Dear Liz: My 33-year-old son has horrible credit scores. If I added his name to my credit card, would it have a positive effect on his score without any negative ramifications to mine? Could any of his creditors come after me?

Answer: Adding someone to your credit card as an authorized user can have a positive effect on their credit scores without negatively affecting your own or obligating you to pay their other debts. You would be responsible for any debt your authorized user incurred on the card.

In your son’s case, though, being added as an authorized user probably won’t help much.

When someone has fallen behind on their bills, the effect on their scores depends on three main factors: recency (how recently did a late payment occur?), severity (how far behind are they — 30 days, 60 days, 90 days or more?) and frequency (how many accounts have late payments?).

One skipped payment can knock 100 points or more off good scores but won’t result in “horrible” credit. Truly bad credit typically requires someone to be well behind on a number of accounts in the recent past. The fact that you’re worried about his creditors indicates that he may not have resolved his financial problems enough to start rebuilding his credit.

What he should do now depends on his circumstances.

If he still has a job, he may be able to arrange a payment plan or settle debts with collectors. If his income has dropped or he’s otherwise unable to pay, he may need to consider bankruptcy.

Once his past debts are resolved — either paid, settled or legally erased — he can take steps to improve his credit, one of which could include being added to your card. A credit builder loan, offered by many credit unions, also could help, as could a secured credit card, which requires a deposit.

It’s crucial that he be able to make all his payments on time, however. If he falls behind again, he’ll offset any progress that’s been made.