Mortgage interest: what you can actually deduct

Interest on a housing loan cuts your tax base only for the home you live in. On a rented unit the same interest is worth more, but it goes somewhere else entirely.

Deadline: With your income tax return

Claimed for the previous year. The bank's interest certificate arrives in January or February.

Open the mortgage calculator

When interest is deductible

The deduction under §15 is tied to own housing: the property has to serve the permanent home of you or your close family. Being on the loan is not enough on its own.

The property serves your own housing, or that of a spouse, child, parent or grandparent.
You are a party to the loan and you own the property being financed.
The loan financed the acquisition, construction or settlement of a housing need, not a consumer loan secured by the flat.

How much comes off

How much comes off depends on when the loan was concluded, and the cap is a household one rather than per person.

Loans concluded from 1 January 2021: up to 150 000 CZK of interest a year.
Households still paying off pre-2021 loans keep the older 300 000 CZK cap.
If the loan or the own-housing use only lasted part of the year, the cap is pro-rated by twelfths.

A rented unit is a different rule

Interest on a property you rent out is not a §15 deduction. It is a real expense of the rental itself, which usually makes it worth more.

On a unit rented under §9, interest belongs to real expenses together with depreciation, repairs and insurance.
As a rental expense the interest is not capped at 150 000 CZK and reduces the rental base in full.
Choosing the 30 % flat expenses for §9 gives up interest, depreciation and every other real cost at once.

What you have to show

The deduction is claimed in the return and supported by documents you keep. The bank supplies the main one without being asked.

The bank's annual certificate of interest paid, which arrives in January or February.
Evidence that the property serves permanent housing, typically the address of residence.
Nothing at all in paušální daň: the flat payment cannot be reduced, so the deduction is lost for that year.

Common questions

Does refinancing reset my cap?

It can. A refinancing loan concluded from 2021 falls under the 150 000 CZK cap even where the original loan was older, because the higher cap belongs to the original contract.

I live in the flat and rent out one room. What then?

You split the interest. The share matching the rented part is a real expense of the §9 rental, the rest stays a §15 deduction for own housing, and the split has to follow something defensible such as floor area.

Can my spouse and I each deduct the full cap?

No. The cap belongs to the household, so the interest is either claimed by one of you in full or split between you up to the same total.

Know the interest before the certificate arrives

The mortgage calculator shows the monthly payment, the total interest and the overpayment for any Czech mortgage, so you can see what the deduction is worth.