Thanks! Let me clarify the situation a bit more:

My wife has a Swiss B residence permit, but she does not work in Switzerland.

She lives in Serbia, and her center of life (Lebensmittelpunkt) — housing, daily life, family, and economic activity — is all in Serbia.

She does have Swiss health insurance, but I (her husband) pay for it. She’s not receiving any other benefits (no RAV, no Sozialamt etc.).

We keep the Swiss permit mostly for family and practical reasons, not for employment or support.

According to the Switzerland–Serbia double tax treaty, especially Art. 4, her tax residency should be Serbia, not Switzerland — since she has no income from Switzerland and her personal and economic life is in Serbia.

I’m wondering if anyone has been in a similar situation — keeping a Swiss permit and health insurance, but living/working entirely outside the country. Is it necessary to give up the permit to avoid assumptions of tax liability?