Tax return in the Canton of Zurich: the 31 March deadline and how to extend it
Updated: · General information, not tax advice
In short: the tax return is due by 31 March, and that deadline can be extended — you apply to your municipal tax office before it runs out, normally until 30 September at the latest. But there is one 31 March deadline that is never extended: the one for the subsequent ordinary assessment if you pay withholding tax. That is the one people mix up.
1. The 31 March deadline
In the Canton of Zurich the tax return is due by 31 March of the year following the tax period — so the 2025 return is due by 31 March 2026.
If you only receive the documents after the end of February, you have 30 days from the day you receive them. That covers people who have just moved to the canton, and anyone whose paperwork arrived late.
2. The extension: on time, and at your municipality
Two things decide whether the request goes through:
- On time. The request has to be made before the deadline runs out. After that it can no longer be taken into account — and at that point you are not "a bit late", you are in default.
- At the municipality, not the canton. The office in charge is the municipal tax office of the municipality where you live. Many municipalities have an online form for it; the procedure differs slightly from one to the next.
Requests filed on time are granted until 30 September of the following year at the latest. Requests that go beyond 30 November are refused — unless extraordinary reasons can be credibly shown.
For self-employed people resident in the canton, the municipal tax offices extend the deadline to 30 September automatically; no request is needed.
3. The exception that costs money: withholding tax
This is where people mix up two deadlines that happen to fall on the same day.
If you pay withholding tax (Quellensteuer), no tax return is sent to you: you have to request a subsequent ordinary assessment if you want your real deductions to count. That request also has 31 March as its cut-off date — but it is a forfeiture deadline, and it is not extended. Once it passes, the year stays closed at the rate that was applied, even if money would have come back to you.
In short: one 31 March deadline can be moved, the other cannot. Details: withholding tax and the subsequent ordinary assessment.
4. What an extension is not
- Not a deferral of payment. It covers filing the return, not invoices or provisional instalments.
- Not a free pass. If you file nothing at all, you are assessed at the authority's discretion — and then you have to prove the assessment was too high, instead of simply declaring your own figures.
- Not a substitute for missing receipts. More time only helps if the time is actually used to get the paperwork together.
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6. Frequently asked questions
By when must the tax return be filed in the Canton of Zurich?
By 31 March of the year following the tax period. If you only receive the documents after the end of February, you have 30 days from the day you receive them.
How do I apply for an extension?
At the municipal tax office of the municipality where you live, and before the deadline runs out. Many municipalities have an online form for it; once the deadline has passed, the request can no longer be taken into account.
How long is the extension granted for?
Requests filed on time are granted until 30 September of the following year at the latest. Requests that go beyond 30 November are refused, unless extraordinary reasons can be credibly shown.
Does the extension also apply to withholding tax?
No. The request for a subsequent ordinary assessment also has 31 March as its cut-off date, but that one is a forfeiture deadline: it is not extended. Once it passes, the year is closed at the withholding tax rate that was applied to you.
7. Notice
This page is general information about deadlines in the tax return procedure and does not constitute tax or legal advice. The dates given come from the directive of the Finance Directorate of the Canton of Zurich on the tax return procedure, as at the date of this update; the procedure for the extension request is set by the municipality where you live, and other cantons have their own rules. You file the return yourself.