j8ear

If you add someone to one of your long standing perfectly paid credit cards as an authorized user...

IT WILL SHOW up on that persons credit report and CAN improve their credit score. You don't even have to give that person a card.

If that's your question then YES.

If co-signing for someone else's loan will boost that other person's credit score? This will eventually happen but initially (for all parties concerned) your credit score will lower as you have 'new' debt obligations, and balance to maximum is always high at loan inception. Off the bat this will produce a score reduction.

-bear

edit: Remember that adding someone to your roach, maxed out, lots of lates credit card will drop the person's credit score as well. The only thing this is effective for is adding, say, a perfect ten year history, on a low balance, high limit credit card, perhaps from parents or an older sibling. It's really the extra ten years of credit history that will significantly boost credit scores.

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It's alot easier to ask for forgiveness then it is to ask for permission.