Should you close out old credit card accounts? When it comes to your oldest account, the answer is no. Closing old accounts could harm your credit score. That's because your credit history is based on the age of your accounts. Plus, about a third of your score is based on how much of your available credit you're using. So when should you close an old account? An industry expert told KOMO TV that a good reason is because a card issuer won’t waive an annual fee and you don’t want to pay that fee. Read Attorney General McKenna’s column, “How Creditors Determine Your Worthiness,” for more helpful information.