*Loan,banking and credit>>>credit score

I have a good credit score (911). I want to add my son to my checking acct. He has not so good credit.?

How will this affect my credit rating?

As others have said 850 is the top FICO score. You might have somehow gotten a Vantage Score which goes from 501-990.

However, in answer to your question reguardless of your credit score checking accounts do not report to the credit reporting agencies so it will do nothing to help for his or your credit. The only time it will effect any credit is if either of you overdraft the account and don't pay it back. It will then be turned over to a collection agency and be placed as a negative item on any one who is on the account.

Credit scores top out at 820.
If I'm not mistaken, 850 is the highest possible FICO score, but I could be wrong. As for your son, adding him to your checking account should have no bearing on your credit, but he might spend more than his share, so that's what I would be more concerned about...
850 is the highest FICO score possible. The checking account has no effect on his or your credit score. If you want to add him to help him out add him to a Credit Card or Loan with a low balance in relationship to available credit.
work for a credit union
First of all 850 is the highest FICO score possible.

Second banks do not report checking or savings accounts since they are not loans so it will do nothing to help your Sons credit or hurt yours.
Finance Manager for over 7-years.