Updated October 18, 2026. Quick answer: Lines 18 to 23 are the Refund or Amount You Owe section of Form 1040-X. Line 18 is any overpayment already shown on the original return, line 19 subtracts it from total payments, and then either line 20 shows what you owe or line 21 shows the overpayment, which lines 22 and 23 split between a refund and next year’s estimated tax.
Read box by box from the IRS form text: Form W-2c Notice to Employee.
Related reading on this site: IRS Notice CP12 (refund created or changed), IRS Notice CP53A (direct deposit rejected by the bank), IRS Notice CP53D (paper check instead of requested direct deposit) and IRS Notice CP53E (add or update a bank account).
How the section works
The instructions open with “The purpose of this section is to figure the additional tax you owe or excess amount you have paid (overpayment).” They explain the method: “It is as if you were using the new information to complete your original return.” “If the results show a larger overpayment than before, the difference between the two becomes your new overpayment.” “You can choose to receive the refund or apply it to your estimated tax for the following year.”
Line 18: overpayment from the original return
The form’s caption is “Overpayment, if any, as shown on original return or as previously adjusted by the IRS”. The instructions say “Enter the overpayment from your original return.” “Don’t include interest you received on any refund.” They add “Any additional refund you are entitled to on Form 1040-X will be sent separately from any refund you haven’t yet received from your original return.”
Line 19: the subtraction
The caption is “Subtract line 18 from line 17. (If less than zero, see instructions.)”. The instructions explain the negative case: “If line 18 is larger than line 17, line 19 will be negative.” “You will owe additional tax.” “To figure the amount owed, treat the amount on line 19 as positive and add it to the amount on line 11. Enter the result on line 20.” Line 17 is on the lines 12 to 17 page.
Computed illustration, not an IRS example: if line 17 is $5,400 and line 18 is $1,000 then line 19 is $5,400 minus $1,000 and that is $4,400.
Lines 20 and 21: amount you owe or amount overpaid
Line 20 reads “Amount you owe. If line 11, column C, is more than line 19, enter the difference.” Line 21 reads “If line 11, column C, is less than line 19, enter the difference. This is the amount overpaid on this return”. The instructions for line 20 say “The IRS recommends paying the amount due on line 20 electronically whenever possible.” and “If you file Form 1040-X electronically, you can simultaneously authorize the Treasury to make an electronic withdrawal (direct debit) for the balance due.” The instructions have no separate paragraph for line 21. The matching line on the original return is on the Form 1040 line 37 page.
Lines 22 and 23: refund or estimated tax
Line 22 is captioned “Amount of line 21 you want refunded to you”. The instructions say “The refund amount on line 22 will be sent separately from any refund you claimed on your original return” and “We will figure any interest and include it in your refund.” Also, “A refund on a paperfiled amended return can’t be deposited directly to your bank account.”
Line 23 is captioned “Amount of line 21 you want applied to your (enter year): estimated tax”. The instructions say “Enter on line 23 the amount, if any, from line 21 you want applied to your estimated tax for next year.” “Also enter that tax year in the space provided.” “No interest will be paid on this amount.” “You can’t change your election to apply part or all of the overpayment on line 21 to next year’s estimated tax.”
Where the number comes from
Line 18 comes from your original return or an IRS adjustment, line 19 from lines 17 and 18, and lines 20 and 21 from the comparison of line 11, column C, with line 19. Lines 22 and 23 divide line 21. The original-return versions of the refund choices are on the Form 1040 lines 34 to 36 page.
Where it goes next
Line 22 is the amount the Part III direct deposit lines refer to: “If you want us to directly deposit the amount shown on line 22 to your checking or savings account”. Part II, where you explain the changes, and Part III are on the Parts II and III page. The dependents section is on the lines 24 to 30 page.
Edition and line numbers
This page reads the December 2025 revision of Form 1040-X and its December 2025 instructions, the current files irs.gov served on 2026-10-18. The form is marked “(Rev. December 2025)” and it amends the return year the filer enters at the top, so the revision date is not the same thing as the year being amended. The form’s own instruction at the top says “Attach a completed Form 1040, 1040-SR, or 1040-NR, with your changes, for the return year entered below”. Check the revision date printed on the form you are filling in and the return year you are amending, and use the line numbers on that revision, because a different revision can number or word its lines differently. The whole form is walked through on the Form 1040-X walkthrough page.
Common mistakes
- Including interest on line 18. The instructions say “Don’t include interest you received on any refund.”
- Expecting a direct deposit on a paper amended return. The instructions say “A refund on a paperfiled amended return can’t be deposited directly to your bank account.”
- Planning to reverse the estimated tax choice later. The instructions say “You can’t change your election to apply part or all of the overpayment on line 21 to next year’s estimated tax.”
Related: Form 1040 line 37, Form 1040 lines 34 to 36, Form 1040 line 38, and Form 1040 line 26.
Sources
- Instructions for Form 1040-X, Amended U.S. Individual Income Tax Return (Rev. December 2025): https://www.irs.gov/pub/irs-pdf/i1040x.pdf
- Form 1040-X, Amended U.S. Individual Income Tax Return (Rev. December 2025): https://www.irs.gov/pub/irs-pdf/f1040x.pdf
Read from the IRS documents linked above on October 18, 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.