Tracking rental income for your Dutch tax return: what do you need?

Every spring the same question: which numbers does the tax return (or your adviser) actually need? For most private landlords in the Netherlands the property falls in Box 3, and then the list is surprisingly short — but you do need the figures at hand.

What Box 3 requires

Box 3 doesn't tax your actual rental income but a deemed return on your assets on 1 January (the reference date). You need:

1. WOZ value of the rented property (valuation date one year earlier). For tenanted properties the leegwaarderatio usually applies: a discount on the WOZ value depending on the annual rent relative to that value.
2. Outstanding mortgage debt on 1 January — debts reduce your taxable assets (above the debt threshold).
3. Annual base rent — needed to determine the leegwaarderatio.

That's the legal core. But don't stop there.

Why you should still track everything

• Actual-return relief. The Box 3 debate keeps evolving: landlords who can prove their actual return was lower than the deemed return may benefit — but only with a complete record of rent, costs and value development.
• Box 1 risk. If you put significant labour into the rental (high-touch short-term letting, development), the tax authority can argue the result belongs in Box 1 — and then actual income and expenses suddenly do count.
• Sale. You'll need purchase costs and renovations for your return-on-investment and in any dispute.

The practical checklist

Per property, per year:

• base rent per month + dates received;
• service-charge advances and the annual settlement (separately);
• the WOZ decision letter;
• mortgage: balance on 1 January and interest paid;
• every cost with its receipt: maintenance, VvE, insurance, municipal taxes, energy;
• for short-term rentals: booking statements, platform fees and tourist tax.

How Lentano solves this

In Lentano these figures are simply there if you track them during the year: monthly rent payments, transactions per category (with receipts), mortgage data and WOZ value per property. The Box 3 overview computes the deemed return, and the accountant export is one click.

Note: general information, not tax advice. Box 3 rules are in flux — verify with the Belastingdienst or your adviser.