Must the missed days of Ramadan be made up before the advent of the next Ramadan?

The days you missed in Ramadan must be made up before the next Ramadan, according to the majority of scholars. If you delay making them up until the next Ramadan without a valid excuse, you have sinned, and in addition to making them up, you are obligated to pay the Fidyah, which is feeding one poor person for each day you delayed making up.