The basic rules
If you are a resident of a foreign country (France, Italy, Germany, Austria, Liechtenstein) and you commute to a Swiss employer, you're a frontalier. Your Swiss employer withholds source tax (Quellensteuer / impôt à la source) from your pay each month, at a canton-specific scheduled rate.
The country where you live then either (a) credits the Swiss source tax against its own ordinary income tax assessment, or (b) exempts your Swiss income entirely. The detail depends on the bilateral double-taxation treaty between Switzerland and your country of residence.
French residents — by canton
France has bilateral arrangements with most of the border cantons, but they differ wildly:
- Geneva (GE): source tax at canton scale stays in Switzerland. France then taxes your worldwide income and credits the Swiss tax. Net effect: you pay the higher of the two effective rates. Often more than a pure-French taxpayer of the same income.
- BE, BS, BL, JU, NE, SO, VD, VS: source tax goes to France (yes — the Swiss treasury collects it but transfers 4.5% of gross to your French departments via the 1983 accord). France taxes you on Swiss income normally. Net effect: roughly tax as if you were a Swiss resident at the canton's standard source rate.
- All other cantons (you'd commute very far): same as the GE model — source tax stays in Switzerland, France credits.
Italian residents — Ticino frontaliers
The 2023 Italy-Switzerland frontalier accord changed the math substantially:
- "Old" frontaliers (resident in 20km border zone before 17 July 2023): source tax stays in Switzerland; Italy doesn't tax the Swiss income. Net: low Swiss-only rate (~5% canton-only + federal).
- "New" frontaliers (post-17 July 2023 status): Italy taxes the Swiss income at its progressive scale, with Swiss source tax credited. Effectively Italian rates — much higher.
German residents
Germany taxes its residents on worldwide income, including Swiss employment. Switzerland levies a 4.5% withholding (per Art. 15a of the DE-CH double-tax treaty), which Germany credits against its own assessment. Net effect: roughly German tax rates.
Quasi-resident election (the trick)
Frontaliers earning above CHF 120 000 gross from a Swiss employer can elect quasi-resident status (Quasi-Ansässigkeit / quasi-résident). This means you file a full Swiss tax return — same as a real Swiss resident — and claim Pillar 3a, LPP buy-in, child allowances, alimony, etc. as deductions.
For high earners with significant deductible items, this often beats the flat source-tax rate. Many GE-based French frontaliers elect quasi-residence to claim 3a / LPP / mortgage interest.
How: tick the "Antrag auf Quasi-Ansässigkeit" / "Demande de quasi-résidence" box at filing time in March, attach proof of residence and family situation.
Pension contributions for frontaliers
Frontaliers contribute to the Swiss AHV (Pillar 1) and LPP/BVG (Pillar 2) like any Swiss-resident employee. Pillar 3a is available only if you elect quasi-resident status — without quasi-residence the 3a deduction doesn't apply to your Swiss source tax.
LPP buy-in: also requires quasi-resident status to deduct from Swiss tax. Without it the buy-in is just a Swiss-pension top-up with no annual-rate tax benefit (only the lump-sum benefit at retirement).
What Optiqo's calculator does and doesn't model
Today, Optiqo's calculator assumes Swiss residence. If you're a frontalier, the totals our calculator produces are upper bounds — the Swiss tax piece. Your actual liability depends on your country of residence's treaty position.
For the most common case (French frontalier in GE on quasi-resident election), our calculator approximates well — same scale, same deductions. For Italian "new frontaliers" in TI it under-estimates substantially because Italian progressive rates kick in on top.
A dedicated frontalier-mode calculator is on the roadmap. In the meantime, talk to a cross-border fiduciary if your situation is non-trivial. The bilateral-treaty math is fiddly.