Yes. Married filing separately (MFS) is not excluded from this deduction.
That surprises a lot of filers, because two other new 2025 deductions this portfolio has calculators for -- the "no tax on tips" / "no tax on overtime" deduction and the senior deduction -- both exclude MFS entirely. The auto loan interest deduction runs the opposite way: each spouse who files separately gets their own independent $10,000 cap.
Each MFS spouse tests their own modified adjusted gross income (MAGI) against the single-filer thresholds -- not the higher joint thresholds -- and claims the deduction on their own separate return:
| Item | MFS (per spouse) | Married filing jointly (combined) |
|---|---|---|
| Cap before phase-out | $10,000, on each spouse's own return | $10,000 total, shared by both spouses |
| Phase-out starts at MAGI | $100,000 (each spouse's own MAGI) | $200,000 (combined household MAGI) |
| Fully phased out at MAGI | $150,000 (each spouse's own MAGI) | $250,000 (combined household MAGI) |
| Reduction rate | $200 per $1,000 (or part) over the threshold | Same $200 per $1,000 (or part) over the threshold |
Two spouses, Spouse A and Spouse B, each finance their own eligible vehicle and each pay $8,000 of qualifying interest in the year. Their combined household MAGI is $240,000 either way -- only the filing status changes.
| Scenario | MAGI tested | Cap after phase-out | Deduction |
|---|---|---|---|
| Spouse A, filing MFS, MAGI $120,000 | $120,000 vs. single-filer $100k-$150k range | $10,000 − $4,000 = $6,000 | $6,000 |
| Spouse B, filing MFS, MAGI $120,000 | $120,000 vs. single-filer $100k-$150k range | $10,000 − $4,000 = $6,000 | $6,000 |
| MFS combined household deduction | $240,000 combined | — | $12,000 |
| Same couple, filing jointly, combined MAGI $240,000 | $240,000 vs. joint $200k-$250k range | $10,000 − $8,000 = $2,000 (one shared cap) | $2,000 |
At this specific combined income, filing separately produces a combined deduction six times larger than filing jointly -- because each MFS spouse's MAGI is tested against the lower, single-filer phase-out range independently, rather than the household's full combined MAGI being tested against the higher joint range all at once. Reverse the numbers -- one spouse earning most of the household income -- and the comparison can flip. There is no substitute for running your own numbers both ways.
Every other new-2025-deduction calculator in this portfolio treats MFS the same way: excluded entirely. This one does not, and that inconsistency is set by the statute itself, not by any pattern worth assuming holds across deductions:
| Deduction | MFS treatment |
|---|---|
| Auto loan interest (this page) | Eligible -- own $10,000 cap per spouse |
| No tax on tips / no tax on overtime | Excluded entirely |
| Senior deduction | Excluded entirely |
Yes. Unlike the separate 'no tax on tips' and 'no tax on overtime' deductions, which exclude MFS entirely, the auto loan interest deduction does not exclude MFS. Each spouse who files separately gets their own $10,000 cap on their own return.
The same $100,000-$150,000 MAGI range used for single filers and heads of household -- not the $200,000-$250,000 joint range. Each MFS spouse's own MAGI is tested against the single-filer thresholds independently.
Yes, in some cases. Two spouses each earning $120,000 MAGI (a combined $240,000) and each paying $8,000 of qualifying interest on their own vehicle loan can deduct $6,000 apiece filing MFS -- $12,000 combined. The same couple filing jointly, at the same $240,000 combined MAGI, shares one cap reduced to $2,000 total for the household -- a sixth of the MFS combined result.
Congress wrote each OBBBA deduction with its own filing-status rules; there is no single consistent MFS treatment across them. The 'no tax on tips' and 'no tax on overtime' deductions exclude MFS filers entirely. The senior deduction also excludes MFS. The auto loan interest deduction does not -- it is the one sibling calculator in this portfolio where an MFS filer is not automatically shut out.
Not necessarily. Filing status affects your entire return, not just this one deduction -- other credits, deductions, and tax brackets change with it too. This page and its calculator only show the auto loan interest math for each scenario; compare your full return both ways, or ask a qualified tax professional, before choosing a filing status because of this deduction alone.
The auto loan interest deduction calculator applies this same cap and phase-out logic to your own MAGI, interest paid, and filing status, and walks through the full eligibility checklist. Nothing you enter is uploaded.