If you cosign on a car note with good credit but then after a year or so the cosigner's credit is in the toilet does it affect the primary's note or interest rate?

it should not affect the primary account holder's interest rate on that account, or the secondary's, for that matter. Rates on car loans are typcially fixed, so once the loan is made, the rate is guaranteed for the life of the loan, despite the credit of either individual. BUT if the primary person does not pay that particular account on time, it will affect the co-signor's credit score, which may result in having to pay higher interest on other types of loans or possibly even loan denials. A co-signor should always monitor that account to make sure that it's being paid on time to avoid late payments that may have a negative impact on their credit score. visit www.creditscorehero.com and check out the articles on the left side of the page for more information about how credit scoring works.