Correcting your income tax return after you have filed it
Written by Ilias Aarrass7 min read · Published on · Last reviewed on 
In short
As long as there is no final assessment you correct your income tax return by refiling it; after that you object within 6 weeks of the assessment date, and once that period has passed you request an official reduction up to 5 years after the tax year.
- A provisional assessment does not prevent you from refiling; the last version counts.
- You can object up to 6 weeks after the date of the final assessment, not from the day you open the letter.
- A request for an official reduction only works if you paid too much and must be received within 5 years after the tax year.
- If the correction means you owe more, tax interest runs from 1 July following the tax year.
You have filed your income tax return and only then notice that something is off: an invoice you forgot, a deduction you left unused, or an amount in the wrong box. That is not a disaster, and certainly no reason to wait until the tax authorities find it themselves. There are three ways to put a return right, and which one you need depends on a single question: is there already a final assessment? This article explains what to do in each situation, which deadlines apply and what a correction can cost you in tax interest.
No final assessment yet? File a corrected return
As long as you have not received a final assessment, correcting is simple: you reopen your return in the tax portal, adjust the amounts and file it again. The last version counts. You do not need to write a letter, file an objection or add an explanation. A provisional assessment is no problem either: it is simply settled against the final assessment later.
If you are an entrepreneur, the corrected return is also where you fix the profit annex: your balance sheet, your profit and loss account and the entrepreneur's deductions that depend on it. There is no point in changing one wrong figure and leaving the rest, because the return has to add up as a whole. See also the step-by-step guide to the income tax return.
- Log in to the tax portal and open the return for the year in question.
- Adjust the incorrect amounts and then walk through the screens that depend on them, such as the entrepreneur's deductions.
- Check that the new result matches your annual figures and your time records.
- File the return again and keep the new confirmation of receipt with your records.
Final assessment already in? Object within 6 weeks
Once the final assessment has been issued, you can no longer simply refile the return. Then an objection is the route to take. You have six weeks from the date of the assessment, meaning the date printed at the top of the letter and not the day you opened it. You object digitally in the tax portal or by letter stating which assessment you object to, why, and what amount you believe is correct.
Objecting sounds heavier than it is. You do not need a conflict: a forgotten deduction or a typo is a perfectly good reason. Add the supporting documents straight away, so the invoice, the bank statement or the calculation involved. The more complete your objection, the faster it is handled. Read more in objecting to a tax assessment.
| Situation | What you do | Deadline |
|---|---|---|
| No final assessment yet | file the return again | no fixed deadline |
| Final assessment received | file an objection | 6 weeks from the date of issue |
| Objection period expired | request an official reduction | up to 5 years after the tax year |
| Error in your VAT return | [a supplementary return](kb:btw-suppletie-indienen) or a correction in the next return | as soon as you know |
Objection period passed: the request for an official reduction
If you only discover the error once the six weeks have passed, there is still a safety net: the request for an official reduction. With it you ask the tax authorities to lower the assessment after all. The request must reach them within five years after the end of the year the assessment relates to. So for your 2026 return you can still submit a request until the end of 2031.
Note the difference with an objection. If an objection is rejected you can go to court; if a request for an official reduction is rejected your options are narrower. The request also only applies when you paid too much, not when you paid too little. If you find out you declared too little, simply report it yourself: voluntary correction often prevents a deliberate-error penalty. See administrative and deliberate-error penalties.
What a correction costs: tax interest
If your correction means you have to pay more, the tax authorities may charge tax interest. That interest starts running from 1 July following the tax year. The later you correct, the longer the meter runs. If you are correcting because money is coming back to you, there is no interest disadvantage: you get the overpayment back, sometimes with interest compensation if the tax authorities took too long themselves.
That makes speed valuable. If in March you see that last year's return is wrong, correct it straight away rather than waiting for the assessment. You can also have your provisional assessment adjusted so you pay early and the interest period stays short. Avoiding tax interest explains exactly how that works.
A forgotten invoice of € 4,000
- Situation
- you forgot to include a sales invoice of € 4,000 in your turnover
- Income tax effect
- your profit rises by € 4,000, so you still owe tax on that amount
- VAT effect
- the VAT on that invoice must also be declared, through a correction or supplementary return
- What you do
- a corrected return or objection for income tax, plus a VAT correction
Result: By reporting it yourself, it stays at paying the tax plus interest. If you wait until the tax authorities find it, for instance during [an audit](kb:boekenonderzoek-belastingcontrole), a penalty may be added.
As an entrepreneur, look beyond the return itself
An error in your income tax return rarely comes alone. If it was in your turnover or your costs, your VAT return is usually wrong too, and sometimes even the figures of the year before. So always check three things: your VAT over the whole year, your balance sheet at 31 December, and next year's return if you have already filed it. A wrong opening balance carries through.
If the error turns out to sit in a closed financial year, you do not always fix it retroactively. Sometimes the correction belongs in the current year instead. Which route applies when is explained in fixing an error in a previous financial year.
- Forgotten deductions are the most common reason to correct; run through the list of overlooked deductions before refiling.
- If you correct the profit, also check whether you still meet the hours criterion and whether the self-employed deduction is right.
- Keep both the old and the new version of your return, with a short note on why you corrected it. That saves explaining if questions come later.
Frequently asked questions
Can I simply file my return again?
Yes, as long as no final assessment has been issued. The last return filed is the one the tax authorities use. A provisional assessment does not stand in the way.
How far back can I correct?
With a request for an official reduction, up to five years after the end of the year the assessment relates to. If there is no assessment yet you adjust the return itself, and within six weeks of a final assessment you file an objection.
Will I get a penalty if I report an error myself?
For an ordinary mistake that you correct yourself, it usually stays at paying the tax plus interest. A deliberate-error penalty is meant for intent or gross negligence, and voluntary correction counts in your favour there.
I claimed too little deduction, but the assessment is final. Can I still do anything?
Yes, with a request for an official reduction within five years. Support the request with the documents that prove the deduction, so the tax authorities do not have to ask for evidence.
Do I have to adjust my VAT return as well?
If the error was in your turnover or purchase costs, almost always. Small corrections up to € 1,000 on balance go into your next VAT return; larger amounts are reported with a supplementary return.
Sources
- I found a mistake in the return I filedBelastingdienst · belastingdienst.nl
- Changing your tax returnOndernemersplein · ondernemersplein.overheid.nl
- Correcting a VAT returnBelastingdienst · belastingdienst.nl
Sources checked on
This article provides general information based on the rules known for 2026 and does not replace personal tax advice. For your specific situation, we're happy to take a look with you.
