File a tax return in Solothurn simply and reliably

Private individuals:
The tax return must be submitted by March 31 of the following year.

Companies:
Businesses are generally required to file their tax return by June 30.

Extension: A deadline extension can easily be requested online or in writing – usually until November 30 (for both private individuals and companies).
Note: Depending on the canton, fees may be charged for requesting an extension.

If the tax return is submitted late without an extension, reminder fees or fines may apply.

You have two options for submission:

• Online with eTax SO: The official eTax SO portal allows you to fill out, electronically sign, and submit your tax return. Supporting documents can also be uploaded digitally.
• Paper form: Alternatively, the tax return can be submitted by post — either filled out manually or printed from the online tool.

Tip: Submitting online is not only faster but also reduces the risk of queries thanks to automatic validations.

These tax aspects should be noted:

• Central cantonal tax authority without municipal tax rates: Tax authority lies exclusively with the canton, which levies a uniform tax rate of 104% (as of 2025). This simplifies the tax structure and ensures transparent, consistent rules throughout the canton.
• Progressive income and wealth taxes with fair gradations: Solothurn taxes income progressively with graduated rates and levies a wealth tax with different rates depending on asset classes.
• Tax-free compensation for militia firefighters up to CHF 10,000 per year: Compensation for militia fire service — including training, operations, and on-call duties — is tax-free up to CHF 10,000 per year, promoting voluntary service and public safety.
• Attractive deductions for research and development expenses: Self-employed individuals can claim an additional deduction for R&D contracts with third parties of up to 10% of taxable business income, capped at CHF 1 million. This strengthens innovation and entrepreneurship.
• Use of Artificial Intelligence (AI) in tax assessment: Solothurn is one of the pioneers in Switzerland using AI to automatically review and process tax returns. Around 20% of returns are expected to be fully automated, increasing efficiency and speed in tax administration.

Our specialists also advise you on more complex tax matters in Solothurn – for example:

• Moving into or out of the canton or abroad
• Self-employment or secondary income
• Withholding tax with voluntary ordinary assessment (SOTA)
• Capital withdrawals from pension funds
• Property ownership, rental, or sale
• Foreign income or assets

We carefully review your individual situation and ensure a tax-optimized filing.