Tax glossary
Filing extension
A filing extension (Fristerstreckung) extends the deadline for submitting your tax return beyond 31 March — you must request it before the deadline expires, and if you do so in time it is straightforward.
In the canton of Zurich, your tax return must be submitted by 31 March of the year following the tax period. If you cannot meet this date, you request a filing extension. The request must reach the responsible municipal tax office before the current deadline expires — requests made after the deadline are no longer considered.
The request goes to the municipal tax office (Gemeindesteueramt) of your place of residence — many municipalities, including Winterthur, offer an online form. A first request submitted in time is deemed approved even without a reply. Extensions run to 30 November at the latest; beyond that only for credible extraordinary reasons (as of 2026, ZStB No. 132.1).
Important: the extension applies only to submitting the tax return. Your obligation to pay is not affected — provisional tax invoices must still be paid on time, otherwise late-payment interest is charged.
How to go about it
It takes just a few steps — all that matters is the timing.
- Submit your request before 31 March to your municipal tax office — in Winterthur online via the city’s e-services.
- Have the reference or ID number of your tax return to hand — it is on the cover letter that came with the forms.
- Choose a new submission date; for the first extension, the request alone is usually enough, with no reason required.
- Keep the confirmation — it is your proof in case a reminder arrives anyway.
What happens without an extension
If you neither file nor extend, you will receive a reminder with a short grace period — free of charge, but if you let that pass too, you risk a fine. If you let that pass too, the tax office will make an assessment at its own discretion — a discretionary assessment.
This regularly comes out significantly higher than your actual tax liability, and it can only be challenged by a reasoned objection within 30 days, submitted together with the missing tax return. Requesting an extension is far easier.
Extensions for tax advisers
If a tax adviser prepares your tax return, you often benefit from collective deadlines: recognised representatives receive a joint, longer deadline for all their clients. Let us know about your mandate in good time so that we can include you in this deadline.
Example: a missing certificate in March
At the end of March, a taxpayer is still waiting for the certificate from his pension fund. Rather than submitting an incomplete tax return — which would lead to a request for documents and a query — he applies online on 28 March for an extension until the end of September.
Cost: nothing. Effort: a few minutes. The alternative without a request: a reminder, then a fine and a discretionary assessment and an objection that takes far more time than the request would have.
Frequently asked questions: Filing extension
How long can I extend the deadline?
The first extension is normally granted without further ado. Further extensions are possible but may require a reason and incur a fee. The municipal tax office determines the specific practice.
I've missed 31 March — what now?
Submit your return as quickly as possible. A late extension request will no longer be considered, but prompt submission often prevents a discretionary assessment in practice.
Do I still have to make provisional payments despite the extension?
Yes. The extension only postpones filing. If provisional tax invoices remain unpaid, late-payment interest is charged.
Questions about this term?
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