How the subsequent ordinary assessment works in Thurgau
On a B permit, your employer deducts tax from your salary every month. That continues even if you also have to file a tax return. The tax office then assesses your total worldwide income and assets under the normal rules and credits the tax at source already deducted without interest. This procedure is called the subsequent ordinary assessment (nachträgliche ordentliche Veranlagung, NOV).
The framework comes from federal law and applies in every canton. A tax return is mandatory once your gross salary is at least CHF 120,000 in a tax year (Art. 9 of the federal ordinance on tax at source). For married couples, each salary is tested on its own. If you move to or leave Switzerland during the year, your regular salary is converted to twelve months, while one-off payments count in full; Thurgau refers to the federal ordinance for this (§ 22 para. 3 of the Thurgau tax ordinance). And once you are in the NOV, you stay there until your tax at source ends. For a comparison of all cantons, see our overview of the tax return obligation when taxed at source.
This article shows what applies in Thurgau. Status: tax year 2026, checked in October 2026.
Who has to file a tax return in Thurgau
The Thurgau tax act names two triggers (§ 113 para. 1). The Thurgau tax practice manual StP 113 No. 3 (September 2026 edition, in German) explains them in more detail:
- Salary. Your gross salary "reaches or exceeds" CHF 120,000 in a calendar year (StP 113 No. 3 section 2). For married couples, the two salaries are not added together for this test (section 1).
- Income not taxed at source, or assets. The manual lists examples: self-employed income, retirement pensions such as AHV or pension fund pensions, salary earned abroad that is at least partly taxed in Switzerland or only counts for the tax rate, alimony and maintenance payments, orphan's and widow's pensions, and income from movable or immovable property. The list is expressly not exhaustive. Anyone who owns "taxable assets" is covered as well (section 1).
- Your spouse's income abroad. If your spouse earns income abroad that is at least partly taxable in Switzerland and has to be taxed under the ordinary rules, your salary taxed at source is assessed under the ordinary rules too (section 1).
If you are married and living together with a person who meets one of these triggers, you are assessed under the ordinary rules as well (§ 113 para. 2). The act speaks of "assets and income", while the administration's manual speaks of income "or" assets. So the administration treats one of the two as enough.
A detail on the salary threshold: an older provision of the Thurgau tax ordinance (§ 23 para. 1, last amended in 2005) still says the salary must "exceed" CHF 120,000. The act, the manual and the federal ordinance say "reaches or exceeds" or "at least". This only matters at exactly CHF 120,000; if your salary is exactly there, we look at your case with you.
The Thurgau thresholds 2026 and their sources
| Criterion | Rule in Thurgau | Source |
|---|---|---|
| Gross salary | CHF 120,000 reached or exceeded, per person | StP 113 No. 3 sections 1 and 2 (edition 2026-09); § 113 para. 1 tax act |
| Assets, single | No amount published: individual check | StP 113 No. 3 section 1 |
| Assets, married | No amount published: individual check | StP 113 No. 3 section 1 |
| Income not taxed at source | No amount published: individual check | StP 113 No. 3 section 1 |
| Property abroad | named explicitly as an example of a mandatory NOV | FAQ on tax at source (as of 11 December 2020), p. 4 |
Checked in October 2026: tax act RB 640.1 (version in force since 1 January 2025), tax ordinance RB 640.11 (version in force since 1 January 2025), Thurgau tax practice manual edition 2026-09 (StP 113 No. 1 to 3, StP 113a No. 1), application form 113 version 2026, FAQ on tax at source (11 December 2020) and the short guide for people taxed at source (February 2021).
None of these sources names a franc amount for assets or extra income. The short guide from February 2021 (in German) goes further: according to section 4, income or assets not taxed at source trigger an NOV regardless of the amount, and you have to report to the tax office yourself. The document is still available, but the tax administration's current information page no longer links to it. The 2026 manual does not say this explicitly, but it does not contradict it either. Whether it is still current practice is something we check case by case, with the tax administration directly if needed.
What this means for you: if you have assets, property abroad or income not taxed at source, there is no line below which you can be sure. Check your situation well before 31 March.
Application, form and deadline in Thurgau
Mandatory because of assets or extra income. You must ask the competent authority for the tax return form by 31 March of the following year (§ 113 para. 3), so by 31 March 2027 for tax year 2026. Form 113 (in German) has a separate box for this: you confirm that you live in Switzerland and have further income not taxed at source or assets.
Voluntary application. If no trigger applies, you can apply for the NOV with the same form 113 (§ 113a). It goes to the Thurgau tax administration, tax at source department, in Frauenfeld (quellensteuer.sv@tg.ch). You receive the tax return forms once your application has been received and approved.
- Deadline 31 March, no extension. The application must be filed by 31 March of the following year (§ 113a para. 3). Late applications are not considered (form 113), and the deadline cannot be extended (short guide 2021, section 6).
- Both sign. Married couples and registered partners both sign the application (StP 113a No. 1 section 2).
- Moving abroad. If you leave Switzerland, the deadline ends when you deregister with your municipality. If you do not deregister properly, the deadline counts as expired (form 113).
- No way back. The NOV applies to the current year and all later years until your tax at source ends, even if your salary, income or assets later disappear (StP 113 No. 3 section 2). Switching back to tax at source only is not possible (form 113).
- Moving to another canton. The canton responsible is the one you live in at the end of the tax year (StP 113 No. 1 section 1).
The deadline for filing the tax return itself is a different matter. See our overview of tax return deadlines 2026 by canton.
Voluntary ordinary assessment: is it worth it?
In the NOV, the tax office works with your actual deductions and your municipality's tax rate. That can pay off if you contribute to pillar 3a, buy into your pension fund, pay for childcare or live in a municipality with a low tax rate. For the pillar 3a numbers, read our article on pillar 3a for B permit holders; for the key deductions in the canton, see tax optimisation in Thurgau.
Keep the commitment in mind, though: you stay in the ordinary assessment until your tax at source ends, including years in which the result is higher than the tax at source. And before you apply, check whether you are already obliged to file, for example because of property abroad. Then it is not a choice but an obligation, one you may already have had in earlier years.
If your issue is a wrong deduction on your payslip, for example a wrong tariff code, that is a recalculation of tax at source, not an NOV. See tax at source Thurgau: wrong code.
An example from Thurgau
Marco is single, lives in Frauenfeld and earns CHF 88,000 gross. He owns a small flat in Portugal that he uses himself for holidays. He has no other income outside tax at source.
- Salary: CHF 88,000 is below CHF 120,000. This trigger does not apply.
- Flat abroad: Thurgau names no amount. But the tax administration's FAQ lists owning property abroad explicitly as an example of a mandatory NOV.
Result: there is a lot to suggest that Marco has to file a tax return. Because the FAQ dates from 2020, he should clarify his case before 31 March 2027 and request the form in time. We are happy to do that check with him.
Check your situation
The calculator on our B permit tax return page asks for your canton, marital status, salary and assets. If your salary is below CHF 120,000, it shows for Thurgau that your case needs an individual check, because the canton names no amount.
Every case is different
Whether you have to file depends on your salary, your assets, the type of your income and your marital status. This article describes the rules for tax year 2026 and one simplified example; it does not replace individual advice. The legal basis is § 113 and § 113a of the Thurgau tax act and the tax practice manual StP 113a No. 1 on the voluntary application (both in German). More information is in the FAQ on tax at source and on the page for employees of the Thurgau tax administration.
If you would rather not fill in the tax return yourself, we can do it for you. Find out more on our page on tax advisory in Thurgau.