Mortgage Interest Split Calculator: Divide the 1098 Between Co-owners
Two people, one Form 1098. See what each co-owner deducts — interest and property taxes — and where it goes on the return.
When two people co-own a house, each can generally deduct the mortgage interest they actually paid — the owner named on the Form 1098 reports their share on Schedule A line 8a, and the other reports theirs on line 8b with a statement, as long as the shares total no more than the 1098 amount.
Last updated August 2026
Every January the lender sends one Form 1098 — to one owner — no matter how many people actually paid the mortgage. If you co-own with a partner, friend or family member, the IRS still lets each of you deduct the share of the interest you actually paid. This calculator splits the interest (and property taxes) by what each owner paid, so each person knows the number that goes on their return.
It's built for the situations the 1098 handles worst: unmarried couples, co-owning friends, parents on the loan with a child, and married couples filing separately.
How this calculator works
- Enter the mortgage interest from box 1 of the Form 1098, the property taxes you paid (optional), and each owner's share of the payments — 50/50 if you paid from a joint account you fund equally, or whatever your actual split was.
- Each owner's deduction is the total times their payment share, reconciled to the cent so the shares add up to exactly the 1098 amount — the IRS's core rule is that the combined deductions can't exceed what the lender reported.
- You must be an owner AND have actually paid to deduct. Paying interest on a house you don't own, or owning a house someone else paid for, generally gets you nothing.
A worked example: one 1098, two returns
Jordan and Riley co-own a house as an unmarried couple. The 1098 arrives in Jordan's name showing $18,000 of interest, and the county collected $6,000 in property taxes. They split every payment 50/50, so each deducts $9,000 of interest and $3,000 of property taxes (subject to the SALT cap).
Jordan — the name on the 1098 — reports $9,000 on Schedule A line 8a. Riley reports $9,000 on line 8b ('home mortgage interest not reported on Form 1098') and attaches a statement with Jordan's name and address explaining the 1098 arrived under Jordan's name. Same house, same form, two clean returns.
Australia and the United States
The math is the same wherever you buy. For country-specific tax and legal detail — stamp duty and CGT in Australia, closing costs and capital gains in the US — read the guide for Australia or the United States.
Good to know
- Splits by the payment shares you enter — the IRS position is that each co-owner deducts what they really paid, so keep records that back your split.
- Property taxes are subject to the SALT deduction cap, and mortgage interest to the acquisition-debt limit; this tool splits the amounts, it does not apply those caps.
- US federal rules only. In Australia, interest on your own home is not deductible (investment properties differ) — see the Australian guide.
- Educational estimate — not tax advice. Confirm your filing with a CPA or tax professional.
Frequently asked questions
Can two people claim the same house on their taxes?
Yes — co-owners each claim the share of the mortgage interest and property taxes they paid. What they can't do is both claim the full amount: across all returns the deductions can't exceed what was really paid, and the interest total can't exceed the Form 1098.
How do we split one Form 1098 between two people?
The owner named on the 1098 deducts their share on Schedule A line 8a. The other owner deducts theirs on line 8b and attaches a statement naming the person who received the 1098 (with their address) and explaining the split. Both keep records of who paid what.
Who claims the mortgage interest if we file separately?
Married filing separately, each spouse deducts the interest they paid — commonly half each if the mortgage came from joint funds. One spouse can't take the whole deduction unless they actually made the payments (and both must either itemize or both take the standard deduction).
Can one of us claim all the interest if they made all the payments?
Generally yes — the co-owner who paid all the interest from their own funds can deduct all of it, provided they're an owner and liable on (or an equitable owner of) the home. The other owner then deducts nothing. The deduction follows the money, not the headcount.
What if my name is on the loan but not the title, or on the title but not the loan?
To deduct, the IRS wants you to be an owner (legal or equitable) with an obligation to pay. On the loan but never on the title is the weak spot — a co-signer who doesn't own and doesn't live there usually can't deduct. On the title but not the loan can still work if you actually make payments on a debt secured by your home.
Do unmarried couples get one mortgage-interest limit or two?
The acquisition-debt limit ($750,000 for loans after December 2017) applies per taxpayer for unmarried co-owners — a real quirk of the rules that can favor buying unmarried at high price points. Most co-owners are nowhere near the cap, but if you are, get professional advice.