10. You Use the Wrong Credit Card
You have to be careful about which card you use when making big purchases. For example, if you buy a $1,000 television using a retailer’s card with a $1,000 limit, “you’ve just maxed out your card,” Ulzheimer said. If you put it on another card with a $30,000 limit and low utilization, it wouldn’t impact your score, he said.
But by using all of the available credit on one card — especially if it’s your only card — your credit score could drop 50 points or more, Ulzheimer said.
How to avoid it: Make sure, if you have a choice of cards, that you use one that won’t be maxed out. And don’t apply for a retailer’s card just to get a discount if the limit on that card will be close to the amount you’re charging.
How to fix it: Bring your account balance down below the 50% threshold as soon as possible.