The question of how long to keep credit card statements depends on the content, but the time period generally ranges from 45 days to seven years.
Small, "Normal" Purchases
If there are only small, "normal" personal purchases, keeping the credit card statement for about 45 days should suffice. This includes purchases for items such as grocery store products, restaurant meals and online orders for personal items. These cover things that are unlikely to be returned or which are one-time expenses (ie; a meal in a restaurant). Hold on to the receipts from each purchase and match them up with the monthly bill, to make sure there are no mistakes. Pay special attention to restaurant entries in which the tip was manually added after the main transaction was rung up. Be vigilant about looking for accidental double-swipes. If everything checks out, submit payment and shred the statement.
If the card has been used for anything tax deductible, save the statement, along with other supporting documentation, for seven years. Mark the entry so that you can find it easily in case of an audit. It is generally a good idea to keep the charges separate. For example, items purchased for a charity should go on a separate receipt, rather than mixed in with personal purchases. The more clear and obvious the transaction, the less risk of the Internal Revenue Service getting overzealous in an audit.
Items That May Be Returned
Keep credit card statements for at least 90 days if they contain big-ticket items, things covered by a warranty, or items that may be returned. Most stores will demand the original store receipt, but in case this is lost, there is a record of the transaction. With luck, the receipt can be tracked and retrieved in the storage system. Most major credit card companies maintain fairly robust databases that allow cardholders to search and manage their credit card records for up to several years. This can simplify things at tax time.