Their experts investigate a company's scenario and figure out a bond ranking for the business. Every ranking service has its own formula for determining threat and its own sort of rating scale. Typically, score scales are defined in letter grades, where an AAA ranking designates a safe, low-risk bond, and a D rating designates a high-risk bond.federal government bonds, are normally low-yield bonds. You can depend on getting a payout however that payout will be small. what is bond rating finance. On the other side of the spectrum, you have what's not-so-affectionately referred to as, which are low-rated, high-risk bonds. In order to lure investors into buying these risky junk bonds, the providing companies promise high yields.