A convenience check, also called a credit card check, is linked to a consumer's credit card account and can be used to make purchases or take cash advances with the credit card. CREDIT CARD SEARCH: Find the best 0% APR credit cards. To make a purchase, simply write a check for the purchase amount to a merchant and sign the check. Your credit card company pays the merchant when the check is cashed, and the amount of the check is deducted from your card's credit line. Write a check to yourself and cash it -- you're now using a convenience check as a cash advance. Using a convenience check, or two or three, for purchases or cash advances can wipe out your credit line pretty fast. Convenience checks are just that.