Updated October 18, 2026. Quick answer: Line 17 adds the right-hand column amounts for lines 4 through 16 and carries the total to Form 1040 line 12e. Line 18 is a box you check only if you choose to itemize even though your itemized deductions are less than your standard deduction.
IRS worksheets read line by line: Worksheet 2, Recoveries of Itemized Deductions.
What line 17 asks for
The caption reads “Add the amounts in the far right column for lines 4 through 16. Also, enter this amount on Form 1040 or 1040-SR, line 12e”. The lines that feed the right-hand column are: lines 1 to 4, the taxes lines, the interest lines (Schedule A lines 9 and 10), the gifts lines (Schedule A lines 13 and 14), Schedule A line 15 and Schedule A line 16.
Why you itemize at all
The instructions say “Use Schedule A (Form 1040) to figure your itemized deductions.” They add “In most cases, your federal income tax will be less if you take the larger of your itemized deductions or your standard deduction.” The choice is covered on the Form 1040 line 12 page.
Do not repeat items deducted elsewhere
The instructions say “Don’t include on Schedule A items deducted elsewhere”. The instructions add that the new deductions for tips, overtime, car loan interest and seniors go on Schedule 1-A: “If you are eligible, you will claim these deductions on Schedule 1-A, not on Schedule A.”
Line 18: the itemizing box
The caption reads “If you elect to itemize deductions even though they are less than your standard deduction, check this box”. The instruction is “If you elect to itemize for state tax or other purposes even though your itemized deductions are less than your standard deduction, check the box on line 18.”
Where the number comes from
Line 17 is the sum of the amounts in the far right column for lines 4 through 16. Check each of those lines first, because the instructions say what belongs on each. The whole form is explained on the Schedule A (Form 1040) page.
Where it goes next
Line 17 is entered on Form 1040 or 1040-SR, line 12e, as the form’s caption says. See the Form 1040 line 12 page and the Form 1040 page for the Form 1040 side. For lines that sit just before this total, see Schedule A line 16.
Edition and line numbers
This page reads the 2025 Schedule A (Form 1040) and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040 or 1040-SR.” Check the tax year printed on the schedule you are filling in and use the line numbers on that year’s schedule, because a different year’s schedule can number or word its lines differently.
Common mistakes
- Entering the total on the wrong Form 1040 line. The caption says to enter it “on Form 1040 or 1040-SR, line 12e”.
- Counting an item twice. The instructions say “Don’t include on Schedule A items deducted elsewhere”.
- Checking the line 18 box by default. The instructions limit it to a choice to “itemize for state tax or other purposes even though your itemized deductions are less than your standard deduction”.
Related: Schedule A (Form 1040), Form 1040 line 12, and Form 1040.
Sources
- Instructions for Schedule A (Form 1040), Itemized Deductions (2025): https://www.irs.gov/pub/irs-pdf/i1040sca.pdf
- Schedule A (Form 1040), Itemized Deductions (2025): https://www.irs.gov/pub/irs-pdf/f1040sa.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.