Is the expiation for delaying the making up of Ramadan fasts an obligatory, a necessary, or a recommended act, and is it permissible to postpone it until money is available?

The fidyah is obligatory for whoever delays making up for Ramadan without a valid excuse until the next Ramadan begins. This is the opinion of the majority of jurists. As for whoever delays it due to an excuse, there is no fidyah upon them by agreement. It is permissible to give the fidyah before or after making up the fast. There is no fidyah upon one who is ignorant of the impermissibility of delaying the make-up fast.