Your tax return: what the pre-filled form does not know
More than one taxpayer in two gets a simplified tax return proposal, and 93% accept it without changing a thing. That is usually the right call — except the tax office does not know everything. Childcare costs for a summer camp, a donation made without your national number, a custody arrangement that changed mid-year: those three slip through year after year. Here are the deadlines you cannot miss, and the boxes that deserve a second look.
Personal income tax is declared the year after the income was earned. The return you file in 2026 therefore covers your 2025 income: that is what is called assessment year 2026. Everything confusing about the Belgian system starts there, and most misread tax tables come down to mixing up those two years.
There is no single deadline, there are three
MyMinfin opened on 28 April 2026. From that point three deadlines run in parallel, depending on how you file and on what you declare.
| How you file | Deadline |
|---|---|
| Paper return | 30 June 2026 |
| Online, no specific income | 19 July 2026 |
| Online, with specific income | 16 October 2026 |
| Flat-rate taxpayers and farmers | 15 January 2027 |
FPS Finance announced 15 July at its April press conference, then published an official extension to 19 July 2026 inclusive. That later date is the one that counts.
Specific income — self-employed income, foreign professional income and a few other categories — automatically opens the October deadline. You do not have to apply for an extension: MyMinfin tells you itself whether it applies to you.
Two changes are worth noting. Agents, accountants included, now face the same deadlines as citizens: going through a professional no longer buys extra time. And an online return you have already submitted can be corrected once, up to 19 July.
The simplified proposal: three known blind spots
FPS Finance sent a simplified tax return proposal to 3,929,000 citizens, or 56% of taxpayers excluding the self-employed. Last year 93% accepted it without touching a thing.
That figure is mostly good news: in the vast majority of cases the tax office has the right data. But it publishes the list of what it does not know.
⚠️ An uncorrected proposal becomes your tax return. Doing nothing counts as acceptance. If you need to change something, your deadline is 30 June on paper and 19 July online — the same dates as for a standard return.
Tax bands and the tax-free allowance
Part of your income escapes tax entirely: that is the tax-free allowance. For 2025 income it stands at €10,910.
| Taxable income band | Rate |
|---|---|
| Up to €16,320 | 25% |
| €16,320 to €28,800 | 40% |
| €28,800 to €49,840 | 45% |
| Above €49,840 | 50% |
These rates apply band by band. Crossing a threshold never lowers your net pay: only the euros above the threshold are taxed at the higher rate. It is the most stubborn misunderstanding in Belgian tax, and it occasionally costs people a raise they turned down.
Increases for dependants
Every dependant raises the tax-free allowance, and the effect is not linear: going from two to three children is worth far more than going from one to two.
| Dependent children | Increase in the allowance |
|---|---|
| 1 child | €1,980 |
| 2 children | €5,110 |
| 3 children | €11,440 |
| 4 children | €18,510 |
| Per additional child | + €7,070 |
| Child under 3 (no childcare reduction claimed) | + €740 |
| Single parent with a dependent child | + €1,980 |
A severely disabled child counts as two. And to stay a dependant, the child must not exceed €12,000 in net resources — more on that below, because this ceiling has just changed in nature.
Professional expenses: the flat rate, and when it runs out
The statutory flat rate is applied automatically: you have nothing to claim and nothing to prove. It equals 30% of your gross taxable pay less your personal social contributions, and never goes above €5,930.
You hit that cap at around €20,000 of taxable pay after contributions. Beyond it the flat rate stops growing — that is the point where actual expenses become worth a look, especially if you clock up a lot of commuting kilometres. Actual expenses, though, mean keeping every receipt.
The benefits people forget
It is rarely the big ones that get missed. It is the quiet ones.
For long-term savings and personal group insurance contributions, the ceiling depends on your professional income through a formula the FPS does not publish as a fixed amount. We are not going to invent one: your 281.60 certificate and the MyMinfin simulator give the figure that applies to your situation.
The four changes in this tax return
The old table drew a distinction between a couple, a parent taxed separately, and a single parent with a disabled child. It is gone. One figure now applies: €12,000 in net resources for a child, whatever the parents' situation. If you come across a three-figure table somewhere with amounts around €4,000 to €7,000, it is out of date.
The form itself has slimmed down: 47 fewer federal codes, taking the total back below 700 — the lowest it has been in ten years.
If you are late
A late return, or no return at all, exposes you to a fine, a tax increase, or both. The tax office can also switch to an automatic assessment: it then works out your tax from whatever data it holds, and it is on you to prove the exact amount of your income. That reversal of the burden of proof is the real penalty.
Since 29 July 2025, though, a right to make a mistake applies. A first error made in good faith does not trigger an automatic increase. This is not a theoretical principle: out of 62,600 potential increases in the previous assessment year, 53,800 were not applied — close to nine cases in ten.
We do not publish a range for the fines: the scales sit in articles of the Income Tax Code that FPS Finance does not make available in any consultable form. The amount depends on how serious the breach is and whether it is a repeat.