U.S. · Tax forms
K-1 box 15 credit codes.
Every partnership credit code and the IRS form it is reported on.
Box 15 of a partnership Schedule K-1 (Form 1065) lists your share of tax credits. Most codes point to a source credit form, such as Form 8586 for the low-income housing credit (codes C and D) or Form 6765 for research (code M), and then to Form 3800, the General Business Credit. Code O is backup withholding and goes to Form 1040 line 25c. Pick a code below to see the form the IRS names for it.
Look up a box 15 code
Result
Box 15 codes (2025 K-1)
| Code | Meaning | Where it goes (per the IRS instructions) |
|---|---|---|
| A | Zero-emission nuclear power production credit | Form 7213, Nuclear Power Production Credit, Part II; or Form 3800, Part III, line 1u |
| B | Credit for production from advanced nuclear power facilities | Form 7213, Part I; or Form 3800, Part III, line 1cc |
| C | Low-income housing credit (section 42(j)(5) applies) | Form 8586, line 4; or Form 3800, Part III, line 4d |
| D | Low-income housing credit (section 42(j)(5) does not apply) | Form 8586, line 4; or Form 3800, Part III, line 4d |
| E | Qualified rehabilitation expenditures (rental real estate) | Form 3468. Combine with box 20 code D, which holds the expenditures not related to rental real estate |
| F | Other rental real estate credits | The partnership identifies the credit on an attached statement; passive activity limits and Form 8582-CR may apply |
| G | Other rental credits | The partnership identifies the credit on an attached statement; passive activity limits and Form 8582-CR may apply |
| H | Undistributed capital gains credit | Schedule 3 (Form 1040), Part II, line 13a (tax paid on undistributed capital gains by a RIC or REIT) |
| I | Biofuel producer credit | Form 6478, Biofuel Producer Credit, line 3; or Form 3800, Part III, line 4c (see Tip , earlier) |
| J | Work opportunity credit | Form 5884, Work Opportunity Credit, line 3; or Form 3800, Part III, line 4b (see Tip , earlier) |
| K | Disabled access credit | Form 8826, Disabled Access Credit, line 7; or Form 3800, Part III, line 1e (see Tip , earlier) |
| L | Empowerment zone employment credit | Form 8844, Empowerment Zone Employment Credit, line 3; or Form 3800, Part III, line 3 (see Tip , earlier) |
| M | Credit for increasing research activities | Form 6765, line 29; or Form 3800, Part III, line 4i if you and the partnership are eligible small businesses, otherwise line 1c |
| N | Credit for employer social security and Medicare taxes | Form 8846, Credit for Employer Social Security and Medicare Taxes Paid on Certain Employee Tips, line 5; or Form 3800, Part III, line 4f (see Tip , earlier) |
| O | Backup withholding | Included in the total on Form 1040 or 1040-SR, line 25c; attach a copy of the Schedule K-1 or give the partnership’s details in a statement |
| P | Unused investment credit from the qualifying advanced coal project credit or qualifying gasification project credit allocated from cooperatives | Form 3468, Part II, line 6 |
| Q | Unused investment credit from the qualifying advanced energy project credit allocated from cooperatives | Form 3468, Part III, line 2 |
| R | Unused investment credit from the advanced manufacturing investment credit allocated from cooperatives | Form 3468, Part IV, line 2 |
| S | Unused investment credit from the clean electricity investment credit allocated from cooperatives | Form 3468, Part V, Section C, line 10 |
| T | Unused investment credit from the energy credit allocated from cooperatives | Form 3468, Part VI, Section N, line 31 |
| U | Unused investment credit from the rehabilitation credit allocated from cooperatives | Form 3468, Part VII, line 2 |
| V | Advanced manufacturing production credit | Form 7207; or Form 3800, Part III, line 1b |
| W | Clean electricity production credit | Form 7211; or Form 3800, Part III, line 1gg |
| X | Clean fuel production credit | Form 7218; or Form 3800, Part III, line 1q |
| Y | Clean hydrogen production credit | Form 7210; or Form 3800, Part III, line 1g |
| Z | Orphan drug credit | Form 8820; or Form 3800, Part III, line 1h |
| AA | Enhanced oil recovery credit | Form 8830; or Form 3800, Part III, line 1t |
| AB | Renewable electricity production credit | Form 8835; or Form 3800, Part III, line 1f |
| AC | Biodiesel, renewable diesel, or sustainable aviation fuels credit | Form 8864, line 10 if no statement is attached; otherwise follow the statement and the Form 8864 instructions |
| AD | New markets credit | Form 8874; or Form 3800, Part III, line 1i |
| AE | Small employer pension plan startup costs credit and contributions credit | Form 8881, Part I; or Form 3800, Part III, line 1j |
| AF | Small employer auto-enrollment credit | Form 8881, Part II; or Form 3800, Part III, line 1dd |
| AG | Small employer military spouse participation credit | Form 8881, Part III; or Form 3800, Part III, line 1ee |
| AH | Credit for employer-provided childcare facilities and services | Form 8882; or Form 3800, Part III, line 1k |
| AI | Low sulfur diesel fuel production credit | Form 8896; or Form 3800, Part III, line 1m |
| AJ | Qualified railroad track maintenance credit | Form 8900; or Form 3800, Part III, line 4g |
| AK | Credit for oil and gas production from marginal wells | Form 8904; or Form 3800, Part III, line 1bb |
| AL | Distilled spirits credit | Form 8906; or Form 3800, Part III, line 1n |
| AM | Energy efficient home credit | Form 8908; or Form 3800, Part III, line 1p |
| AN | Reserved for future use | None |
| AO | Alternative fuel vehicle refueling property credit | Form 8911, Part I; or Form 3800, Part III, line 1s |
| AP | Clean renewable energy bond credit | Form 8912 |
| AQ | New clean renewable energy bond credit | Form 8912 |
| AR | Qualified energy conservation bond credit | Form 8912 |
| AS | Qualified zone academy bond credit | Form 8912 |
| AT | Qualified school construction bond credit | Form 8912 |
| AU | Build America bond credit | Form 8912 |
| AV | Credit for employer differential wage payments | Form 8932; or Form 3800, Part III, line 1w |
| AW | Carbon oxide sequestration credit | Form 8933, Part III, line 8; or Form 3800, Part III, line 1x |
| AX | Carbon oxide sequestration credit recapture | Form 8933, Part III, line 10 |
| AY | New clean vehicle credit | Form 8936, Part II; or Form 3800, Part III, line 1y. For limitations on this credit that apply to some taxpayers, see New Clean Vehicle Certification and Other Requirements in the Instructions for Form 8936 |
| AZ | Credit for qualified commercial clean vehicles | Form 8936, Part V; or Form 3800, Part III, line 1aa |
| BA | Credit for small employer health insurance premiums | Form 8941; or Form 3800, Part III, line 4h |
| BB | Employer credit for paid family and medical leave | Form 8994; or Form 3800, Part III, line 4j |
| BC | Eligible credits from transferor(s) under section 6418 | Form 3800; see the Form 3800 instructions, Parts III and V |
| ZZ | Other | Any other information you need to file your return; see the partnership’s statement. Credits retained after a section 6418 transfer election go on Form 3800, Part III, line 4a (section 48), line 1d (48C) or line 1v (48E) |
| BD-BG | Reserved for future use | None |
Reading box 15
The partnership reports your share of each credit, and you complete the credit form the instructions name. For most credits you can use the source form or, when the credit is your only source for a Form 3800 Part III credit and you are not a partnership or S corporation, you may report it directly on Form 3800 Part III. The IRS lists exceptions to that shortcut: you are claiming the investment credit on Form 3468 or the biodiesel credit on Form 8864, the taxpayer is an estate or trust that can allocate the credit to beneficiaries, or the taxpayer is a cooperative that can or must allocate it to patrons.
Credits that are passive activity credits to you also require Form 8582-CR (Form 8810 for corporations) in addition to the credit forms.
Worked example
Priya has $1,200 in box 15 code M and $300 in code O. Code M is the credit for increasing research activities. It goes on Form 6765 line 29 and then Form 3800 Part III, on line 1c unless both she and the partnership are eligible small businesses, in which case line 4i. Code O is her share of backup withholding. It is added to the total on Form 1040 line 25c and a copy of the K-1 is attached to her return, or the K-1 information is given in a statement.
Related codes elsewhere on the K-1
Qualified rehabilitation expenditures for property that is not rental real estate are in box 20 code D, and the instructions tell you to combine them with box 15 code E for Form 3468. Codes AN and BD through BG are reserved for future use.
More form decoders
The capital gains tax calculator and the 1099-R box 7 lookup cover other form codes. K-1 box 20 and box 13 decoders are in the same family of pages.
Sources
- Instructions for Schedule K-1 (Form 1065) (2025): Box 15, Credits, codes A through ZZ, and the Form 3800 tip. Read November 2, 2026.
IRS page last reviewed April 30, 2026. Form and line references are those printed in the 2025 instructions and can change.
Frequently asked questions
What is box 15 on a partnership K-1?
Box 15 reports your share of the partnership’s tax credits. Each code names a type of credit and the IRS form where it is claimed.
Where do I report K-1 box 15 code M?
Code M is the credit for increasing research activities. Report it on Form 6765 line 29, or on Form 3800 Part III, line 1c, or line 4i if you and the partnership are both eligible small businesses.
What are codes C and D in box 15?
They are the low-income housing credit. Code C is used if section 42(j)(5) applies and code D if it does not. Either is reported on Form 8586 line 4 or Form 3800 Part III line 4d.
What is box 15 code O?
It is your share of the credit for backup withholding on dividends, interest and other income. Include it in the total on Form 1040 line 25c and attach a copy of the Schedule K-1 or provide the partnership information in a statement.
Do I always need Form 3800?
Not always. Several codes name their own form, such as Form 8586, Form 6765 or Form 8826, and many say Form 3800 as the alternative. Check the form named for your code.
Not tax advice
This page summarizes IRS instructions, mostly written for the people who prepare the form, and is not tax, legal or financial advice. The payer, a CPA or an enrolled agent can confirm what a box or code means for your return. Everything runs in your browser; nothing you enter is sent anywhere.