Coupon tells us the rate of returns(%) for the bonds when it was first issued based on issue price. Yield tells us the rate of returns(%) for the bond based on current price. Assuming a bond was issued at $1000, promising to pay $50 yearly, it has a coupon rate of 5% & yield of 5%. However, if due to unforseen circumstances the bond price drops to $500, it still has a coupon rate of 5% but the yield is currently 10%. Coupon (%) = Returns / Issue Price * 100.