If a person delays making up for missed Ramadan fasts for several Ramadans, is he obligated to fast them immediately and consecutively, or is he permitted to fast them intermittently until the following Ramadan, and is it permissible to fast six days of Shawwal or voluntary fasts before making up for the missed fasts?

Whoever delays making up for missed days of Ramadan (definition) until another Ramadan begins, must make up those days after the second Ramadan. Furthermore, expiation (kaffara) is incumbent upon them if the delay was without a valid excuse. It is best to hasten in making up the missed days and to do so consecutively to clear one's obligation.

The make-up days for Ramadan should be prioritized over fasting the six days of Shawwal, because making up missed days is an obligatory act, while fasting the six days is a voluntary act. The obligatory act takes precedence. If one fasts the six days of Shawwal before making up for missed days, their fast is valid, but it is contrary to what is most preferable.