Weather the bond is issued at a premium or discount or at par, the interest payable (in cash) is calculated the same way:
Face value (principal) of the bonds times coupon (contractual interest rate).
The market price of a bond issues at a premium is equal to the present value of its principal amount and-
The present value of all future interest payments, at the market(effective) interest rate.
If electing fair value option for valuing bonds payable
The fair value of the bond and the principle obligation value must be disclosed