1. Charging a Big Balance to a Store Card
You're tempted to buy thousands of dollars' worth of furniture or appliances and charge it all to a store credit card that doesn't require payments for six months or even a year—and sometimes longer. But debt that sits untouched could drag down your score, especially if the balance is near the card's limit, says John Ulzheimer, president of consumer education at SmartCredit.com.
That's because your credit-utilization ratio—the amount of
debt you have relative to your credit limits—is calculated for balances on individual cards as well as overall. In addition, store cards tend to charge steep rates, so if you don't pay the balance before the interest-free period is over, you will rack up big charges.