Updated October 18, 2026. Quick answer: Line 15 is for personal casualty and theft losses from a federally declared disaster. The amount comes from line 18 of Form 4684, which you attach. A net qualified disaster loss does not go here; it goes on line 16.
Related reading on this site: IRS Publication 547.
Form lines read one part at a time: Form 4684 Section A and Form 4684 Sections C and D.
What line 15 asks for
The caption reads “Casualty and theft loss(es) from a federally declared disaster (other than net qualified disaster losses). Attach Form 4684 and enter the amount from line 18 of that form.” The instructions say “Complete and attach Form 4684 to figure the amount of your loss. Only enter the amount from Form 4684, line 18, on line 15.” The form is covered on the Form 4684 page.
What the instructions allow
The limits are stated in two parts. The instructions say you “can only deduct personal casualty and theft losses attributable to a federally declared disaster to the extent that:” the first is “The amount of each separate casualty or theft loss is more than $100, and” the second is “The total amount of all losses during the year (reduced by the $100 limit discussed in (1)) is more than 10% of the amount on Form 1040 or 1040-SR, line 11b.” For more, the instructions say “See the Instructions for Form 4684 and Pub. 547 for more information.” Background on how the rules changed is on the casualty losses after TCJA page.
Net qualified disaster losses
The instructions warn “Don’t enter a net qualified disaster loss from Form 4684, line 15, on line 15. Instead, enter that amount, if any, on line 16.” The form’s top caution adds “If you are claiming a net qualified disaster loss on Form 4684, see the instructions for line 16.” That is covered on the Schedule A line 16 page.
Where the number comes from
The figure is read from Form 4684, not figured on Schedule A. The instruction is “Only enter the amount from Form 4684, line 18, on line 15.”
Where it goes next
Line 15 is counted in the total on line 17, which reads “Add the amounts in the far right column for lines 4 through 16.” See the Schedule A lines 17 and 18 page for that step and the Schedule A (Form 1040) page for the whole form.
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 a net qualified disaster loss on line 15. The instructions say “Don’t enter a net qualified disaster loss from Form 4684, line 15, on line 15.”
- Entering a different Form 4684 line. The instructions say “Only enter the amount from Form 4684, line 18, on line 15.”
- Leaving out the 10% test. The instructions require that the total of all losses “is more than 10% of the amount on Form 1040 or 1040-SR, line 11b.”
Related: Schedule A (Form 1040), Form 4684, and casualty losses after TCJA.
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.