Hypotheekrenteaftrek Explained: The 37.56% Cap and Eigenwoningforfait

It's the ability to deduct mortgage interest paid on your primary residence (eigen woning) from your Box 1 taxable income. It's genuinely one of the most consequential tax breaks for Dutch homeowners, but it comes with two things that trip people up: a deduction rate cap, and a separate, mandatory addition to income (the eigenwoningforfait) that has to be netted against the interest first.

Only partially. Mortgage interest is deductible at a maximum rate of 37.56% for 2026, matching the top of Box 1's second tax band, even if your actual top marginal rate is the higher 49.50% band. If your top marginal rate is 35.75% (the first band), you deduct at that lower 35.75% rate instead, since it's already below the cap, the cap only actually bites once your income reaches the second or third Box 1 band.

The eigenwoningforfait (EWF) is a notional rental value added TO your taxable income for owning a home, based on its WOZ (municipal valuation) value, 0.35% of WOZ value for homes valued €75,000-€1,350,000 in 2026, rising to 2.35% on the excess above €1,350,000 (the 'villabelasting' band). It exists because owning your home outright is treated as a form of income (you're not paying rent), and it's added at your actual marginal rate, not the capped 37.56% rate, only the interest deduction itself is capped.

Only partially, and the net direction depends on which is larger. If your mortgage interest exceeds your EWF, as is typical for anyone with a substantial outstanding mortgage, the difference is deductible at the capped rate. On a €450,000 WOZ value home with €12,000 in annual interest, the €1,575 EWF nets against the interest for a €10,425 deductible amount, worth €3,916 in tax savings for someone in the 49.50% band (capped at 37.56%). But if your EWF exceeds your interest, common for a low or near-paid-off mortgage, the shortfall is ADDED to your taxable income instead, at your full marginal rate, with no cap. On a nearly-paid-off €500,000 WOZ home with only €1,000 in remaining interest, the EWF of €1,750 exceeds it, adding €750 to taxable income and costing roughly €371 a year rather than saving anything.

Wet Hillen partially shields long-time homeowners with little or no mortgage from the EWF addition once their interest deduction has dropped below their EWF, phasing in the addition rather than applying it in full immediately. This calculator does not model Wet Hillen (flagged deliberately as out of scope), so a near-zero-mortgage scenario's actual tax effect will be somewhat less negative than the raw EWF-minus-interest calculation shown here suggests.

From your salary income alone, run through the standard Box 1 bands (35.75% up to the first threshold, 37.56% for the second band, 49.50% above that), the same bands used in the standard Netherlands take-home calculator. This is a simplification used by most comparable Dutch mortgage-deduction calculators, it's accurate unless the eigen-woning adjustment itself is large enough to push your income across a band boundary, an edge case this calculator doesn't separately re-run.

Not directly, the 30% ruling changes how much of your salary is taxable in the first place, our 30% ruling explainer covers that mechanic, but it doesn't change the mortgage interest deduction rules themselves. It can indirectly shift which Box 1 band your taxable salary falls into though, which is what determines your marginal rate for this calculation, worth running both calculators together if the ruling applies to you.