Yes, if you are an on-the-job employee, you must provide the last three months (or six months) salary card (not a credit card) running bill. You can go to the bank and they will write it out and stamp it for you. Some still need to leave some money on the salary card (for example, there is still 30 thousand cash on the salary card, which should be reflected in the running bill. If there is not so much cash on the card, you can deposit it.

If you don't have a payroll card, I suggest you go to the Italian Consulate in official website to find out how to prove that you have enough income.

Credit cards cannot be used as proof.