Updated October 17, 2026. Quick answer: Line 37 of Form 1040 is the amount you owe. You get it by subtracting line 33, your total payments, from line 24, your total tax. Any estimated tax penalty from line 38 is included in it, and the instructions say to pay in full by the due date of your return, not counting extensions.
More IRS forms and schedules, read line by line: Form 1040-V payment voucher.
Related reading on this site: IRS Notice CP11 (return corrected, amount owed changed), IRS Notice CP11 (return corrected, amount owed changed), IRS Notice CP12 (refund created or changed) and IRS Notice CP13 (return corrected, zero balance).
Business use of your home (Form 8829), the saver’s credit (Form 8880), clean vehicle credits (Form 8936) and amended returns (Form 1040-X), read line by line: Form 1040-X, Form 1040-X lines 18 to 23 and Form 1040-X Parts II and III.
Form 8962 (premium tax credit) for 2025, read line by line: Form 8962 line 26 and Form 8962 line 29.
Schedule 3 (Form 1040) for 2025, read line by line: Schedule 3 line 10, Schedule 3 line 12 and Schedule 3 lines 13a to 13d.
What line 37 asks for
The form’s caption for line 37 reads “Subtract line 33 from line 24. This is the amount you owe.” It then points you to payment help: “For details on how to pay, go to www.irs.gov/Payments or see instructions”. Line 37 is only filled in when your total tax on line 24 is more than your total payments on line 33. When it is the other way round, the difference is an overpayment on line 34.
Where the number comes from
Line 37 is a subtraction of two totals you have already reached. Line 24 is the form’s total tax, with the caption “Add lines 22 and 23. This is your total tax”. Line 33 is the total of payments and refundable credits, with the caption “Add lines 25d, 26, and 32. These are your total payments”. The two totals are explained on the pages for lines 32 and 33 and in Form 1040 line by line.
A labelled illustration, not an IRS example, of the form’s arithmetic, computed from made up numbers: if line 24 is $8,800 and line 33 is $7,000 then line 37 is computed as $8,800 minus $7,000 which is $1,800. The figures are made up to show the arithmetic only.
The estimated tax penalty is part of line 37
The instructions say “Include any estimated tax penalty from line 38 in the amount you enter on line 37.” The line 38 page, Form 1040 line 38, explains the penalty itself. The instructions also separate this payment from your next year’s estimated payments: “Don’t include any estimated payments for 2026 in this payment.” Those are made separately, as described on the Form 1040-ES page.
When to pay
The timing rule is stated this way: “To avoid interest and penalties, pay your taxes in full by the due date of your return (not including extensions)”. It also says “You don’t have to pay if line 37 is under $1.” The due date for the return is covered on the Form 1040 due date page. An extension of time to file is a separate request, described on the Form 4868 page.
How to pay online
The instructions open with “The IRS offers several payment options.” and recommend the online route: “Paying online is convenient and secure and helps make sure we get your payments on time.” The starting point is “To pay your taxes online or for more information, go to IRS.gov/ModernPayments.”
Two of the online methods are described this way. Online account: “You can make tax payments through your online account, including balance payments, estimated tax payments, or other types.” Direct Pay: “For online transfers directly from your checking or savings account at no cost to you, go to IRS.gov/Payments.” For cards, they say “A fee is charged by these service providers.”
Other ways to pay
The instructions also cover phone, cash and mail. On cash they say “You can pay your taxes in cash.” and then “Don’t send cash payments through the mail.” If you do mail a payment, “attach Form 1040-V”. The instructions add a note before that: “Before submitting a payment through the mail, please consider alternative methods.”
Where it goes next
Line 37 is the last total of the amount-you-owe section on the return. The next line on the form is line 38, whose caption reads “Estimated tax penalty (see instructions)”. The instructions tie the two together: “Add the penalty to any tax due and enter the total on line 37.” After line 38, the form moves on to the third party designee and signature sections.
Edition and line numbers
This page reads the 2025 Form 1040 and its 2025 instructions, the current files irs.gov served on 2026-10-17. They are the forms for the tax year 2025 return, filed in 2026. The instructions say “The lines on Forms 1040 and 1040-SR are the same.” so everything here applies to Form 1040 and to Form 1040-SR alike. Check the tax year printed on the form you are filling in and use the line numbers on that year’s form, because a different year’s form can number or word its lines differently.
Common mistakes
- Forgetting the penalty. The instructions say “Include any estimated tax penalty from line 38 in the amount you enter on line 37.”
- Putting next year’s estimated payment inside the line 37 payment. The instructions say “Don’t include any estimated payments for 2026 in this payment.”
- Mailing cash. The instructions say “Don’t send cash payments through the mail.”
Related: Form 1040 due date, Form 4868, Form 1040-ES, and Form 1040.
Sources
- Instructions for Form 1040 and Form 1040-SR (2025): https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
- Form 1040, U.S. Individual Income Tax Return (2025): https://www.irs.gov/pub/irs-pdf/f1040.pdf
Read from the IRS documents linked above on October 17, 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.