in that edition.
Common mistakes
- Using the 25% quarter shortcut after a mid-year change. This sheet uses 50%, 75% or 100% of the amended total depending on the next due date.
- Forgetting to subtract every earlier payment, including a 2025 overpayment you applied to an installment.
- Continuing past line 4 when the next payment is the January 15, 2027 one. The sheet says to stop there.
- Assuming a late increase wipes out a penalty for earlier periods. The penalty is figured period by period.
Related: 2026 Estimated Tax Worksheet, Schedule AI, and estimated tax due dates.
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Answer againSources
- Publication 505 (2026), Tax Withholding and Estimated Tax: https://www.irs.gov/pub/irs-pdf/p505.pdf
- Form 1040-ES (2026), Estimated Tax for Individuals: https://www.irs.gov/pub/irs-pdf/f1040es.pdf
Read from the IRS documents linked above on November 4, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.