In short: In the Netherlands you file the income tax return for a tax year in the following year. For tax year 2025 you can file from 1 March 2026 via Mijn Belastingdienst or the app (log in with DigiD). The standard deadline is before 1 May 2026. If you file before 1 April, you usually receive a response before 1 July. Much of the data — wages, bank, mortgage, WOZ — is pre-filled, but you must check it yourself. If you cannot meet 1 May, request an extension in time. This is general guidance, not tax advice; when in doubt consult the official source or an adviser. (As of 2026.)
Filing taxes in the Netherlands: understanding the income tax return
Each year the Dutch tax office (Belastingdienst) asks you to file an income tax return. For most people this has become simpler over the years: much of the form is already pre-filled. Still, it pays to understand what happens — so you avoid an extra assessment and do not miss a refund. This chapter calmly explains how the return for tax year 2025 works, which deadlines apply (as of 2026) and where to start.
Gather your documents: annual income statement(s) from your employer or benefit, bank statements, mortgage and WOZ (property value) details, and proof of deductions such as gifts or medical costs.
From 1 March, log in to Mijn Belastingdienst (mijn.belastingdienst.nl) or the app using your DigiD — ideally the DigiD app with ID check.
Open the pre-filled return and check every section: wages, bank data, mortgage and WOZ value. Correct or add anything that is missing.
Submit before 1 May 2026. If you cannot make it, request an extension (uitstel) before 1 May — you usually then get until 1 September.
What matters
The income tax return is the yearly moment when you show the Belastingdienst what you earned and which deductions you had. Based on that, it is calculated whether you owe more tax or get money back.
For most private individuals it works like this: from 1 March the pre-filled return is ready in Mijn Belastingdienst (mijn.belastingdienst.nl) and in the app. You log in with DigiD — preferably the DigiD app with ID check for a higher assurance level. The Belastingdienst has then already entered much of your data: your wages or benefit, bank details, mortgage information and the WOZ value of your home.
That pre-filled data is a tool, not a final answer. You remain responsible for a correct and complete return. So check everything, because banks, employers and institutions can make mistakes. Deductions such as gifts, certain medical costs or study costs are usually not included automatically — you add those yourself.
The standard deadline for tax year 2025 is before 1 May 2026. Those who file before 1 April usually receive a response before 1 July. If you cannot make 1 May, request an extension in time; you then usually get until 1 September. Note: this chapter offers general guidance and is explicitly not tax advice. For a complex situation — your own business, foreign income, an inheritance — it is worth consulting the official source or engaging an adviser.
ExampleExample (rounded, for illustration): say your employer withheld payroll tax all year, but you made a deductible gift of 600 EUR that was not pre-filled. By entering that gift in your return, your taxable income drops by 600 EUR. At a marginal rate of around 36%, that saves about 600 x 0.36 = around 215 EUR in tax — money you receive back as a refund. (Amounts and rates are rounded and illustrative, as of 2026; when in doubt check the official source.)
Start early and keep your documents at hand. Use Kontoo to keep your income, fixed costs and savings organised throughout the year — so your figures are ready when filing opens. You file the official return via the Belastingdienst at mijn.belastingdienst.nl.
In depth
Extension and its consequences
If you request an extension before 1 May, you usually get until 1 September. An extension also shifts the final date by which you can request or change a provisional assessment (voorlopige aanslag). Keep in mind that tax interest (belastingrente) can accrue on an amount you pay later — so an extension is not automatically free of cost.
Provisional versus final assessment
After your return, a (provisional) assessment often comes first, followed by the final assessment (definitieve aanslag). If you get money back, it is transferred around the date on the assessment. In exceptional cases the final assessment can arrive years later, but in practice it usually comes within a few months.
Guidance, not advice
This chapter is meant to orient you, not to serve as tax or legal advice. Rules, rates and thresholds change every year. For your specific situation, the official information from the Belastingdienst or the judgment of a qualified adviser always applies.
Checklist
I know that filing for 2025 opens on 1 March 2026 and the standard deadline is before 1 May 2026.
I know that I log in to Mijn Belastingdienst with DigiD.
I understand that I must check the pre-filled data myself and can add deductions.
I know that I can request an extension before 1 May if I miss the deadline.
Common myths
Myth: The pre-filled return is always correct, so I only need to click submit.
Reality: The data is a starting point, not the truth. Employers and banks can make mistakes and deductions are often missing. You remain responsible; submitting unchecked can lead to an extra assessment or a missed refund.
Myth: If I do not receive a letter, I do not need to file.
Reality: Even without an invitation you may be required to file — for example if you owe additional tax. And even when it is not mandatory, filing can pay off when you get money back. If in doubt, check your situation with the Belastingdienst.
Frequently asked questions
When must I file my 2025 return?
The standard deadline is before 1 May 2026. Filing opens on 1 March 2026. If you file before 1 April, the Belastingdienst usually responds before 1 July. (As of 2026; check the official source if in doubt.)
Do I still need to check the pre-filled return?
Yes. Employers, banks and institutions can make mistakes, and not all deductions are included automatically. Check your wages, bank data, mortgage and WOZ value, and add deductions yourself. Leaving an error can lead to an extra assessment or a missed refund.
What if I miss the deadline?
Request an extension before 1 May via the Belastingdienst. You usually then get until 1 September. Filing late without an extension can result in a penalty for non-compliance. (As of 2026.)
