A deposit slip is a form supplied by a bank for a depositor to fill out, designed to document in categories the items included in the deposit transaction. The categories include type of item, and if it is a cheque, where it is from such as a local bank or a state if the bank is not local.

Bank deposit slips are used when you deposit money and checks in order to keep track of the money that you are putting into your account. Deposit slips are available from your financial institution. Banks use deposit slips to keep track of transactions. 

Depending on your bank, you may or may not have to fill out a deposit slip. Some ATMs deposit to your account based on the debit/ATM card you use, and they can even scan cash and checks in real time.