How a wrong deduction ends up on your payslip
If you are taxed at source — which applies to most B-permit holders — your employer deducts the tax straight from your salary and pays it to the cantonal tax office. How much depends on a short code on your payslip, usually near the top and often just three characters long. Behind it sit three pieces of information: your civil status, whether your spouse also works, and how many children you can claim.
The code has three parts: the tariff letter, the number of children you can claim, and a letter for church tax. C3N therefore means: dual earner, three children, no church tax.
The code is set when you join, based on the personnel data available at the time, and has to be adjusted whenever something tariff-relevant changes — marriage, a birth, a change of denomination, or your spouse taking up work. In practice that only happens if the change is reported and then processed in payroll. If either step is missed, the system keeps calculating correctly for years. Just from the wrong starting point.
What often goes wrong for married couples
Two rules get mixed up regularly.
The first: if you both work, tariff C applies — not the tariff for households with a single income. That sounds obvious, but it is easily overlooked when one of you started working later.
The second: if you are married, both work and have children you can claim together, the number of children is generally counted for both of you under tariff C — not just for one parent.
Zurich shows this in its own tariff guidance with an example: a married couple, both taxed at source, one shared child. The husband gets C1Y, the wife C1N. The number appears for both — only the church tax marker differs.
And no, that is not claiming the child deduction twice. The number in the tariff belongs to the flat-rate calculation on each individual salary. If an ordinary assessment follows later, your income is taxed jointly and the child deductions follow the ordinary rules there.
Our use case: a married couple with three children they can claim, both working, salaries of CHF 174'000 and CHF 157'000. The husband's payslip shows B2, the wife's C0. Both should have been C3.
Two things were wrong on his payslip at once
B2 means: married single earner with two children. It should have been C3 — dual earner with three children. Neither the letter nor the number was right.
What makes this interesting is that the two errors pull against each other. At his salary, using the official Zurich 2026 tariffs without church tax:
- The wrong letter deducts too little — B3 against C3 is 2.09 percentage points.
- The missing third child deducts too much — B2 against B3 is 1.43 points the other way.
That leaves 0.66 points. His deduction therefore looked almost unremarkable, even though two entries were wrong. On the wife's payslip the letter was right and only the three children were missing — which comes through in full, at 5.64 percentage points.
What that means in Zurich
Calculated with the official Zurich 2026 tariffs without church tax, assuming twelve equal monthly salaries with no 13th salary and no bonus:
- Husband: 8.10 % instead of 8.76 % — around CHF 1'148 too little a year
- Wife: 13.03 % instead of 7.39 % — around CHF 8'855 too much a year
- Together: around CHF 7'706 too much
In this use case the missing child allowance on her side weighs far more than the opposing error on his. That is why a substantial overpayment remains. On a joint account you would see none of it — the two deviations run against each other and look unremarkable together.
What these CHF 7'706 are — and what they are not
This is the most important point in the article: a wrong tax-at-source deduction is not the same as a wrong final tax bill.
The tariff only determines how much is prepaid during the year. In this use case one spouse already earns more than CHF 120'000, so the couple is assessed under the ordinary rules anyway — and in that assessment the tax at source actually paid is credited against the final tax.
The wrong code therefore affects your liquidity first: month after month, more leaves your account than necessary. The money is not lost because of it.
How other cantons compare
Same situation, same salaries, only the canton of residence changes. Two figures determine how strongly a wrong code bites: how much the earner status weighs, and how much the children relieve. Both differ considerably between cantons.
| Canton | Single earner instead of dual earner | Three missing children |
|---|---|---|
| Geneva | 6.44 pt | 5.57 pt |
| Aargau | 4.40 pt | 3.40 pt |
| Thurgau | 3.94 pt | 2.89 pt |
| St. Gallen | 3.81 pt | 4.43 pt |
| Zug | 3.27 pt | 3.49 pt |
| Schwyz | 3.00 pt | 2.35 pt |
| Zurich | 2.09 pt | 5.64 pt |
2026 tariffs, without church tax, calculated on the same salaries as above.
Zurich is the outlier: the earner status weighs least of all seven here, the children most. In Geneva it is almost the reverse — the wrong letter bites more than three times as hard as in Zurich.
What that adds up to for a household depends heavily on the actual salaries. In Aargau, Thurgau and Schwyz the two effects sit so close together in our example that a few thousand francs of salary difference decide whether too much or too little was deducted.
Why the deduction can never quite fit with two salaries
Your employer does not know what your spouse earns — and is not supposed to. So tariff C works with a standardised spouse income for setting the rate: for 2026 that is a maximum of CHF 5'875 a month, or CHF 70'500 a year.
The further your spouse's actual income sits from that assumption, the further the tax-at-source deduction can drift from the later ordinary assessment. Whether that ends in a balance to pay or a refund also depends on your actual deductions, your municipality and your denomination.
This is exactly why a review before the bill arrives pays off. What actually adds up only becomes visible once both salaries are calculated together — and by design, the tax-at-source deduction cannot do that. A tax adviser works out in advance what you will effectively owe, how much to set aside each month, and which deductions you can claim that the tariff does not provide for. It is a manageable calculation — but somebody has to do it before the assessment lands in your letterbox. More on our tax advisory for Zurich.
Above CHF 120'000 a tax return comes on top
If you earn more than CHF 120'000 gross, you also file an ordinary tax return — every year. For married couples the threshold is measured per person, not added together, and it is enough for one of you to cross it.
The monthly deduction is then only a payment on account. The real bill comes later, and it almost never matches exactly. A high deduction does not automatically mean a high tax bill — and a low one does not mean you got off lightly.
How to check your payslip in five minutes
Take your latest payslip, find the field with the tax code and work through three questions: is the civil status right? Is it recorded that you both work? Is the number of children you can claim right, including after the most recent birth?
A correct code is a good first check, but not a complete one. With several employments or additional earned income, the rate-determining income may have to account for total income or a projection. You can have C3 correctly on your payslip and still pay the wrong rate.
If you find something, report it to HR. For the current year payroll can correct the tariff. For years already closed, deadlines apply — in Zurich a tax-at-source correction should generally be requested by 31 March of the following year.
The series: the same error in other cantons
- Geneva — the most expensive tariff letter
- St. Gallen — both effects strong
- Zug — low rates, large relative deviation
- Aargau — the error nobody notices
- Thurgau — when the household pays too little
- Schwyz — the flattest tariffs
- What one child is worth — seven cantons compared