Global broker Aon is issuing $500m of senior unsecured bonds to repay part of the loan it took out to buy Hewitt Associates.

The new bonds will mature on 27 May 2016 and have a fixed annual interest rate of 3.125%. Rating agency Moody’s has rated the new bonds Baa2. The offering is expected to close on Friday.

Aon took out a $1bn, three-year term loan to help fund the purchase of human resources consultancy Hewitt in October 2010, of which £950m is outstanding. The loan has a variable interest rate of Libor plus 250 basis points – currently 2.71%.