Filing and paying are separate jobs
Basel-Stadt gives you separate dates for sending in your tax return and paying your taxes. It is easy to assume that an extension covers both. It does not.
A filing extension does not move the cantonal tax due date. You also need to distinguish cantonal income and wealth tax from direct federal tax. They have different payment arrangements.
This guide is for private individuals dealing with Basel-Stadt taxes. It does not set the rules for Basel-Landschaft or other cantons.
Key dates for the 2025 tax year
The tax year is the year being assessed. For income and assets relating to 2025, the ordinary dates below fell in 2026.
| What | Date |
|---|---|
| Submit the ordinary tax return | 31 March 2026, unless a different filing deadline applies. |
| Direct federal tax | Due 1 March 2026; standard payment date 31 March 2026. Check the payment period on your bill. |
| Cantonal income and wealth tax | Due 31 May 2026, independently of when you file or receive the assessment. |
Sources: Basel-Stadt’s private tax-return guidance and the official 2025 tax letter (German PDF).
The cantonal due date also matters for interest. It is not the same as the payment period on a final bill. Basel-Stadt’s payment guidance generally requires a final cantonal bill to be paid within 30 days of delivery. Federal provisional or final bills also carry a payment period; follow your bill’s instructions.
What a filing extension changes
For the 2025 return, the filing deadline can be extended to 30 September 2026 free of charge. You need to request the extension; it is not automatic. Keep the confirmation of the deadline granted to you.
If documents are missing, deal with the filing deadline and the tax payment separately. Do not wait for the completed return to look at an amount already due. A payment extension is a separate matter, and it does not necessarily remove interest.
If you have missed a date, contact the tax administration and check your current account position. Do not assume that submitting an extension request retrospectively resolves a missed deadline.
Check the current filing and extension instructions and Basel-Stadt’s payment guidance.
Do not wait for the wrong bill
Basel-Stadt normally does not send a provisional cantonal tax bill. This can be a surprise if you expect a letter telling you exactly what to pay before the due date.
A provisional direct federal tax bill, by contrast, is based on the last definitive assessment. Treat it as a provisional calculation rather than proof that this year’s final tax will be the same.
Use the correct tax year and payment reference. Keep federal and cantonal payments separate and check that a transfer has reached the intended account. If your circumstances changed significantly, ask the administration which figures and payment instructions to use.
The official 2025 tax guide explains payment arrangements (German PDF). You can also order advance-payment slips from the canton.
Use the electronic tax account
The Basel-Stadt tax portal lets you inspect your tax-account statements, request transfers or refunds and generate payment slips. It is useful for checking what has actually been booked, rather than relying only on your bank’s outgoing transfer list.
An AGOV/ePortal login and access to the electronic tax account are not quite the same step. The tax account needs a one-time activation; the activation code is sent by post. Allow time for that before you need the information urgently.
Start from the canton’s official tax portal and BalTax information page.
BalTax, AGOV and practical help
BalTax Online is used to prepare and submit the return with its supporting documents. Keep the submission confirmation and a copy of what you sent. Paper filing is also available; follow the canton’s instructions for your chosen method.
If the obstacle is registering with AGOV, using BalTax or uploading documents, the canton offers appointment-based Help Points. These provide technical assistance, not individual tax advice. Check the current booking page for availability.
Living in another canton but taxable in Basel-Stadt?
Some people have a Basel-Stadt tax obligation because of property or a business connection there, while living in another Swiss canton. This is often called wirtschaftliche Zugehörigkeit, or economic affiliation.
Where the simplified procedure applies, BalTax allows you to upload the tax return from your canton of residence with the required details and supporting documents. Choose the relevant tax year. The simplified route described for residents of another Swiss canton does not apply to residents abroad, who must complete the full return.
See the 2025 BalTax instructions, page 9 (German PDF).
Common questions
Is the extension to 30 September 2026 automatic?
No. Basel-Stadt allows a requested extension of the 2025 filing deadline to 30 September 2026 free of charge. Check the deadline granted in your confirmation. This extends filing, not the cantonal tax due date. If your deadline has passed, contact the tax administration.
Source: Basel-Stadt’s filing and extension instructions (German).
Should I wait for a provisional cantonal tax bill?
Basel-Stadt normally does not issue one. Check the estimated amount and payment instructions yourself. Direct federal tax has a separate provisional bill, and the cantonal due date applies independently of when the return or assessment is completed.
Source: Basel-Stadt’s tax payment guidance.
Help in English
Want a hand with your Swiss tax return?
We prepare standard Swiss personal tax returns in English for a fixed fee of CHF 199. This includes normal bank accounts, common deductions, routine questions and one straightforward owner-occupied home.
Multiple or rental properties, self-employment and complicated international matters are quoted separately. We agree the fee before work starts. No surprise charges or commissions.
Send us your canton and the tax year you need help with. Please wait to send tax documents until we have agreed how to exchange them.
Email us about your returnSwiss tax returns only. We do not prepare US tax returns.