How do you show proof of income for a visa application?

How do you show proof of income for a visa application?

For a Visa credit card:
Normally issuers require your last annual salary statement, or salary slips for the last few months.

For a visa to visit Switzerland:
To my knowledge, you are not required to show proof of income for a reqular visa (e.g. tourist visa). But if you want to get a residence permit, you generally have to show that you are employed by a Swiss employer, normally by providing a copy of the Swiss employment contract.