What is the tax year?

Definition of the tax year

You earn your income during a calendar year, you declare it the following year, and the tax is assessed for that tax year. Tax amounts (tax-free amount, ceilings, reductions) are set per tax year or per income year: always check which of the two a figure refers to.

Companies also have a tax year, linked to the closing date of their accounts.

Worked example

Your 2026 salaries form tax year 2027: you declare them in the spring or summer of 2027, and the administration has until 30 June 2028 to send you the tax assessment notice (aanslagbiljet / avertissement-extrait de rôle). The tax-free amount of €11,550 is the one for ‘income 2026, tax year 2027’.

In Dutch: aanslagjaar

On a Dutch-language tax return, tax assessment notice (aanslagbiljet) or letter from the tax authorities, the tax year is called ‘aanslagjaar’ and the income year ‘inkomstenjaar’; on French-language ones, ‘exercice d’imposition’ and ‘année des revenus’. Also called assessment year in English.

Dutch term taken from: FPS Finance, Wolters Kluwer (Jef Wellens) (secondary source).

Not to be confused with…

• Taxable period: this is the income year itself (calendar year 2026), not the year in which the tax is calculated.

Related terms

• Personal income tax (PIT)Tax and tax return · in Dutch: personenbelasting
• Tax assessment noticeTax and tax return · in Dutch: aanslagbiljet