Seven places the credit goes missing.

1. The return is a Form 1120-S or 1065. The entity stops at Form 6765, line 30 (less any payroll election on line 36) and reports it on Schedule K: line 13g, code M on Form 1120-S, or line 15f, code M on Form 1065. It never files Form 3800 for this credit. Each owner claims it from the K-1 on their own Form 3800.
2. The payroll election took some of it. For an S corporation or partnership, the amount elected in Form 6765, Section D comes off before Schedule K and goes to Form 8974 and the company's Form 941. A C corporation or sole proprietor reports the full credit on Form 3800 first, and the payroll portion comes out of the credit it couldn't use this year. See the payroll tax credit guide.
3. The limitation allowed zero. The credit is on Part III, but Part II caps what can be used. For an individual, the cap is net income tax minus the greater of the tentative minimum tax or 25 percent of net regular tax above $25,000. When tentative minimum tax sits close to regular tax, a line 1c credit is allowed at little or nothing. For a corporation, the cap leaves 25 percent of net income tax above $25,000 in place.
4. It's on line 1c and belongs on line 4i. Credits of an eligible small business go on Part III, line 4i, and can offset the tentative minimum tax. That alone can turn a zero into a usable credit. An eligible small business is a non-public corporation, a partnership, or a sole proprietorship with average annual gross receipts of $50 million or less over the three prior years. For a K-1 credit, both the entity and the owner must meet that test.
5. It's passive. A credit from a business the owner doesn't materially participate in goes in column (d) before the passive limit. Form 8582-CR then limits it to the tax on passive income, and the allowed amount goes on Part I, line 3.
6. The owner's share is capped. Section 41(g) limits an owner's credit to the tax on their share of income from that business. A pass-through that sends out a loss with the credit can leave the owner with no room this year.
7. The K-1 credit was keyed as a Form 6765. A partner or shareholder with no research of their own enters the K-1 amount straight on Form 3800, Part III, line 1c or 4i, with the entity's EIN in column (c). Keyed into a Form 6765 input instead, tax software can treat it as a credit still to be computed.

Unused credit isn't lost. It carries back one year and forward twenty, and comes back through Form 3800, Part IV in the year it is used.

• Instructions for Form 3800 (2025)
• Instructions for Form 6765 (Rev. December 2025)
• 26 U.S.C. § 38(c)
• 26 U.S.C. § 41(g)
• Instructions for Form 1120-S (2025)

• Form 6765Completing Form 6765, the credit form itself.
• Form 3800Where the research credit goes on Form 3800 and how it reaches the return.
• Form 1120-SS corporations: Schedule K line 13g, K-1 box 13 code M, and the shareholder.
• Form 1065Partnerships: Schedule K line 15f, K-1 box 15 code M, and the partner.
• Form 1040Individuals: Schedule 3 line 6a, Schedule C, and Form 1040-X.