what is investment grade 
an investment grade is a rating that signifies a municipal or corporate bond presents a relatively low risk of default bond rating firms like standard poor s s p moody s and fitch use different designations consisting of the upper and lower case letters a and b to identify a bond s credit quality rating aaa and aa high credit quality and a and bbb medium credit quality are considered investment grade credit ratings for bonds below these designations bb b ccc etc are considered low credit quality and are commonly referred to as junk bonds 1investopedia tara anand