Car Loan Interest Deduction Calculator

How the car loan interest deduction is calculated

Six gates, then a cap, then a phase-out that is twice as steep as anything else in this package. The vehicle must be new with you as its original user, its final assembly must have occurred in the United States, it must weigh under 14,000 lb gross, and it must be for personal use. The financing must be a loan rather than a lease, secured by a first lien on the vehicle itself, originated after 31 December 2024. Fail one and the deduction is zero.

Clear all six and you deduct the interest you actually paid, up to $10,000 for the return — not per vehicle and not doubled for a joint return. The phase-out then removes $200 for every $1,000 of MAGI above $100,000 ($200,000 joint), which closes the whole thing over a $50,000 band rather than the $250,000 band tips and overtime get.

ceiling = $10,000 (per return; no joint doubling) excess = max(0, MAGI − threshold) threshold: $100,000 single/HOH, $200,000 joint increments = excess ÷ 1,000, ROUNDED UP ("or portion thereof") reduction = increments × $200 (20% of the excess) your ceiling = max(0, $10,000 − reduction) deduction = min(interest paid, your ceiling) ceiling reaches $0 at $149,001 single/HOH $249,001 joint — the round-up kills it a thousand dollars early tax saved = tax(taxable income) − tax(taxable income − deduction)

interest paid

Interest paid on the qualifying loan during the tax year — your lender reports it on Form 1098-VLI; this page estimates it by amortizing the amount financed at your APR and term

MAGI

AGI plus any foreign-earned-income exclusions — the threshold is the lowest in the package — $100,000 rather than $150,000

increments

Whole thousands of MAGI above the threshold, rounded UP — the statute says "for each $1,000 (or portion thereof)", which is the opposite of the rounding tips and overtime use

your ceiling

The $10,000 cap after the phase-out — at $200 per $1,000 this falls twice as fast as the tips ceiling

first lien

The lender's security interest ranks first against the vehicle — dealer and bank auto loans normally qualify; unsecured personal loans, home equity borrowing and leases do not

The rounding detail is worth pausing on because it runs the other way from the rest of this package. Tips and overtime round the $1,000 increments down, which favours the taxpayer; §163(h)(4) says "or portion thereof", so a single dollar past a thousand-mark counts as a whole increment. The practical effect is that the ceiling reaches zero at $149,001 rather than $150,000 — small, but it is why we model the rounding explicitly rather than treating the phase-out as a smooth 20%.

Note also what this deduction is not: it is not a credit, and it is not the clean-vehicle credit it is sometimes confused with. It reduces taxable income, so its value is your marginal rate — roughly a fifth to a quarter of the interest for most buyers. Anyone choosing a vehicle partly on this basis should size it against the depreciation on the same vehicle, which the car depreciation calculator puts in the thousands per year.

Worked examples

Frequently asked questions

What this car loan interest calculator doesn't handle

It estimates one year of interest on one loan and asks you to self-certify six legal tests. Each of those is a place where the return can diverge from this page.

• Interest is estimated, not reported — The figure comes from amortizing the amount financed at the APR and term you entered, over the first twelve months. A real loan has an origination date mid-year, possible fees rolled into the balance, and a payment schedule that may not start immediately — so the first calendar year's interest is usually less than a full twelve months. Your Form 1098-VLI is the authority.
• Only the first year — Interest on an amortizing loan falls every year. This page shows year one, which is the largest. Over a 72-month loan the deduction roughly halves by year four, and the provision expires after 2028 in any case — so a loan taken out in 2026 gets three deductible years out of six.
• The eligibility tests are self-certified — The six checkboxes are taken at face value. In particular the calculator cannot verify final assembly, which is the test buyers most often get wrong, and it does not ask for the VIN that the return requires. Tick the boxes honestly or the number is fiction.
• One vehicle, one loan — The $10,000 cap is per return, so a household with two qualifying loans shares it. This page models a single loan, and the form defers the multiple-VIN case to the Schedule 1-A instructions.
• Business and mixed use — Personal use only. A vehicle used partly for business falls outside this model entirely — the business share of the interest may be deductible on a different schedule under different rules, and neither this page nor Schedule 1-A Part IV handles the apportionment.
• State tax — Federal income tax only. States that levy an income tax generally do not conform to a new federal deduction unless they legislate for it, so assume the state treatment of your car loan interest is unchanged.