Correcting an error in your tax return

It happens to everyone: after filing your return you realise you forgot a deduction, entered a wrong amount or omitted some income. In Switzerland an error is not the end of the world, but the way to correct it depends on the moment you notice it and on the nature of the mistake. Acting through the right channel makes the difference between a simple adjustment and a problem.

Before the assessment arrives

If you notice the error after filing the return but before the authority has issued the assessment decision, the correction is generally straightforward. You can report the error to the competent office and submit the corrected data or the missing documentation.

At this stage the authority is still reviewing your file: a timely notice is usually accepted without friction. The practical rule is to act at once, as soon as you spot the error, attaching the supporting documents that justify the correction.

After the decision: the objection

When the assessment decision has already been notified, the ordinary tool is the objection. It is a challenge filed with the tax authority within a mandatory deadline from notification of the decision — typically short, of the order of a few weeks. In the objection you set out the error, indicate the correction requested and attach the evidence.

The critical point is the deadline: if you let the objection period lapse, the decision becomes in principle final and the ordinary avenues close. For this reason, as soon as you receive an assessment it must be checked immediately: verifying income, deductions and amounts while the deadline is still open is the most effective defence.

When the decision is already final

Once the objection deadline has passed, correction becomes more difficult, but not always impossible. Extraordinary remedies exist, with strict conditions:

• Revision: possible when new facts or evidence emerge that already existed but were not known and could not be raised earlier. It does not serve to remedy an oversight due to negligence, but to correct decisions based on elements that could not have been known.
• Correction of calculation or clerical errors: manifest material errors (a wrong tally, a typo in the amounts) can be rectified even beyond the ordinary deadline.

These remedies do not reopen the matter at will: they require precise conditions. Anyone who wants to “have second thoughts” about a choice made in the return, without new facts, will hardly qualify.

The error in your own favour: voluntary disclosure

There is a delicate case: when the error led you to declare less than was due, with income or assets not indicated. Here it is not about recovering a deduction, but about settling an unpaid tax.

The tool is the voluntary disclosure: if you report the omitted elements on your own initiative, before the authority discovers them, the Swiss system provides more favourable treatment in terms of penalties. The back taxes and the related interest remain due, but voluntariness is rewarded compared with an assessment made directly by the authority. It is an avenue to be assessed carefully and with qualified assistance.

Typical mistakes to avoid

• Not reading the assessment as soon as it arrives, letting the objection deadline lapse.
• Confusing the objection with the revision: the latter requires new facts, not a change of mind.
• Ignoring an omission in your own favour hoping it goes unnoticed: a timely voluntary disclosure is almost always the better choice.
• Correcting without supporting documents: every adjustment must be backed by documents.

In summary

• Before the assessment, the error is corrected with a simple notice.
• After the decision, the tool is the objection, within a short and mandatory deadline.
• Once the decision is final, only extraordinary remedies remain, with strict conditions.
• For undeclared elements there is the voluntary disclosure, which mitigates the penalties.

How we help you

We check your assessment decisions as soon as they arrive, prepare objections and corrections within the deadlines and guide you in delicate situations. Rely on our Tax Desk.