The credit exists for everyone the other one excludes. Graduate students, part-time students, people taking a single course, people retraining mid-career and people who have already used four years of the American Opportunity credit all land here. That is the useful way to hold the pair in mind, because the two are computed on one form, share one income phase-out and cannot both be claimed for the same student in the same year. Section 25A(c)(2)(A) is explicit that expenses of a student for whom the American Opportunity credit is allowed are not taken into account under this subsection, so a household with two students commonly claims one credit for each rather than choosing between them.
The expense definitions are not the same, and this is the second most confused point after per-student versus per-return. Both credits start from "qualified tuition and related expenses", meaning tuition and fees required for enrolment or attendance. Section 25A(f)(1)(D) then substitutes "tuition, fees, and course materials" for the American Opportunity credit only. Publication 970 draws the practical line: for this credit, fees and expenses count "only if the fees and expenses must be paid to the institution for enrollment or attendance", while required course materials count for the American Opportunity credit wherever they were bought. A textbook bought second-hand from a classmate is a qualifying expense for one credit and not the other. Neither credit reaches room and board, insurance or transport. A student activity fee sits in between: section 25A(f)(1)(C) excludes nonacademic fees, but Publication 970 treats one as qualifying where the institution requires it to be paid as a condition of enrolment or attendance. Neither credit reaches courses involving sports, games or hobbies unless they are part of a degree programme, and for this credit alone Publication 970 adds a second way out of that exclusion: a course taken to acquire or improve job skills.
One phase-out serves both credits, and it stopped being indexed in 2020. Section 25A(d)(1) reduces the credit ratably as modified adjusted gross income runs from $80,000 to $90,000, or from $160,000 to $180,000 on a joint return. Before 2021 this credit had its own separate and lower thresholds, which were inflation-adjusted under section 25A(h). The Consolidated Appropriations Act, 2021 struck the two separate income limitations and repealed section 25A(h) outright, leaving one unindexed phase-out for both credits from tax years beginning after 2020. That history is why sources dated 2020 or earlier give different numbers in good faith: they are stale rather than wrong for their time.
The other shared rules. Section 25A(g)(6) denies both credits to a married taxpayer who does not file jointly, whatever the income. Section 25A(g)(1), as rewritten by the 2025 tax law for tax years beginning after 2025, requires a Social Security number for the taxpayer and for the student where they differ, replacing the previous taxpayer identification number standard. Section 25A(g)(2) reduces qualifying expenses by tax-free scholarships and similar assistance before anything else is computed. Section 25A(g)(5) denies the credit for any expense that also produces a deduction. And section 25A(g)(8) conditions the credit on receiving the payee statement the institution files, which is Form 1098-T.
Nonrefundability is what limits it in practice. The credit sits in the nonrefundable subpart, so it is capped by the tax the household actually owes and nothing carries forward. A part-time student with modest earnings, which is the profile the credit is designed around, frequently owes little enough income tax that a $2,000 credit cannot be used in full. Where a household qualifies for both credits and can only use one for a given student, the American Opportunity credit is usually worth more for that reason as well as its larger maximum.