Updated October 16, 2026. Quick answer: Box 13 of Schedule K-1 (Form 1120-S) is a shareholder’s share of the S corporation’s tax credits, and each lettered code names its own credit form. The 2025 instructions open with a rule for passive credits: “If you have credits that are passive activity credits to you, you must complete Form 8582-CR in addition to the credit forms identified below.” Most codes also point to a line of Form 3800, so read the code letter first.
What box 13 reports
On the form, line 13 of Part III is labelled Credits. Each credit is identified by a code, and the instructions treat each code on its own. This page covers the shareholder’s side of a K-1 you received, not how the corporation files its own return. 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.”
Passive credits and Form 8582-CR
Credits can be limited the same way losses are. “If you have credits that are passive activity credits to you, you must complete Form 8582-CR in addition to the credit forms identified below.” “See Passive Activity Limitations, earlier, and the Instructions for Form 8582-CR for details.”
The general passive rule appears in the instructions as “If you have a passive activity loss or credit, use Form 8582, Passive Activity Loss Limitations, to figure your allowable passive losses, and Form 8582-CR, Passive Activity Credit Limitations, to figure your allowable passive credits.” Passive losses are covered on the Form 8582 page.
The Form 3800 Tip
Most codes give two destinations, the credit’s own form or Form 3800. The Tip explains when a shareholder can skip the credit form. “In general, shareholders whose only sources for a credit listed in Form 3800, General Business Credit, Part III, are partnerships, S corporations, estates, trusts, and cooperatives, aren’t required to complete the applicable credit form or attach it to their return.” “Instead, they can report the credit amounts reported to them by these pass-through entities directly in Form 3800, Part III, and enter the EIN of the entity in column (c) of Part III.”
The Tip has an exception: “However, when applicable, all shareholders must complete and attach the following credit forms to their return.” The two forms named are “Form 3468, Investment Credit (Form 3800, Part III, line 1a).” and “Form 8864, Biodiesel, Renewable Diesel, or Sustainable Aviation Fuels Credit (Form 3800, Part III, line 1l).” “See the Instructions for Form 3800 for more details.”
Every box 13 code and where it goes
The table follows the instructions code by code. The middle column is the credit as the instructions print it and the right column is the reporting sentence. The codes marked reserved carry no instruction.
| Code | Credit, as printed | Where the instructions say to report it |
|---|---|---|
| A | “Zero-emission nuclear power production credit.” | “Report this amount in Part II of Form 7213, Nuclear Power Production Credit, or on Form 3800, Part III, line 1u (see Tip, earlier).” |
| B | “Credit for production from advanced nuclear power facilities.” | “Report this amount in Part I of Form 7213, or on Form 3800, Part III, line 1cc (see Tip, earlier).” |
| C and D | “Low-income housing credit.” | “Any allowable low-income housing credit reported using code C or D is reported on Form 8586, Low-Income Housing Credit, line 4, or Form 3800, Part III, line 4d (see Tip, earlier).” |
| E | “Qualified rehabilitation expenditures (rental real estate).” | “Your share of qualified rehabilitation expenditures from property not related to rental real estate activities will be reported in box 17 using code C.” “See the Instructions for Form 3468 for details.” |
| F | “Other rental real estate credits.” | “These credits may be limited by the passive activity limitations.” “See Passive Activity Limitations, earlier, and the Instructions for Form 8582-CR for details.” |
| G | “Other rental credits.” | “These credits may be limited by the passive activity limitations.” “See Passive Activity Limitations, earlier, and the Instructions for Form 8582-CR for details.” |
| H | “Undistributed capital gains credit.” | “Report these taxes on Schedule 3 (Form 1040), Additional Credits and Payments, line 13a.” “Reduce the basis of your stock by this tax.” |
| I | “Biofuel producer credit.” | “Report this amount on line 3 of Form 6478, Biofuel Producer Credit, or Form 3800, Part III, line 4c (see Tip, earlier).” |
| J | “Work opportunity credit.” | “Report this amount on line 3 of Form 5884, Work Opportunity Credit, or Form 3800, Part III, line 4b (see Tip, earlier).” |
| K | “Disabled access credit.” | “Report this amount on line 7 of Form 8826, Disabled Access Credit, or Form 3800, Part III, line 1e (see Tip, earlier).” |
| L | “Empowerment zone employment credit.” | “Report this amount on line 3 of Form 8844, Empowerment Zone Employment Credit, or Form 3800, Part III, line 3 (see Tip, earlier).” |
| M | “Credit for increasing research activities.” | “Report this amount on Section C, line 29, of Form 6765, Credit for Increasing Research Activities, or Form 3800, Part III, line 1c (see Tip, earlier), as follows.” “If you and the S corporation are eligible small businesses, report the credit on line 4i.” “All others, report the credit on line 1c.” |
| N | Credit for employer social security and Medicare taxes. | “Report this amount on line 5 of Form 8846, Credit for Employer Social Security and Medicare Taxes Paid on Certain Employee Tips, or Form 3800, Part III, line 4f (see Tip, earlier).” |
| O | “Backup withholding.” | “Include this amount in the total you enter on Form 1040 or 1040-SR, line 25c, and attach a copy of your Schedule K-1 to your tax return.” |
| P | Unused investment credit from the qualifying advanced coal project credit or qualifying gasification project credit allocated from cooperatives. | “Report this amount on Form 3468, Part II, line 6.” |
| Q | Unused investment credit from the qualifying advanced energy project credit allocated from cooperatives. | “Report this amount on Form 3468, Part III, line 2.” |
| R | Unused investment credit from the advanced manufacturing investment credit allocated from cooperatives. | “Report this amount on Form 3468, Part IV, line 2.” |
| S | Unused investment credit from clean electricity credit allocated from cooperatives. | “Report this amount on Form 3468, Part V, line 10.” |
| T | “Unused investment credit from the energy credit allocated from cooperatives.” | “Report this amount on Form 3468, Part VI, line 31.” |
| U | Unused investment credit from the rehabilitation credit allocated from cooperatives. | “Report this amount on Form 3468, Part VII, line 2.” |
| V | “Advanced manufacturing production credit.” | “Report on Form 7207, Advanced Manufacturing Production Credit, or Form 3800, Part III, line 1b (see Tip, earlier).” |
| W | “Clean electricity production credit.” | “Report on Form 7211, Clean Electricity Production Credit, or Form 3800, Part III, line 1gg (see Tip, earlier).” |
| X | “Clean fuel production credit.” | “Report on Form 7218, Clean Fuel Production Credit, or Form 3800, Part III, line 1q (see Tip, earlier).” |
| Y | “Clean hydrogen production credit.” | “Report this amount on Form 7210, Clean Hydrogen Production Credit, or Form 3800, Part III, line 1g (see Tip, earlier).” |
| Z | “Orphan drug credit.” | “Report this amount on Form 8820, Orphan Drug Credit, or Form 3800, Part III, line 1h (see Tip, earlier).” |
| AA | “Enhanced oil recovery credit.” | “Report this amount on Form 8830, Enhanced Oil Recovery Credit, or Form 3800, Part III, line 1t (see Tip, earlier).” |
| AB | “Renewable electricity production credit.” | “The corporation will provide a statement showing the allocation of the credit for production during the 4-year period beginning on the date the facility was placed in service and for production after that period.” “Report this amount on Form 8835, Renewable Electricity Production Credit, or Form 3800, Part III, line 1f (see Tip, earlier).” |
| AC | “Biodiesel, renewable diesel, or sustainable aviation fuels credit.” | “If no statement is attached, report this amount on Form 8864, line 10. If a statement is attached, see the instructions for Form 8864, line 10.” |
| AD | “New markets credit.” | “Report this amount on Form 8874, New Markets Credit, or Form 3800, Part III, line 1i (see Tip, earlier).” |
| AE | “Credit for small employer pension plan startup costs.” | “Report this amount in Form 8881, Credit for Small Employer Pension Plan Startup Costs, Auto-Enrollment, and Military Spouse Retirement Plan, Part I, or on Form 3800, Part III, line 1j (see Tip, earlier).” |
| AF | “Credit for small employer auto-enrollment.” | “Report this amount in Form 8881, Part II, or on Form 3800, Part III, line 1dd (see Tip, earlier).” |
| AG | “Credit for military spouse participation.” | “Report this amount in Form 8881, Part III, or on Form 3800, Part III, line 1ee (see Tip, earlier).” |
| AH | Credit for employer-provided childcare facilities and services. | “Report this amount on Form 8882 or Form 3800, Part III, line 1k (see Tip, earlier).” |
| AI | “Low sulfur diesel fuel production credit.” | “Report this amount on Form 8896, Low Sulfur Diesel Fuel Production Credit, or Form 3800, Part III, line 1m (see Tip, earlier).” |
| AJ | “Qualified railroad track maintenance credit.” | “Report this amount on Form 8900, Qualified Railroad Track Maintenance Credit, or Form 3800, Part III, line 4g (see Tip, earlier).” |
| AK | Credit for oil and gas production from marginal wells. | “Report this amount on Form 8904, Credit for Oil and Gas Production From Marginal Wells, or Form 3800, Part III, line 1bb (see Tip, earlier).” |
| AL | “Distilled spirits credit.” | “Report this amount on Form 8906, Distilled Spirits Credit, or Form 3800, Part III, line 1n (see Tip, earlier).” |
| AM | “Energy efficient home credit.” | “Report this amount on Form 8908, Energy Efficient Home Credit, or Form 3800, Part III, line 1p (see Tip, earlier).” |
| AN, BD to BG | “Code AN. Reserved for future use.” “Codes BD through BG. Reserved for future use.” | No entry |
| AO | “Alternative fuel vehicle refueling property credit.” | “Report this amount on Form 8911, Alternative Fuel Vehicle Refueling Property Credit, Part I, or Form 3800, Part III, line 1s (see Tip, earlier).” |
| AP | “Clean renewable energy bond credit.” | “Report this amount on Form 8912, Credit to Holders of Tax Credit Bonds.” |
| AQ | “New clean renewable energy bond credit.” | “Report this amount on Form 8912.” |
| AR | “Qualified energy conservation bond credit.” | “Report this amount on Form 8912.” |
| AS | “Qualified zone academy bond credit.” | “Report this amount on Form 8912.” |
| AT | “Qualified school construction bond credit.” | “Report this amount on Form 8912.” |
| AU | “Build America bond credit.” | “Report this amount on Form 8912.” |
| AV | Credit for employer differential wage payments. | “Report this amount on Form 8932, Credit for Employer Differential Wage Payments, or Form 3800, Part III, line 1w (see Tip, earlier).” |
| AW | “Carbon oxide sequestration credit.” | “Report this amount on Form 8933, Carbon Oxide Sequestration Credit, or Form 3800, Part III, line 1x (see Tip, earlier).” |
| AX | Carbon oxide sequestration credit recapture. | “Report the carbon oxide sequestration credit recapture amount on Form 8933, Part III, line 8.” |
| AY | “New clean vehicle credit.” | “Report this amount on Form 8936, Clean Vehicle Credits, Part II, or Form 3800, Part III, line 1y (see Tip, earlier).” |
| AZ | “Qualified commercial clean vehicle credit.” | “Report this amount on Form 8936, Part V, or Form 3800, Part III, line 1aa (see Tip, earlier).” |
| BA | “Credit for small employer health insurance premiums.” | “Report this amount on Form 8941, Credit for Small Employer Health Insurance Premiums, or Form 3800, Part III, line 4h (see Tip, earlier).” |
| BB | Employer credit for paid family and medical leave. | “Report on Form 8994, Employer Credit for Paid Family and Medical Leave, or Form 3800, Part III, line 4j (see Tip, earlier).” |
| BC | “Eligible credits from transferor(s) under section 6418.” | “Report this amount on Form 3800. See the instructions for Form 3800, Parts III and V, for additional information.” |
| ZZ | “Other credits.” | “Most credits identified by code ZZ will be reported in Form 3800, Part III (see Tip, earlier).” |
Low-income housing credit: keep a record by source
Codes C and D carry a record-keeping instruction. “If section 42(j)(5) applies, the corporation will report your share of the low-income housing credit using code C. If section 42(j)(5) doesn’t apply, your share of the credit will be reported using code D.”
“Keep a separate record of the low-income housing credit from each separate source so that you can correctly figure any recapture of low-income housing credit that may result from the disposition of all or part of your stock in the corporation.”
Codes E and F: rehabilitation and rental real estate credits
“Combine the expenditures (for Form 3468 reporting) from box 13, code E, and from box 17, code C.” “The expenditures related to rental real estate activities (box 13, code E) are reported on Schedule K-1 separately from other qualified rehabilitation expenditures (box 17, code C) because they are subject to different passive activity limitation rules.”
For code F, “If the credits are from more than one activity, the corporation will identify the credits from each activity on an attached statement.”
Code O: backup withholding
Code O is a payment, not a business credit. “This is your share of the credit for backup withholding on dividends, interest income, and other types of income.” “Instead of attaching a copy of your Schedule K-1 to your tax return, you can include a statement with your return that provides the corporation’s name, address, EIN, and backup withholding amount.”
Code ZZ and the section 6418 transfer election
“On a statement attached to Schedule K-1, the corporation will identify the type of credit and any other information you need to figure credits other than those reported with codes A through BC.”
Three retained-credit cases carry their own Form 3800 line. For a retained section 48 credit, “report this amount on Form 3800, Part III, line 4a.” For a retained section 48C credit, “report this amount on Form 3800, Part III, line 1d.” For a retained section 48E credit, “report this amount on Form 3800, Part III, line 1v.”
Other K-1 pages on this site
The partnership version of this form is read on the Schedule K-1 (Form 1065) boxes page and the estate and trust version 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
- Skipping the passive credit form. The instructions say a shareholder with passive activity credits must complete Form 8582-CR in addition to the credit forms, and codes F and G add that the credits may be limited by the passive activity limitations.
- Attaching every credit form when it is not needed. The Form 3800 Tip says a shareholder whose only sources are pass-through entities can report the amounts directly in Form 3800, Part III, with the entity’s EIN, except for the Form 3468 and Form 8864 credits.
- Reading code O as a business credit. The instructions describe it as the shareholder’s share of backup withholding, entered on Form 1040 or 1040-SR, line 25c, with a copy of the K-1 or a statement.
Related: Form 8582 passive activity losses, Schedule K-1 (Form 1065) boxes explained, Schedule K-1 for estates, and Schedule K-1 (Form 1041) boxes explained.
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.