Updated October 16, 2026. Quick answer: Box 14 of Schedule K-1 (Form 1120-S) tells a shareholder whether a Schedule K-3 is attached, and box 15 reports alternative minimum tax items by code A through F. The 2025 instructions say “Use the information reported in box 15 (as well as your adjustments and tax preference items from other sources) to prepare your Form 6251”. Codes A through C give the Form 6251 line for an individual shareholder.
What boxes 14 and 15 report
On the form, box 14 reads “Schedule K-3 is attached if” followed by a check box, and line 15 is labelled “Alternative minimum tax (AMT) items”. This page covers the shareholder’s side of a K-1 you received. Every other box is set out on the Schedule K-1 (Form 1120-S) boxes overview.
“In boxes 10, 12, 13, and 15 through 17, the corporation will identify each item by entering a code in the column to the left of the dollar amount entry space.”
Box 14: the Schedule K-3 check box
Box 14 has two outcomes, depending on whether the corporation checked the box. “If the S corporation checked the box, see the attached Schedule K-3 with respect to items of international tax relevance.”
If the box is not checked, a statement takes the place of the schedule: “If the S corporation did not check the box, the S corporation attached a statement to the Schedule K-1 (or issued a statement prior to furnishing the Schedule K-1) notifying the shareholder that the shareholder will not receive Schedule K-3 from the S corporation unless the shareholder requests the schedule.”
For more, “see the Shareholder’s Instructions for Schedule K-3 (Form 1120-S).” Foreign tax credit questions that start from the K-3 lead to the Form 1116 page.
Box 15: how the codes are used
“Use the information reported in box 15 (as well as your adjustments and tax preference items from other sources) to prepare your Form 6251”, or the estate and trust alternative minimum tax schedule. The individual form is covered on the Form 6251 page.
Every box 15 code and where it goes
The table follows the instructions code by code. The line numbers are the ones the 2025 instructions print for an individual shareholder.
| Code | What it is, as printed | Where it goes |
|---|---|---|
| A | “Post-1986 depreciation adjustment.” | “If you are an individual shareholder, report this amount on Form 6251, line 2l.” |
| B | “Adjusted gain or loss.” | “If you are an individual shareholder, report this amount on Form 6251, line 2k.” |
| C | “Depletion (other than oil & gas).” | “If you are an individual shareholder, report this amount on Form 6251, line 2d.” |
| D and E | Oil, gas, & geothermal properties “gross income (code D) from, and deductions (code E) allocable to, oil, gas, and geothermal properties included in box 1 of Schedule K-1” | “Use the amounts reported here and any other reported amounts to help you figure the net amount to enter on Form 6251, line 2t.” |
| F | “Other AMT items.” | “Report the information on the statement attached by the corporation on the applicable lines of Form 6251 or Schedule I (Form 1041).” |
Codes D and E: oil, gas and geothermal properties
These two codes work as a pair. “The amounts reported on these lines include only the gross income (code D) from, and deductions (code E) allocable to, oil, gas, and geothermal properties included in box 1 of Schedule K-1.” “The corporation should have attached a statement that shows any income from, or deductions allocable to, such properties that are included in boxes 2 through 12, 16, and 17 of Schedule K-1.”
Code F: other AMT items
“Report the information on the statement attached by the corporation on the applicable lines of Form 6251 or Schedule I (Form 1041).” The statement is the source, so a code F amount cannot be placed from the box alone.
Limits that apply before the amounts reach the return
The instructions list four limits and put them in a fixed order: “These limitations and the order in which you must apply them are as follows: the basis limitations, the at-risk limitations, the passive activity limitations, and the excess business loss limitations.” The amounts printed in Part III are before any of them. “The amounts shown in boxes 1 through 17 reflect your share of income, loss, deductions, credits, and other items from corporate business or rental activities without reference to limitations on losses, credits, or other items”.
Basis is the shareholder’s own job to track. “Any losses and deductions not allowed this year because of the basis limit can be carried forward indefinitely and deducted in a later year subject to the basis limit for that year.” “You are responsible for keeping the information needed to figure the basis of your stock in the corporation.”
Passive losses are figured on their own form. “If you have a passive activity loss or credit, use Form 8582, Passive Activity Loss Limitations, to figure your allowable passive losses”. The form is covered on the Form 8582 page.
For the at-risk step, “you will have to complete Form 6198, At-Risk Limitations, to figure your allowable loss for the activity.” Form 6198 is covered on the Form 6198 page.
Other K-1 pages on this site
The partnership version of this form is read on the Schedule K-1 (Form 1065) boxes page. Estates and trusts receive a third version, covered on the estates Schedule K-1 page.
Which revision applies
The edition read for this page is the 2025 Shareholder’s Instructions for Schedule K-1 (Form 1120-S) and the 2025 Schedule K-1 (Form 1120-S) itself, which are the revisions irs.gov served when they were read on 2026-10-16. Check the revision printed on the Schedule K-1 you received and the matching instructions, because a later edition can change the box layout, the code letters and the reporting lines.
Common mistakes
- Ignoring box 14 when it is checked. The instructions say that when the box is checked, the attached Schedule K-3 holds the items of international tax relevance, and it is the source for foreign tax reporting.
- Placing a code F amount from the box. The instructions say to report the information on the statement the corporation attached, on the applicable lines of Form 6251 or Schedule I (Form 1041).
- Entering codes D and E separately. The instructions say to use the amounts reported with any other reported amounts to figure the net amount to enter on Form 6251, line 2t.
Related: Form 6251 alternative minimum tax, Form 1116 foreign tax credit, Schedule K-1 (Form 1065) boxes explained, and Schedule K-1 for estates.
Sources
- 2025 Shareholder’s Instructions for Schedule K-1 (Form 1120-S): https://www.irs.gov/pub/irs-pdf/i1120ssk.pdf
- Schedule K-1 (Form 1120-S) (2025), Shareholder’s Share of Income, Deductions, Credits, etc.: https://www.irs.gov/pub/irs-pdf/f1120ssk.pdf
Read from the IRS documents linked above on October 16, 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.