Cross-border & US-person tax in Switzerland

That means an annual US federal return on top of your Swiss return, plus foreign-account reporting: FBAR (the FinCEN 114 form, for aggregate foreign account balances over USD 10,000 at any point in the year) and FATCA (Form 8938, with higher thresholds that vary by filing status).

The US-Swiss tax treaty, the foreign tax credit and the foreign earned income exclusion typically prevent actual double taxation - Swiss tax is usually credited against US tax, or the first tranche of earned income is excluded. But you must still file both sides, and coordination between them is where mistakes hide.

The real trap is investing. PFIC (Passive Foreign Investment Company) rules impose punitive tax and heavy reporting on most non-US pooled funds, including UCITS ETFs, Swiss and European mutual funds, and some fund-based 3a products. US persons usually need US-domiciled funds and a PFIC-aware setup from day one - see investing & ETFs for how to structure this cleanly.

You'll file a final or partial-year return covering the period up to your departure. If you were taxed at source, that's usually the end of it; if you were in ordinary assessment, expect a cleanup return and a final assessment months later.

Your pillar 2 and pillar 3a then require decisions. If you're moving within the EU/EFTA, the mandatory part of pillar 2 must be kept in Switzerland in a vested-benefits account; if you're moving elsewhere, you may be able to withdraw everything. Withholding tax on lump-sum payouts depends on the foundation's canton, so foundation choice and staggering accounts across cantons can genuinely reduce the tax you pay - see vested benefits.

Practical steps: deregister at your commune to trigger the final tax steps and stop obligations like health insurance; plan the timing around Swiss and destination-country tax years and residency rules; and don't withdraw a lump sum in the same year as heavy Swiss income unless the maths supports it.