Is the deadline 1 May or 30 April?

The Belastingdienst says your return must be in before 1 May, so in practice the last day is 30 April 2027. Your filing letter states the exact date that applies to you. If it gives a different date, follow the letter.

Do I pay interest if I have an extension?

Yes, if you end up owing tax. Tax interest is charged when your return arrives on or after 1 May, and it runs from 1 July. An extension gives you more time to file but does not switch off the interest. In 2026 the rate for income tax is 5% a year.

I arrived in the Netherlands in 2026. Do I still file before 1 May?

No. For the year you arrived or left, you file the M return, which works to a different timetable. For 2025 it was available online from 1 May 2026 and had to be filed by 1 July 2026, and the same pattern is expected in 2027. Check the date in your letter.

Your 2026 tax return: the 1 May 2027 deadline and extensions

If you get a letter asking you to file your Dutch income tax return for 2026, it has to reach the Belastingdienst (the Dutch Tax Administration) before 1 May 2027, unless the letter gives a different date. Filing opens in early March: in 2026 the season started on 1 March, and the same pattern is expected in 2027. File before 1 April and the Belastingdienst promises you will hear back before 1 July. If you need more time, ask for an extension before 1 May and you get until 1 September.

The Belastingdienst had not yet published its 2027 filing calendar when this guide was checked. The dates below follow the standing rules and the pattern it used for the 2025 return in 2026. Check the letter you receive: the date in it is the one that counts.

The dates at a glance

What	2026 return (filed in 2027)	Status
Filing opens	Early March 2027 (1 March in 2026)	Expected, based on 2026
Deadline with a filing letter	Before 1 May 2027, or the date in your letter	Standing rule
Hear back before 1 July if you file by	Before 1 April 2027	Standing promise, confirmed for 2026
Deadline after an extension	1 September 2027	Standing rule
M return (year you arrived or left)	Online from 1 May, deadline 1 July 2027	Expected, based on 2026
No letter, but you owe tax	Before 14 July 2027	Standing rule

Who has to file

The trigger is the aangiftebrief (filing letter). If you got one, you must file before the date in it, which is often 1 May. That applies even if you think you owe nothing.

If you didn't get a letter but you know you will have to pay, you still have to file. The Belastingdienst's rule is to send it before 14 July of the year after the tax year, so before 14 July 2027 for 2026.

If you expect money back and didn't get a letter, filing is voluntary. You can go back 5 years: in 2027 you can still file for 2022.

File before 1 April, hear before 1 July

The Belastingdienst's standing promise is simple: file before 1 April and you get a response before 1 July. It repeated this for the 2025 return in its press release of 1 March 2026. If you file after 1 April, it tries to reply within 3 months.

The response is usually a voorlopige aanslag (provisional assessment) or a definitive assessment. The legal time limit is much longer: the Belastingdienst has 3 years after the end of the tax year to send the final assessment. For 2026 that means by 31 December 2029, plus the length of any extension you had.

If you expect a refund, filing early is the simplest way to get it sooner.

Asking for an extension

You can ask for uitstel (an extension) online in Mijn Belastingdienst, the Belastingdienst's personal portal, which you log in to with DigiD. The rules:

Ask before 1 May.
You can only use the online request if you received a filing letter.
Your fiscal partner has to ask separately.
The online form covers your first extension only.
The extension runs until 1 September.

An extension doesn't stop tax interest (see below). If you are likely to owe money, filing on time is cheaper than filing late with an extension.

The M return for the year you arrived or left

If you moved to the Netherlands or left it during 2026, you don't file the normal return for that year. You file the M-aangifte (M return, M for migration), which covers the part of the year you lived here and the part you didn't. Our guide to the M-form explained goes through it in detail.

The timing is different. For the 2025 year, the online M return was only available in Mijn Belastingdienst from 1 May 2026, and the deadline was 1 July 2026. The paper form could be ordered from 1 April and was sent from 1 May. Expect the same pattern in 2027. The 1 April promise doesn't apply. The Belastingdienst says you usually hear within 3 months of filing an M return.

What happens if you file late

The Belastingdienst doesn't fine you the day after the deadline. If your return is missing, you get a formal demand called an aanmaning with a new deadline. Filing late, for the fine, means filing after the deadline in that demand. Then you can get a verzuimboete (penalty for failing to file):

€469 if you don't file an income tax return, or don't file it on time
up to €6,709 if you fail to file repeatedly

The Belastingdienst doesn't impose the fine if you were not at fault in any way. If you don't file at all, it also makes an estimate of your income and taxes you on that. Correcting an estimate afterwards is more work than filing in the first place.

Tax interest

Belastingrente (tax interest) is separate from the fine. You pay it on the tax you owe if the Belastingdienst receives your return on or after 1 May of the year after the tax year, or if it changes your figures. It runs from 1 July. From 1 January 2026 the rate for income tax is 5% a year. The rate for 2027 was not yet known when this guide was checked.

You avoid it by filing before 1 May, provided the Belastingdienst accepts your figures unchanged. An extension to 1 September doesn't protect you from interest.

Provisional assessments

A voorlopige aanslag is an estimate of the income tax you will pay or get back. It can arrive at two points.

At the start of the year. You can ask for one so that you pay or receive a monthly amount during the year, rather than a lump sum after you file. That is useful if you expect a large refund, for example from a deduction, or a large bill. The Belastingdienst can also send you one without you asking, if it expects you to owe a lot. You request or change it in Mijn Belastingdienst.

After you file. You may get a provisional assessment based on your return first, and the definitive assessment later.

Either way, the amounts are settled when your final assessment for the year is made. If your situation changes during the year (a new job, a pay rise, the end of the 30% ruling, a move abroad), change your provisional assessment straight away. Otherwise you may face a large bill after you file.

Where to go from here

A return with one employer and a rented home is usually straightforward, and much of it is pre-filled. If you have a partial year, foreign income, assets abroad or a ruling that started or ended in 2026, it is worth having someone check it. You can request tax advice from an adviser who works in English. If 2026 was the year you arrived or left, read the M-form explained first.

Sources

Figures checked against the sources above on 23 September 2026.

Photo: Wikifrits, Wikimedia Commons, Public domain.