Does applying for a supplementary credit card on someone's account affect either person's credit rating?
Savvy says: There are a couple of reasons why you want to grant another person access to your card, but the effect is the same no matter the reasoning behind it. Perhaps you want to add your partner to your account for the sake of convenience, or maybe you are trying to arrange a piggybacking situation. Piggybacking most often occurs when someone with excellent credit adds someone with poor or no credit as an authorized user on a credit card.
To see how adding another person to a credit card affects the credit of both individuals,
If you're the one being added to the card, be sure you're aware of the credit history associated with the particular credit card. Generally, the history of that card will be added to your personal credit report, which can be a good or bad thing depending on how the account holder has handled the card. It may not be in your best interest to be added to your spouse's card if he hasn't been great at paying on time.
While an authorized signer takes on the history of the established credit card, there's no affect on the account holder by simply adding another signer. However, the account holder is ultimately responsible for any charges made by the authorized party, and her credit can be greatly affected if this person acts irresponsibly.