Do I need a C permit to apply for Swiss citizenship?

Holding a settlement (C) permit is a formal precondition for ordinary naturalisation — you cannot apply on a temporary L or B permit. The C permit demonstrates that you already have a secure, long-term right to live in Switzerland.

Because the C permit itself usually takes several years of residence to obtain, securing it is an important milestone on the way to citizenship. Once you hold it and meet the residence-period and integration conditions, you can submit your application to your commune or canton.