What is the deduction cap?

Since 2020 the rate at which mortgage interest can be deducted is being lowered each year. It reached 37.05% in 2020 and settled at 36.97% for 2023 onward, even if your actual marginal rate is the top 49.5% band. This calculator applies that capped rate.

What is the eigenwoningforfait?

It is a notional rental value added to your box-1 income for owning your home (typically 0.35% of the WOZ value). You deduct interest but must add this forfait, so the net deduction is interest minus forfait.

Does the cap affect lower earners?

No. The cap only bites if your marginal rate is above the capped aftrek rate. If you sit in the lower box-1 bracket (around 36.97%), your deduction rate already equals the cap, so nothing is lost.

Is this only for the main home?

Yes. Hypotheekrenteaftrek applies to the eigen woning (your primary residence) financed with a qualifying annuity or linear mortgage. Interest on a second home or buy-to-let falls under box 3, not box 1, and is not deductible this way.

Is my data sent anywhere?

No. The whole calculation runs locally in your browser. None of your figures leave your device.

Netherlands Mortgage Interest Deduction Calculator

In the Netherlands, mortgage interest on your main home (eigen woning) is deductible from box-1 income, but the rate at which it can be deducted has been phased down since 2020. This free calculator applies the capped aftrek rate, nets off the eigenwoningforfait, and shows your real box-1 tax saving.

How it works

The deduction is not simply your interest times your marginal rate. Two adjustments apply:

net deductible = mortgage interest - eigenwoningforfait
tax saving     = net deductible x capped aftrek rate

The capped aftrek rate is the policy lever. Even top earners in the 49.5% band can only deduct at the capped rate, which settled at 36.97% for 2023 and later years. If your marginal rate is below the cap, your own (lower) marginal rate applies instead — the cap only reduces the benefit for high earners.

The eigenwoningforfait is a notional benefit of owning your home, added back to income (often around 0.35% of the WOZ value). Because it is added, it reduces the net amount on which you save tax.

Example

You paid EUR 12,000 of mortgage interest and your eigenwoningforfait is EUR 1,400 on a EUR 400,000 WOZ home. Net deductible = 12,000 − 1,400 = EUR 10,600. At the 2024 capped rate of 36.97%, your tax saving is 10,600 × 0.3697 = EUR 3,919. A top-band earner cannot claim 49.5% on this — the cap limits the benefit. Everything runs locally; nothing leaves your browser.