Blackbaud Merchant Services (BBMS) does not automatically reject a credit card because the card has expired.  The request is sent directly to the issuing bank. If the credit card is still in good standing, and has been part of a recurring gift cycle, the issuing bank may approve the transaction. If the credit card is no longer in use, then the transaction may be rejected.

Credit cards that have expired will process normally through BBMS, and by default, will be stored 6 months past the expiration date.

If you would like expired credit cards to be stored longer than 6 months past expiration:
Contact Support and reference this article.