Do you discover after the objection deadline that a tax assessment is too high? A request for ex officio reduction may provide a correction route. It does not automatically reopen ordinary objection proceedings. The tax type, year concerned and reason for the reduction determine the applicable rules. First gather the assessment and your calculation. Where old years, new case law or rejection are disputed, a tax lawyer can assess the right route.
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1. First check whether objection really is unavailable
Record the document’s date, notification and when you actually received the assessment. Also retain the envelope and messages from your digital mailbox. An ordinary objection may sometimes remain possible or a substantiated reason for late filing may exist. A reduction request therefore does not automatically replace objection. If in doubt, have the deadline and any excusability assessed immediately so that an available legal route is not unintentionally lost.
Then identify the document you want amended. A final assessment, provisional assessment and separate decision serve different purposes. For a provisional assessment, use the applicable amendment route; this guide concerns correction after the ordinary opportunity to object to the relevant assessment or decision has expired. Also record whether your complaint concerns tax alone or additionally, for example, a penalty, interest or determination of a loss.
2. Calculate the deadline for the correct tax type
For income tax and corporate income tax, the Tax Administration states five years after the tax year. Its published explanation counts inheritance tax from the date of death and gift tax from the gift date. For other decisions, it states five years after the year to which the decision relates. Therefore do not copy a deadline from an income-tax assessment to an inheritance, gift or special refund scheme without checking.
Create a separate entry for each assessment with tax type, period, receipt date and calculated deadline. In a fictional example, someone discovers in October 2026 an error in income tax for 2021: under the ordinary five-year rule, the request must be received by 31 December 2026. An assessment dated much later does not automatically change that ordinary year-based calculation. Have exceptional situations assessed and retain proof that your request was received on time.
3. Show why the amount is substantively excessive
Start with the specific correction: which item is incorrect, what amount should replace it and why? Put original and requested calculations side by side. Add the principal underlying documents, such as an annual statement, invoice, bank overview or earlier correspondence on the same item. A pile of records without explanation does not clarify which assessment component is incorrect. Number attachments and refer to them specifically.
Distinguish a forgotten fact from a subsequently changed legal assessment. A deduction already existing at the time requires different substantiation from reliance on a recent judgment. Also identify relevant unfavourable information and explain how the proposed change affects the total. If several years connect, provide separate calculations with a short linking explanation. This keeps the requested amount for each year visible and avoids double counting.
4. Investigate limitations involving new case law
A favourable judgment for someone else does not automatically entitle you to reduction of a final assessment. For income tax, Article 45aa of the Implementing Regulation limits reliance on new case law; for other national taxes, policy under Article 65 of the General State Taxes Act may matter. Therefore compare the date your assessment became final with the legal development relied on. Also check for a special scheme or exception.
In 2024, the Supreme Court clarified that the inspector cannot use that limitation where the assessment relied on a legal view the inspector could not reasonably regard as correct. This is assessed against the state of the law when the assessment became final. It is a targeted exception, not a general right to correction following every later judgment. Have an adviser explain why a judgment affects your situation; its publication date or a news report alone is insufficient.
5. Submit an identifiable request to the correct office
For income tax, resubmitting the return through Mijn Belastingdienst can serve as a request under the conditions stated by the Tax Administration. A letter is also possible. Include name, address, date, tax year, assessment number, reason and signature. Use the office address on the assessment. Keep the version actually submitted and attachments so that it is later clear which correction you requested and which facts you relied on.
For other taxes, the Tax Administration describes a letter procedure with addresses depending on tax type. Check the current address when sending, especially for inheritance tax, gift tax and BPM vehicle tax. Give a representative clear instructions specifying the assessments and years involved. Request an acknowledgement and schedule follow-up. A telephone conversation can help explain the handling, but also retain important commitments and further questions in writing in your own file.
6. Keep payment separate from the correction decision
A reduction request does not mean you may independently ignore an outstanding payment obligation. Separately check whether deferral was granted and its conditions. For payment problems, ask about the appropriate collection procedure. The inspector assesses the tax correction while the collector handles collection. Keep both correspondence streams together so that a substantive discussion does not unnoticed lead to arrears or a missed response to a collection letter.
If the five-year period has also expired, explain why you are late. The Tax Administration additionally describes limited review by the collector where an excessive assessment can demonstrably be shown. This is not a general extension of the deadline or the same as an ordinary refund after reduction. Have an adviser establish specifically what result remains attainable, especially where payment has already been made or third parties attach consequences to the assessment.
7. Assess legal protection after rejection
For income tax, a complete or partial rejection under Article 9.6 of the Income Tax Act 2001 takes the form of a decision open to objection. Immediately check the remedies reference and deadline. This additional legal protection does not automatically apply to every tax type. A decision under Article 65 of the General State Taxes Act is in principle not open to objection; therefore do not assume the same route exists for corporate income tax or BPM.
For legal consultation, bring the original assessment, complete request and rejection. Identify exactly which component was assessed incorrectly: the deadline, evidence, applicable scheme or interpretation of new case law. Ask which procedure actually provides access to review and what it can achieve. A service complaint does not replace a remedy against an appealable decision. Therefore monitor the decision period and your own next step separately.
Frequently asked questions
Do I always get five years from the assessment date?
No. The starting point differs by tax type. For income tax and corporate income tax, the Tax Administration refers to the tax year; for inheritance tax, the death date; and for gift tax, the gift date.
Can I object to every rejection?
No. Income tax has special legal protection through Article 9.6 of the Income Tax Act 2001. Do not extend that possibility to a decision about another tax without investigation.
Is a later favourable judgment enough for reduction?
Not automatically. New case law may actually be an obstacle for a final assessment. The relevant scheme, timeline and any exception must be assessed.
Sources
These sources relate to this page. For a specific case, check current rules and your own documents.
- Belastingdienst — Te laat voor bezwaar Accessed: 2026-10-23
- Belastingdienst — Vermindering inkomstenbelasting Accessed: 2026-10-23
- Belastingdienst — Vermindering andere belastingen Accessed: 2026-10-23
- Hoge Raad — ECLI:NL:HR:2024:667; officiële XML gelezen Accessed: 2026-10-23
- Kennisgroepen Belastingdienst — KG:206:2023:8 Accessed: 2026-10-23
- Officiële bekendmakingen — Fiscale verzamelwet 2023 toelichting Accessed: 2026-10-23
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Editorial team Tax law in the Netherlands
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