An interest rate swap in which the floating rate is set in arrears. This means, the floating rate is determined based on the value or level of a specific reference rate at the end of the reset period. Once defined, the rate is applied backwardly or retroactively to that period.

The back-set swap has several other names including: in-arrears swap, swap-in-arrears, arrears swap, LIBOR in-arrears swap, reset swap, delayed reset swap, and back end set swap.