Forgetting to register
Some cash-back cards offer higher earnings potential in certain categories, but it all depends on timing and your participation.
Four cash-back credit cards in Bankrate's survey offer 3 percent to 5 percent back on rotating categories in addition to their 1 percent cash back on all other purchases. For example, Discover's It Card is giving 5 percent back on home improvement purchases (up to $1,500) from April to the end of June. From July to September, the card's special 5 percent category is gas station purchases.
But it doesn't happen automatically. Cardholders must register their cards online to capitalize on the greater cash-back rewards.
"Not signing up for rotating rewards is simply leaving money on the table," says McCracken. "There is no cost to sign up, so do it!"
The same goes for any special promotions that cash-back credit cards may run during the holidays or for back-to-school time. Check every letter, email or text from your credit card company to find out how to register.