Their experts look into a company's scenario and figure out a bond rating for the company. Every rating service has its own formula for measuring threat and its own type of rating scale. Normally, score scales are defined in letter grades, where an AAA rating designates a safe, low-risk bond, and a D rating designates a high-risk bond.government bonds, are generally low-yield bonds. You can depend on getting a payout however that payout will be small. what a bond in finance. On the other side of the spectrum, you have what's not-so-affectionately called, which are low-rated, high-risk bonds. In order to lure financiers into buying these risky junk bonds, the issuing business guarantee high yields.