B permit taxed at source: should you apply for subsequent ordinary assessment? When it gets you a refund, when it costs you, and why there is no going back

You live in Switzerland with a B permit, your employer withholds tax at source from your salary every month, and you have heard that a refund is possible. That is true, but it comes at the price of a decision you cannot reverse: subsequent ordinary assessment (SOA; TOU in French). Once requested, it replaces the deduction every year with a full tax return, until you are no longer taxed at source. Based on the federal texts and on the practice published by Geneva, Vaud and Zurich, this guide describes when the application pays off, when it turns against you, and how to decide before 31 March.

It concerns people resident in Switzerland. If you live in France, Italy or another country and work in Switzerland, the SOA is subject to other conditions, described in our guide to quasi-resident status.

1. Who is taxed at source, and until when?

Every foreign employee resident in Switzerland without a C permit is taxed at source, unless married to a Swiss citizen or a C permit holder. This regime ends with the C permit, naturalisation, such a marriage or departure from Switzerland (if you continue to work there from abroad, you remain taxed at source, but as a non-resident).

Under article 83 of the Federal Act on Direct Federal Taxation (DBG), employees without a settlement permit who are resident or staying in Switzerland for tax purposes are subject to withholding tax on their income from employment. This covers holders of a B or L permit, but also, for example, provisionally admitted persons. Spouses living in the same household are not subject to withholding tax if one of them is Swiss or holds a C permit (para. 2). Our guide to residence and work permits sets out the conditions for moving from the B permit to the C permit.

The deduction is calculated by your employer according to a cantonal tariff, which combines federal, cantonal and municipal tax in a single rate (art. 33 of the Federal Act on the Harmonisation of Direct Taxes, StHG). Professional expenses, insurance premiums and family charges are built into it as flat-rate amounts. Our guide to withholding tax tariffs explains how to read your code (A0, B1, C2…).

The regime ends when you obtain a settlement permit or marry a Swiss citizen or a C permit holder: you are then taxed under the ordinary procedure for the whole year, and the tax withheld until then is credited without interest (art. 12 of the FDF Withholding Tax Ordinance, QStV). This rule matters for the decision: the SOA you apply for today binds you until that date, which may be one year away or ten.

2. Are you already subject to mandatory SOA?

Before asking yourself whether to apply for it, check that it does not already apply: a gross salary of at least 120,000 francs, income not taxed at source or wealth above the cantonal threshold makes it mandatory.

The DBG distinguishes two regimes. Mandatory SOA (art. 89) applies without any application on your part. SOA on request (art. 89a) is open to those who meet none of the conditions of the first. The conditions, set by the DBG and the StHG, are:

• Gross income from gainful activity of at least 120,000 francs in a tax year, yours or your spouse's if you are married (art. 9 QStV). The threshold is compared in francs: our guide to salaries in dollars shows how the exchange rate can push you over it.
• Income that is not subject to withholding tax (art. 89, para. 1, let. b, DBG): investment income, rents, self-employment, maintenance payments received, foreign income. The cantons set the thresholds.
• Taxable wealth (art. 33a, para. 1, let. b, StHG), according to the cantonal thresholds.

The cantonal thresholds published for 2026:

Sources: Geneva page Quand demander ou annoncer une TOU ? (when to apply for or report an SOA) and 2026 directives on withholding tax (No. 8.2.1); Vaud form 21049 (version of 28 January 2026); Zurich page Nachträgliche ordentliche Veranlagung. The Geneva page adds to this list four situations that the 2026 directives do not repeat: owning real estate, self-employment in Geneva, another activity abroad, a spouse with no gainful activity. If you are in one of these cases, in particular if your spouse has no gainful activity, ask the withholding tax department whether an SOA already applies to you before applying for one.

3. What the SOA changes in practice

The monthly deduction becomes an advance payment. Your final tax is calculated on a full tax return, as for a C permit holder, and the difference is refunded to you or invoiced.

Without an SOA, the law is unambiguous: under article 89a, paragraph 4, DBG, withholding tax replaces the direct federal tax on income from employment levied under the ordinary procedure, and no further deduction is granted afterwards (the same rule applies to cantonal and municipal taxes, art. 33b, para. 4, StHG). With an SOA:

• You fill in a tax return, sent by the administration. In Geneva, you have two months from receipt to return it with the supporting documents (2026 directives, No. 8.2.4).
• Tax is calculated under the ordinary rules: all your deductions, your income and your wealth, at the rate of your municipality of residence on 31 December (FTA Circular No. 45, No. 11.1; art. 107, para. 4, DBG).
• The tax withheld by the employer is credited without interest (art. 89, para. 6, DBG). If the ordinary tax is lower, the difference is refunded to you; if it is higher, you pay the balance.
• The 35% Swiss withholding tax on investment income deducted from your Swiss interest and dividends can be recovered in the SOA. In Geneva, the 2026 directives specify that, for a resident taxed at source, it can only be obtained in the context of the SOA. Our guide to refunding the 35% Swiss withholding tax describes the other routes.

Do not confuse the SOA with a correction. In Geneva, a request for correction (DRIS) fixes a wrongly applied tariff (wrong code, a child left out) without moving to a full tax return; the two procedures are alternatives, and you cannot file both for the same year (2026 directives, No. 8.2). Our guide to withholding tax correction in Geneva describes it.

4. When the SOA makes you better off

When you have deductions that the tariff does not include. The saving is roughly equal to their amount multiplied by your marginal tax rate.

The deductions that only the SOA allows

The tariff includes, on a flat-rate basis, your ordinary OASI and LPP contributions, your professional expenses and your insurance premiums. According to FTA Circular No. 45 (No. 10.1), the SOA serves to claim deductions that the withholding tax tariff does not take into account, or only on a flat-rate basis. The official lists of Geneva and Zurich cite:

• 2nd pillar buy-ins (pension fund), often the biggest lever. Our guide to the LPP buy-in calculates whether it pays off.
• Pillar 3a contributions: up to 7,258 francs in 2026 for an employee affiliated with a pension fund, according to the Federal Social Insurance Office; this ceiling rises to 7,373 francs in 2027. Our guide to the three-pillar system places pillar 3a in context.
• Childcare costs paid to third parties.
• Maintenance payments made, which Geneva cites for minor children.
• Training and further education costs that you pay yourself (in Zurich, up to 12,000 francs a year).
• Actual professional expenses above the flat-rate amount (long commutes, weekly stays away from home), debt interest (cited by Zurich) and unreimbursed medical expenses.

An order of magnitude

Take a single engineer with a B permit who lives in Lausanne, with a gross salary of 95,000 francs, savings of less than 60,000 francs and no income other than her salary: she is not subject to mandatory SOA. In 2026, she makes a 12,000-franc buy-in into her pension fund and pays 7,258 francs into a pillar 3a account, giving 19,258 francs of deductions that are not in the tariff. What these deductions save her depends on her marginal rate, that is, the tax levied on her last francs of income. The table illustrates this with three hypothetical rates:

These figures are not a calculation of her tax: they show that, with a buy-in, the stakes run into thousands of francs. Her actual marginal rate can be estimated with the FTA tax calculator, by comparing the tax calculated with and without the deductions (section 7). A buy-in is also capped during the five years following arrival in Switzerland, as our guide to the LPP buy-in explains. And the actual saving departs from this product for the reasons described in the next section: her municipality's tax multiplier, actual expenses lower or higher than the flat-rate amounts.

The municipality: a gain or a loss depending on where you live

The tariff does not know your municipality: it applies an average. In Geneva, the law provides that the municipal surcharges (centimes additionnels) are calculated on a flat-rate basis (art. 3 of the Geneva withholding tax act); the Vaud Council of State states that the 2026 tariffs take account of the average cantonal and municipal tax multiplier; Zurich applies a weighted average of municipal tax multipliers of 109.90% without church tax and 116.00% with it (2026 tariff parameters). The SOA, by contrast, applies the actual municipal tax multiplier (2026 Vaud instructions, No. 2.3.2). On this item alone, the SOA makes you better off if your municipality taxes less than the average, and costs you if it taxes more; the other effects described in the next section can offset or worsen this gap.

5. When it becomes an irreversible trap

The application cannot be withdrawn and applies to all following years. A winning buy-in year can open a series of years in which you pay more than with the deduction at source.

What the texts say

• Once filed, an application cannot be withdrawn (art. 10, para. 1, QStV).
• SOA on request applies, like mandatory SOA, until the end of liability to withholding tax (art. 89a, para. 5, and 89, para. 5, DBG). FTA Circular No. 45 specifies that the administration then carries it out automatically, every year (No. 11.3).
• If you are married, the application extends to your spouse (art. 89a, para. 2, DBG). In the event of divorce or separation, each of you remains subject to the SOA until the end of your own taxation at source (art. 10, para. 2, QStV).
• The Geneva directives add that it is no longer possible to withdraw the application, even if the assessment ultimately turns out to be unfavourable (No. 8.2.3).

This is a major difference from people who live outside Switzerland: a quasi-resident's SOA is requested year by year, a resident's only once, for all the years to come.

The situations in which it turns against you

The canton of Vaud sums it up in its 2026 instructions: the tax result determined under the SOA can lead to a higher or lower tax burden than the withholding tax deducted by the employer. On top of that comes the administrative burden: a tax return every year, supporting documents, and in some cases advance payments or a balance to pay.

6. The 31 March deadline and leaving Switzerland

The application must be filed by 31 March of the year following the tax year at the latest. The deadline is not extended; if you leave Switzerland, it expires as soon as you register your departure.

• For the 2026 tax year, the deadline is 31 March 2027 (art. 89a, para. 3, DBG). You can therefore pay into your 3a or make your buy-in until 31 December 2026, then decide in early 2027, with your salary certificate in hand.
• No extension: Zurich writes that "die Frist kann nicht verlängert werden" (the deadline cannot be extended) and describes it as a forfeiture deadline; Geneva speaks of a strict deadline. A late application is not examined, and the deduction at source becomes final.
• An incomplete application is not lost outright: the administration sets you a deadline to correct it, failing which the tax withheld becomes final (FTA Circular No. 45, No. 11.3; in Zurich, ten days).
• If you leave Switzerland, the application must be made at the latest when you register your departure (art. 89a, para. 3, DBG). According to FTA Circular No. 45, if you do not register your departure properly, the deadline is deemed to have expired. In Geneva, you must go to the withholding tax department within the fifteen days before departure. Our departure checklist places this step in the timeline.

7. Run the numbers before applying, in five steps

Compare the tax withheld over the year with the ordinary tax your tax return would produce, for the year concerned and for a "normal" year with no exceptional deduction.

1. Note the tax withheld on your salary certificate or your payslips for the year.
2. List your deductions: buy-in, 3a, childcare costs, maintenance payments, training, actual professional expenses, actual insurance premiums, debt interest.
3. Estimate your taxable income: net salary (after OASI, unemployment insurance and ordinary LPP) minus these deductions. Add your wealth and your other income.
4. Calculate the ordinary tax in the FTA tax calculator, choosing your exact municipality. Compare it with the tax withheld.
5. Redo the calculation for a year without a buy-in, with only your recurring deductions (3a, childcare costs). If this "normal" year costs you more than the deduction at source, the gain from the buy-in year must cover the losing years until the end of your taxation at source.

If the gap is small or the situation is complex (a couple, wealth close to the threshold, real estate abroad), have the calculation confirmed by a fiduciary or by your canton's withholding tax department before filing the application: it cannot be corrected.

8. How to file the application in Geneva, Vaud and Zurich

A written application, signed by both spouses if you are married, specifying the tax year concerned. Each canton has its own channel.

In the other cantons, the application is sent to the withholding tax department of your canton of residence on 31 December, under the same federal rules (FTA Circular No. 45, No. 11.3).

9. Key takeaways

Without an application, the withholding tax of a B permit resident is final: no buy-in, no 3a contribution and no childcare costs are deducted. Subsequent ordinary assessment opens up these deductions, but it also replaces the tariff's municipal average with your municipality's tax multiplier and the flat-rate amounts with your actual expenses, and it covers your wealth. Above all, it cannot be withdrawn: it applies, to you and your spouse, until the C permit, naturalisation, marriage to a Swiss citizen or a C permit holder, or departure.

Three reflexes: first check that you are not already subject to mandatory SOA (120,000 francs, wealth, other income); run the numbers for two years, the buy-in year and an ordinary year; file by 31 March at the latest, or when you register your departure if you leave Switzerland.

10. Frequently asked questions