DavidJN - I don't believe it's the accrued interest. When I set the settlement date to September 1, 2017 (which is a coupon payment date) and apply the following formula: =((1+(YIELD(DATE(2017,9,1), DATE(2028,9,1), 0.0475, 102.1277994 , 100, 2, 1) /2)) ^2) -1 I get a yield of 4.5532798%, whereas Bl...