I live in Kanton Zürich. If I have an accident in another Kanton and have to go to hospital in that Kanton is the kost for my hospital treatment covered by my Basic Health Insurance ( Grundversicherung) or do I need supplementary insurance ( Zuzatzversicherung)Thanks

do you have a job?

Yes. I work in Switzerland. Visa " C ".

your employer pays your accident insurance.

if you work for a big company like UBS then you have P1 accident coverage.

smaller companies might not be as generous but the accident insurance will usually give you the choice, if you can make it, of being relocated for your treatment.

Then your employer should cover your accident insurance.

Is that to say that when I go on holidays in another Kanton ( in Switzerland) and have an accident or get sick then the costs are paid by my employer?

YES big letters