Is it obligatory to make up all fasting days missed due to menstruation before the next Ramadan, or is it permissible to postpone some of them until after Ramadan?

You must make up for the fasts you missed from previous Ramadans and the last Ramadan before the upcoming Ramadan begins. Whoever delays making up the fasts without a valid excuse until the next Ramadan begins, must, in addition to making up the fasts, offer an expiation of feeding one poor person for each day. This expiation does not multiply with the entry of other Ramadans. The make-up fasts should be performed in order for the previous Ramadans, then the last Ramadan. So, you make up the days of the first month, then the second, and so on. However, if you do not observe this order, it is sufficient according to some jurists.