Updated October 18, 2026. Quick answer: Lines 13 to 18 finish Part II, the ordinary gains and losses part of Form 4797. Line 13 picks up the gain from line 31 of Part III, lines 14 to 16 bring in amounts from other forms, line 17 combines lines 10 through 16, and line 18 sends the total on to your return. Individuals complete lines 18a and 18b to take out a loss on income-producing property.
What this part of Part II covers
Part II carries the caption “Ordinary Gains and Losses (see instructions)”. The instructions send a transaction here when “If a transaction is not reportable in Part I or Part III and the property is not a capital asset reportable on Schedule D, report the transaction in Part II.” Lines 10 to 12 come first and are covered on the lines 10 to 12 page. This page picks up at line 13. The gain or loss in the amounts below flows into one total on line 17, so it is worth reading Part II from the top to bottom before you start.
Line 13: the gain from line 31
The form’s caption is “Gain, if any, from line 31”. Line 31 sits in Part III, which has its own page; see lines 25 to 32. The instructions confirm the link in another place: “Use Part III of Form 4797 to figure the amount of ordinary income recapture. The recapture amount is included on line 31 (and line 13) of Form 4797.” The instructions have no separate paragraph headed with line 13, so the form caption and that sentence are the whole guide for the line. Line 31 itself says to enter the amount “Enter here and on line 13”.
Lines 14, 15 and 16: amounts from other forms
These three lines are labels for amounts you carry in from other forms. The captions read “Net gain or (loss) from Form 4684, lines 31 and 38a”, “Ordinary gain from installment sales from Form 6252, line 25 or 36” and “Ordinary gain or (loss) from like-kind exchanges from Form 8824”. The instructions have no separate paragraph for lines 14, 15 or 16 (a search of the Part II instructions finds only the paragraphs for line 10 and line 18a), so the amount comes from the line of the other form that the caption names. The casualty and theft side is on the Form 4684 page, and the exchange side is on the Form 8824 page.
Line 17: combining lines 10 through 16
Line 17 is “Combine lines 10 through 16”. That adds the ordinary gains and losses together, with losses as negative amounts, so the result can be a gain or a loss.
A short illustration of that arithmetic (computed illustration, not an IRS example): if line 10 were a gain of $4,000 and line 13 were a gain of $1,500, then line 17 would be computed as $4,000 plus $1,500, which is $5,500, when every other line in the range is blank.
Line 18: where the total goes
The form splits line 18 by who is filing. It says “For all except individual returns, enter the amount from line 17 on the appropriate line of your return and skip lines a and b below.” It then says “For individual returns, complete lines a and b below.”
Line 18a is the first of two steps. The form asks for “If the loss on line 11 includes a loss from Form 4684, line 35, column (b)(ii), enter that part of the loss here.” The instructions say when it is required: “complete this line if there is a gain on Form 4797, line 3; a loss on Form 4797, line 11; and a loss on Form 4684, line 35, column (b)(ii).” They then say how to pick the amount: “Enter on this line the smaller of the loss on Form 4797, line 11, or the loss on Form 4684, line 35, column (b)(ii).” The method for comparing: “which loss is smaller, treat both losses as positive numbers.”
The loss goes elsewhere: “Enter the loss from income-producing property on Schedule A (Form 1040), line 16.” The instructions add “Do not include any loss from property used as an employee.”
Line 18b is the remainder. The caption is “Redetermine the gain or (loss) on line 17 excluding the loss, if any, on line 18a.” It adds “Enter here and on Schedule 1 (Form 1040), Part I, line 4”. The instructions have no separate paragraph for line 18b. Business gains on Schedule 1 are described on the Schedule 1 lines 3 to 6 page.
Where the number comes from
Line 13 comes from line 31 of Part III on the same form. Lines 14, 15 and 16 come from the other forms named in their captions. Line 17 and line 18b are arithmetic, and line 18a comes from line 11 of this form and line 35 of Form 4684. Gains that are not ordinary come through Part I and Schedule D; see the Schedule D page.
Where it goes next
For an individual return, line 18b is the figure that goes “Enter here and on Schedule 1 (Form 1040), Part I, line 4”, and the line 18a loss goes to Schedule A as quoted above. Part III is the next part of the form; its first lines are on the lines 19 to 24 page.
Edition and line numbers
This page reads the 2025 Form 4797, Sales of Business Property, 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 form header says “Attach to your tax return.” 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. The whole form is walked through on the Form 4797 line by line guide page.
Common mistakes
- Putting a loss from property used as an employee on line 18a. The instructions say “Do not include any loss from property used as an employee.”
- Comparing the two losses with their signs. The instructions say “which loss is smaller, treat both losses as positive numbers.”
- Completing lines 18a and 18b on a return that is not an individual return. The form says “For all except individual returns, enter the amount from line 17 on the appropriate line of your return and skip lines a and b below.”
Related: Form 4684, Form 8824, Schedule 1 lines 3 to 6, and Schedule D.
Sources
- Instructions for Form 4797, Sales of Business Property (2025): https://www.irs.gov/pub/irs-pdf/i4797.pdf
- Form 4797, Sales of Business Property (2025): https://www.irs.gov/pub/irs-pdf/f4797.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.