Your tax assessment looks wrong: how to challenge it

The short answer

You challenge an assessment with a written objection (réclamation) to the tax authority that issued it, within 30 days from notification of the assessment. Once that deadline has passed, the assessment becomes final and can only be corrected in exceptional cases.Source: art. 132 para. 1 DBG/LIFD; art. 48 para. 1 StHG/LHID · checked on 27 September 2026

Key point: the deadline runs from notification, not from the date printed on the notice. Make a note of the date you received it.

Return and assessment: two different documents

Your tax return is a proposal. The assessment is the tax authority's decision, sent as an assessment notice (bordereau). It may follow your return exactly, or depart from it: a deduction disallowed, income added, assets revalued.

If you did not file a return, the authority assesses you at its discretion (taxation d'office), on an estimate. That is the hardest situation to challenge.

The deadline, canton by canton

The deadline is set by federal law, for direct federal tax as well as for cantonal and communal taxes, so it is the same everywhere. What changes is the required form and the address.

GE : 30 days from receipt of the assessment notice (cantonal and federal tax)VD : 30 days from notification of the decision, by signed objection sent by postVS : 30 days from notification of the assessment, in writingFR : 30 days from notification of the assessment, in writing to the SCCNE : 30 days from notification, in writing and signed, to the Service des contributionsJU : 30 days from notification, in writing, to the Service des contributions; reasons are mandatory against an assessment made ex officioBE : 30 days from notification of the assessment; a late objection is inadmissiblecantonal sources

What the objection must contain

• What you dispute: the item in the assessment, and the amount assessed.
• Why: the rule that applies, or the fact the authority did not take into account.
• What you ask for: the amount or correction you consider correct.
• The documents that prove it, attached or precisely described.
• Your signature. An unsigned objection, or one sent through a channel the canton does not accept, can be declared inadmissible.

After a discretionary assessment, the bar is higher

Against an assessment made at the authority's discretion, the objection is admissible only if the assessment is manifestly incorrect; the objection must state its reasons and the evidence.Source: art. 132(3) DBG/LIFD · checked on 4 October 2026

In practice, the objection only succeeds if it supplies what was missing in the first place: the complete return and its supporting documents.

What happens next

The authority reviews the file and issues a decision on the objection. What the law allows it to do: the authority may review every element of the tax and, after hearing the taxpayer, change the assessment even to their disadvantage.Source: art. 135 DBG/LIFD · checked on 4 October 2026

Key point: an objection reopens the whole file, not just the disputed item. Prepare it like a tax return, not like a letter of complaint.

If the decision on the objection is not in your favour, you can still appeal: 30 days from notification, to an appeals commission independent of the tax authorities.Source: art. 140(1) DBG/LIFD · checked on 4 October 2026

What this guide does not cover

Revision of an assessment that is already final, correction of withholding tax, which follows its own procedure, and back-tax proceedings. Each has different deadlines and conditions.

Checked on 27 September 2026.

Tax return