How is the deductible interest charge prorated?

For the 2024 tax year:

No prorata calculation is made for the 2024 tax year.

For the 2023 tax year:

The calculation of deductible interest expense is based on a number of factors, including :

• the date of acquisition of the property
• the date on which you moved into the property
• the interest paid on the mortgage
• the interest ceiling.

Here are 2 examples:

A couple (married or civil union) bought a house on 01/04/2023 and moved in on 01/07/2023.
They paid interest of €10'000 in 2023.
The ceiling to be applied is €6'000.
Non-occupancy period: 91 days
Days to end of year: 275

Calculation details :

Field 1017: __
10'000 * (91 / 275) = 3'309,09€

Field 1021: __
10'000 - 3'309,09 = 6'690,91€
As the €6'690.91 is greater than the €6'000 ceiling, the ceiling must be applied.

Field 1029: __
3'309,09 + 6'000 = 9'309,09€

A single person bought a house on 01/04/2023 and moved in on 01/07/2023.
He paid interest of €5'000 in 2023.
The ceiling to be applied is €3'000.

Non-occupancy period: 91 days
Days to end of year: 275

Calculation details :

Field 1017: __
5'000 * (91 / 275) = 1’654,55€

Field 1021: __
5'000 - 1’654,55€ = 3'345,45€
As the 3'345,45€ is greater than the €3'000 ceiling, the ceiling must be applied.

Field 1029: __
1’654,55 + 3'000 = 4'654,55€

Updated on: 11/02/2025