The M-form: Filing Your Dutch Tax Return for the Year You Move
The M-form (migration-year tax return): why your first and last Dutch year is the trickiest one to file
The M in M-form stands for migration. It is the income tax return for the year in which you move to the Netherlands or leave it, the transitional year in which you are a resident taxpayer for part of the year and a non-resident for the other part. That split is exactly what makes the form notorious. Where an ordinary return covers one full year under one regime, the M-form has to process two periods of tax liability in a single return, ending in one assessment, and that is precisely where it tends to go wrong.
For most expats the M-form first appears in the year of arrival, and it is often worth real money: payroll tax is usually withheld as if you had lived in the Netherlands all year, while you were only resident for part of it, so the migration return frequently produces a refund. In the year of departure the form does the opposite work, gathering all the tax consequences of leaving into one document. This article explains what the M-form is, when you have to file it, how and by when, and where it goes wrong.
What is the M-form?
The M-form is the income tax return for the migration year, the year in which you immigrate to or emigrate from the Netherlands. In that year you are a resident of the Netherlands for part of the year, and therefore taxable on your worldwide income, and a non-resident for the other part, taxable at most on income from Dutch sources. The form combines both periods in a single return, after which one assessment follows. It is more involved than an ordinary return, with its own rules and its own pitfalls, which is why even experienced filers regard it as one of the hardest forms.
Do you file an M-form when moving to the Netherlands, or only when leaving?
Both. You file an M-form for the year you arrive and for the year you leave, because in each of those years your status changes partway through. In the full years in between, while you are resident, you file the ordinary resident return; once you have left and only Dutch-source income remains, you file the non-resident C-form. The migration year is the hinge, and it is the M-form that covers it.
Arriving with assets: the step-up that newcomers miss
For anyone arriving with wealth, the migration return is also where a valuable rule applies that many newcomers never hear about. From the day you settle in the Netherlands you are a resident taxpayer on your worldwide income, but you do not bring your full latent gains into the Dutch base. If you hold a substantial interest of five percent or more in a company, the acquisition price of those shares is, in principle, reset to their market value at the moment of immigration, so that only the increase in value after you arrive falls within the Dutch substantial-interest tax. This step-up is the mirror image of the exit tax imposed on people who leave, and having it documented correctly at the moment of arrival protects you from Dutch tax on gains that built up before you ever came. For a substantial interest in a Dutch company the rules are more specific and depend on any earlier Dutch tax liability, which is exactly the kind of detail to check before the move rather than after. Foreign income you continue to receive is generally shielded from double taxation by a treaty or by the unilateral relief rules, and once you have settled you may also qualify for Dutch allowances such as the healthcare allowance and should arrange a DigiD to deal with the tax authority online.
What makes the migration year so different?
Several rules behave differently in the migration year, and these cause most of the mistakes. Tax credits are granted only in proportion to time, and in full only for the resident period, so in a migration year you are not entitled to the whole amount, which visibly affects the outcome. From the moment you settle in the Netherlands you also become liable for national insurance contributions, for the state pension, long-term care and survivors' schemes, which the return reflects. In box 3 the deemed return is calculated in proportion to time, with parts of a calendar month left out, while the asset base is fixed on the reference date of 1 January even if you were still living abroad then; a limited base applies for the non-resident period and the full base for the resident period. Fiscal partnership covers only the period of resident liability, so income can be freely allocated between partners for that period alone, and only if it begins or ends at the same time for both; partners who immigrate together can, however, elect to be treated as partners for the whole year. The home needs attention in both directions: a former Dutch home can still count as a main residence for up to three years after departure while empty and for sale, and on arrival a home abroad may, depending on the circumstances, qualify as a main residence with the deductions that brings. Each of these is a point where intuition leads the filer astray.
How and when do you file the M-form?
For years from 2020 onward the M-form can be filed online through Mijn Belastingdienst using a DigiD, or an accepted European login key. If you cannot or prefer not to file online, you can request a paper M-form. For the migration year the online return can generally be filed from 1 May to 1 July of the following year, and if you request an extension before the deadline it usually moves to around 1 November. After emigration the tax authority normally sends a request to file, but the obligation can exist even without one, so the date on the assessment letter is the one to watch.
Where does it go wrong?
At the front end, things go wrong regularly. Some people do not receive the form automatically while they are nonetheless required to file, and so fall into default without knowing it. Others accidentally file an ordinary return in their first or last year instead of an M-form, which then has to be corrected. Anyone who registered only a year after arriving has to work out which year the form actually concerns. And if you expect a refund for the migration year, a provisional assessment can be requested rather than waiting a full year, while a running provisional refund or assessment often has to be stopped or adjusted after you move.
The departure year: exit tax and the loose ends
When you leave the Netherlands the M-form is more than a return; it is where the tax consequences of departure are recorded. If you emigrate holding a substantial interest in a company, a preserving assessment is imposed on the gain, and it has to land correctly in the form. The same goes for the treatment of the home, for accrued pension and annuity, and for the question of which part of your income and wealth is still attributed to the Dutch period. These are not routine entries, and an error can produce an assessment that only surfaces years later, or a missed deferral of payment that costs you money for no reason.
The international dimension
The M-form does not stand alone. It interacts with the tax treaty between the Netherlands and your other country, and with the way that country taxes the same year. What the Netherlands taxes or defers in the migration year has to line up with what the other country does, otherwise double taxation arises or a claim is left hanging unintentionally on one side of the border. The form is therefore the point where the Dutch arrival or departure and the foreign side have to fit together.
The corridor: migrating between the Netherlands and Suriname
For anyone migrating within the Netherlands–Suriname corridor the M-form gains an extra layer. The attribution of income to the Dutch and the Surinamese period, the treatment of a substantial interest in a Dutch or Surinamese company, and the interaction with the tax treaty between the two countries together decide how the migration year turns out. A home loan, a loan or wealth held across the border calls for a deliberate choice in the form about the right box and the right moment. Because the treaty and the Surinamese treatment depart from the standard case, the M-form here is part of a broader plan rather than a fill-in exercise.
Why you should not want to file this form alone
The M-form combines the hardest of two worlds: the complexity of a transitional year, with its different rules for tax credits, box 3 and partnership, and the weight of the tax consequences of migration. It has its own deadline, its own logic and a direct link to the tax treaty of your other country. The chance of an error, a missed deduction or a mishandled preserving assessment is real, and the consequences run for years. This is the form where good advice in advance is cheaper than repair afterwards.
That is how we approach it. We prepare the M-form as part of your full tax position in the migration year, with attention to the exit tax, the home, pension, the tax credits and box 3, and with the connection to the treaty, and with particular experience in the Netherlands–Suriname and Netherlands–Spain corridors. That way the form becomes not a risk but the closing piece that settles your move as it should.
This page is general information and does not constitute tax or legal advice. Amounts, dates and rules reflect the position at the time of writing and may change. For your specific situation we are glad to advise you personally.