Credit card companies extend credit to cardholders, which is like a temporary loan. Just like other lenders, credit card companies want to ensure that their cardholders will be able to pay them back. In some cases, this means asking for proof of income before allowing you to sign up for a card.
Since 2009, when the United States Congress passed the Credit CARD Act, credit card companies are not only legally allowed to but also legally required to make reasonably sure that prospective cardholders will be able to pay down their debts. This means that they are able to ask cardholders for proof of income or assets. For example, they may ask for pay stubs or bank statements. However, if they are able to obtain a satisfactory credit score or credit report, they may not ask for proof of income.
Cardholders Under 21
If you are under 21, the Credit CARD Act of 2009 requires credit card companies to collect proof of income or assets directly from you before giving you a credit card. However, you may not need to show proof of income if you can get someone older than 21 to cosign for you.