A corporate credit rating is an indication of the ability and willingness of a company to repay its debts. Companies and corporations are assigned a credit rating based on a variety of factors. Ratings range from AAA to C or D, according to the rating agency. An AAA credit rating shows that the company has the highest possible credit rating and is a low risk investment. Companies make an attempt to get AAA ratings by reducing their debt and working to improve their overall operation. A low C or D rating may indicate that the company has defaulted and is unable to repay loans.