A person you have given express or implied permission to use your credit card. The person doesn’t have to be named in the credit card contract. An authorized user can use the card but is not legally responsible for paying the balance. His or her credit history can get a boost from being added to the account of someone with a stellar credit history. This led to the practice of piggybacking, where credit repair companies charge a fee for linking people with bad credit to those with good credit in order to boost their scores and make them eligible for loans they might not otherwise have been able to get. In 2007, the Fair Isaac Corp., which creates FICO credit scores, said it would exclude authorized user accounts from consideration. But it reversed itself the next year and said its new FICO scoring system would include the accounts but add safeguards to spot and prevent piggybacking.