The Most Common Mistakes in Swiss Tax Returns

Filing a tax return in Switzerland is a yearly challenge for many. With cantonal differences, complex forms, and ever-changing regulations, mistakes can easily occur – even for diligent taxpayers. Some errors cost only time, while others can lead to significant financial losses. This article shows the most common mistakes in the 2025 tax return and explains how to avoid them.

Mistake 1: Not Claiming All Deductions

Forgotten Medical Costs

Many taxpayers fail to declare medical and dental expenses because they don’t realize that costs not covered by health insurance are deductible. Deductible expenses include doctor visits, hospital stays, medication, dental treatments, and aids such as glasses or hearing aids – but only if they exceed the threshold (5% of net income for federal tax).

Education and Retraining

Work-related education and training expenses are often overlooked. Tuition fees, professional literature, and exam fees can be deducted if there is a clear professional link.

Donations and Membership Contributions

Donations to recognized charities are deductible up to 20% of net income. Political party contributions are also deductible – up to CHF 10,300 under federal tax. Receipts must always be kept.

Family Deductions

Many parents fail to take full advantage of child and childcare deductions. Example: up to CHF 25,000 per child in Zurich, CHF 10,000 in Basel-Stadt, and CHF 8,000 in Bern.

Mistake 2: Incomplete Asset Declaration

Bank Accounts and Securities

All assets as of December 31 must be declared – including interest and dividends. Forgetting an account or portfolio risks fines. Since Swiss and foreign banks exchange data, discrepancies are quickly detected.

Cryptocurrencies

More and more taxpayers own Bitcoin or Ethereum. These must also be listed in the securities and assets inventory. Valuation is based on the annual price list of the Federal Tax Administration (FTA).

Real Estate

Property owners must declare the taxable value, imputed rental value, and mortgages. Errors often occur when maintenance costs are not documented properly or incorrect flat rates are applied.

Mistake 3: Missing the Tax Deadline

In most cantons, the deadline is March 31. Late submission leads to a reminder from the tax office, often with fees or fines. If no return is filed at all, a discretionary assessment applies – usually higher than the actual tax burden.

Mistake 4: Missing or Incorrect Documentation

• Medical costs without receipts: deductions are not accepted without proof.
• Education without confirmation: missing course or exam receipts lead to rejection.
• Donations without receipts: only documented donations are deductible. Small donations under CHF 100 are often forgotten, even though they add up.
• Home office and work expenses: many claim them incorrectly. Only necessary costs (e.g. for a dedicated workspace) are deductible, not general rent or utilities.

Mistake 5: Issues with Digital Tax Solutions

More and more cantons are introducing online filing (e.g. Zurich with ZHprivateTax). Errors occur when flat rates and actual costs are mixed or when fields are entered twice. A common pitfall: claiming both flat-rate and actual expenses, which the tax office corrects – leading to delays or questions.

Mistake 6: Ignoring Special Situations

Certain life events have special tax rules. Overlooking them can be costly:

• Moving to or from Switzerland: different tax offices are responsible depending on timing.
• Death during the tax year: heirs must file a separate tax return.
• Starting or ending self-employment: additional forms and deadlines apply.
• Founding or restructuring a company: corporate obligations differ and are often underestimated.

Tips for an Error-Free Tax Return

• Start early: gather documents as early as January.
• Use checklists: to avoid missing deductions or receipts.
• Request deadline extensions: if time is running out.
• Use digital tools carefully: double-check data before submitting.
• Seek advice: for complex cases, tax specialists can help.

Conclusion: Attention to Detail Pays Off

The most common mistakes in Swiss tax returns are avoidable. Taxpayers who know their deductions, declare all assets, meet deadlines, and keep receipts organized save money and avoid trouble with the tax office. With good preparation and a clear system, the tax return can be handled stress-free – and the tax office will be satisfied.