Closing a credit card almost always hurts your credit score, at least in the short term. There are two main reasons, and both come down to math.

Reason 1: Credit utilization goes up. Credit utilization is the percentage of your available credit that you're using. It's calculated across all your revolving accounts. If you have three cards with a combined $20,000 limit and $4,000 in balances, your utilization is 20%. Close one card with a $6,000 limit, and your available credit drops to $14,000. Your utilization jumps to 28.5% even though you didn't borrow a single extra dollar. Since utilization accounts for roughly 30% of your FICO score, this can cause a noticeable drop.

Reason 2: Average age of accounts shrinks. The length of your credit history makes up about 15% of your score. Closing an old card reduces the average age of your accounts. A closed card does remain on your credit report for up to 10 years after closure, so the impact on your age of accounts isn't immediate with FICO models. But VantageScore models drop closed accounts from their calculations sooner.

When it might make sense anyway:

The card has a high annual fee and you're not getting enough value to justify it. You can't resist the temptation to spend on it (behavioral reasons trump credit score optimization). The card issuer is charging you maintenance fees or inactivity fees. You're going through a divorce and need to separate joint accounts.

Better alternatives to closing:

Downgrade to a no-fee version. Many issuers let you convert a premium card to a basic card, keeping the account open and the credit history intact. Just call and ask. Sock-drawer the card. Put it in a drawer and make one small purchase every 6 to 12 months to keep it active. Set up autopay so you don't forget. Some issuers close accounts after 12 to 24 months of inactivity, so the occasional small charge keeps it open.

If you do close a card: Pay off the balance first (you'll still owe it after closing). Then call the issuer and request closure. Follow up in writing. Check your credit report 30 to 60 days later to confirm it shows as "closed by consumer" rather than "closed by issuer," since the latter can look negative to lenders reviewing your report manually.

The score impact of closing a card is usually 10 to 30 points, though it can be more if it significantly affects your utilization ratio. For most people, the hit is temporary and recovers within 3 to 6 months as other account activity fills in.