Tax return in the canton of St.Gallen

Who is required to file a tax return in the Canton of St. Gallen?

In principle, anyone who was a resident of the Canton of St. Gallen on December 31 of the tax year is liable for tax. This also applies to individuals with economic ties to the canton, such as those who live outside the canton but own property or operate a business here.

Married couples who are legally and effectively living together file a joint tax return, regardless of their matrimonial property regime. In the event of separation, divorce, or the death of a spouse during the tax year, each person must file their own individual return.

Deadlines and extensions

In the Canton of St. Gallen, the 2026 tax return must be filed by March 31, 2027 . The documents will be sent out during the month of January 2027.

Exceptions apply: May 31, 2027, for the self-employed and for taxpayers with economic ties to the canton.

Deadline extensions are possible up to a maximum of December 31, 2027, and must be requested centrally through the canton. You will need your date of birth and register ID.

Important in all cantons: The request must be submitted before the standard deadline expires. Extensions cannot be granted retroactively, and reminder deadlines are generally non-extendable. If you neither file nor request an extension, you will first receive a reminder with a fee, followed by an assessment based on official discretion—which is usually to your disadvantage—plus a fine.

Good to know in the Canton of St. Gallen

• St. Gallen is one of the cantons with the most generous extension policy—filing by the end of the year is possible, provided you apply in time.
• Deadline extensions must be requested centrally from the canton, not from your local municipality.
• Extensions are only granted if all due taxes have been paid, so be sure to settle any outstanding tax bills first.
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Withholding tax: When you still need to file a tax return

If you work in Switzerland with a B or L residence permit, your taxes are generally paid directly via payroll deduction. However, this does not always settle the matter. Federal law determines when an ordinary tax return is additionally required, so the system is the same in all cantons.

Mandatory, with no option to choose

• Gross income of CHF 120,000 or more per calendar year from employment. For married couples, incomes are not combined for this purpose – the threshold applies per person. In this case, the tax authority will proactively send you a tax return.
• Income not subject to withholding tax, or taxable assets – such as from self-employed side activities, securities, real estate, pensions, or alimony. The authorities will not act automatically here: you must request the tax return yourself by March 31, 2027.

The second point is the most common pitfall. The CHF 120,000 threshold is set by federal law and applies uniformly everywhere. However, the thresholds for side income and assets are determined by the cantons themselves – about half do not publish any at all and decide on a case-by-case basis. If you have side income or significant assets, it is better to clarify this proactively than to wait for someone to contact you.

Voluntary filing is often worth it

If you are below the thresholds, you can apply for a subsequent ordinary assessment. This treats you the same as individuals subject to ordinary assessment and allows you to claim deductions that are not included in the withholding tax rate, or are only included as a flat rate:

• Pension fund buy-ins
• Contributions to Pillar 3a
• actual professional expenses, including weekly commuting costs
• self-funded education and training costs – up to CHF 13,000 per year for direct federal tax
• third-party childcare costs
• medical and disability expenses as well as interest on debt
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Residence abroad: Quasi-residency

If you live abroad and work in Switzerland, you can also apply for a subsequent ordinary assessment – provided that at least 90% of your worldwide income is taxable in Switzerland, with your spouse's income included in this calculation. In this case, the application must be submitted anew each year.

The deadline is strict

The application must be submitted by March 31, 2027 . This is a preclusive deadline and cannot be extended. If you miss it, you will remain subject to withholding tax for that tax period. If you leave Switzerland, the deadline ends as soon as you deregister with the municipality.

Conversely, once an application has been submitted, it cannot be withdrawn. If you fail to file your tax return after receiving a reminder, you will be assessed at the authorities' discretion and risk a fine. Once you are subject to mandatory retrospective assessment, you will generally remain in the ordinary tax procedure until your withholding tax liability ends.

If you switch to a C permit or marry a person with Swiss citizenship or a C permit, your withholding tax liability ends anyway – you will be subject to ordinary assessment starting the following month.

The most important deductions

Cantons and the federal government often have different maximum limits for the same deduction. This is exactly where the most common mistakes occur – and where the most money is left on the table. These items are almost always worth checking:

• Professional expenses – commuting costs, meals away from home, other professional expenses, and home office portions. The limits for these rates vary between the cantons and the federal government.
• Pillar 3a – the maximum amount is set by the federal government and applies equally in all cantons. What matters is whether you are affiliated with a pension fund.
• Pension fund buy-ins – fully deductible and usually the single biggest lever. Note the three-year blocking period for capital withdrawals.
• Childcare costs – daycare, after-school care, and childminders. The prerequisite is that the care is required due to employment, education, or incapacity to work.
• Insurance premiums and savings interest – a flat-rate deduction that increases if neither you nor your employer have made contributions to the 2nd pillar or pillar 3a.
• Medical and accident expenses – deductible to the extent that they exceed a percentage-based deductible of your net income.
• Further education and retraining – for direct federal tax, up to a maximum of CHF 13,000 per year, provided there is a professional connection.
• Property maintenance – either actual costs or a flat rate. It is worth comparing the two every year, as you are free to choose.
• Donations to non-profit organizations – deductible up to a percentage of taxable income, provided the organization is tax-exempt.
• Interest on debt – particularly mortgage interest, within the statutory limits.
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Childcare costs are subject to different limits at the cantonal and federal levels – for direct federal tax, the maximum deduction is CHF 25,800 per child.

iqtax checks your situation against current cantonal and federal rates and points out deductions that may apply to your case.

Which documents you need

You don't need to submit every single receipt, but you must be able to provide proof for every deduction you claim. Rule of thumb: include receipts for larger amounts; for smaller items, a precise description in your tax return is sufficient. You should keep everything until your tax assessment is final.

Mandatory attachments

• Salary statement from all employers during the tax period – without exception.
• Pillar 3a certificate, if you are claiming a deduction.
• Confirmation of pension fund contributions, if you have made payments.
• Tax statement or bank portfolio summary for securities, including balance and income as of December 31.
• Receipts for medical and disability expenses, if you are declaring them – including statements from your health insurance provider.
• Maintenance receipts and annual mortgage statements for home ownership.
• Childcare invoices for third-party childcare costs.
• Donation receipts for larger amounts.
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Also useful

• Bank statements as of Dec 31st showing balances and interest income for all accounts
• Receipts for professional expenses and continuing education costs
• Annual summary of cryptocurrencies with holdings as of Dec 31st
• Renewal fund statement for condominium ownership
• Receipts for alimony, support payments, and inheritances
• Proof of enrollment for adult children in education
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You don't need to memorize this.
‍After onboarding, iqtax creates a personalized, smart checklist for you. It shows you at a glance which documents are required for your situation, which ones you have already uploaded, and what is still missing. If anything is missing, we will proactively notify you – ensuring your tax return is complete before it is submitted.

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