For the Mortgage Interest Tax Credit, interest is the starting point—not the full monthly repayment. A useful claim file separates the tax year, the lender's interest certificates and the comparison-year evidence. The 2026 calculation must not be copied unchanged from a 2025 example.
Compare the right years
Revenue's current guidance covers 2023 through 2026. For 2023–2025, relief is at 20% of the qualifying increase over 2022, subject to the applicable conditions and a maximum EUR 1,250 per residence each year. For 2026, only 50% of the qualifying increase over 2022 enters the 20% relief calculation, with a maximum credit of EUR 625 per residence.
A worked example with the same interest increase
Assume a qualifying full-year loan, sufficient Income Tax liability and fictional annual interest of EUR 13,000 in the claim year compared with EUR 9,000 in 2022. The increase is EUR 4,000. Under the 2025 calculation, 20% gives EUR 800. Under the 2026 calculation, EUR 4,000 multiplied by 50%, then by 20%, gives EUR 400. The unchanged increase therefore does not produce an unchanged credit.
This illustration does not decide whether a loan qualifies. Partial-year loans and more than one claimant need their own treatment. Revenue's system calculates the relief after the required information is entered, so use the official result rather than a spreadsheet as the final claim figure.
Gather evidence before opening the return
- Confirm the relevant claim year.
- Keep the 2022 interest information and the claim-year certificate together.
- Separate interest from capital repayments, fees and the total bank debit.
- Locate the mortgage-balance evidence required by the qualifying conditions.
- Identify other claimants and ask how the residence-level limit applies.
If a certificate is missing, ask the lender how to obtain it. If a figure appears inconsistent with another record, resolve the difference before entering a replacement amount. Keep a note of what each document supports; two similar numbers from different periods are not interchangeable.
The credit and the mortgage payment are different things
The credit offsets Income Tax, not USC or PRSI, and available Income Tax liability can limit the benefit. It does not change the repayment specified in your mortgage contract. Put the confirmed tax result in the tax section of a household budget rather than reducing the recurring loan payment by an assumed permanent refund.
For a joint claim, keep the calculation and allocation together so a residence-level limit is not counted twice. Check Revenue's qualifying, partial-year and multiple-claimant guidance before submitting. The right next action is a complete evidence file for the selected year, not an estimate carried forward from a previous return.