Is it obligatory for someone who has repented and started praying to pay Zakat on money saved from past years in which they did not pray, and is Zakat waived for someone who did not pay it for several years and then spent the money and no longer possesses it?

Prayer is a great pillar of Islam. Whoever misses prayers must make up for all the missed ones if he knows their number. Otherwise, he should continue making them up until he is reasonably certain that he has fulfilled his obligation. Zakat is also a pillar of Islam, and it must be paid for all past years. If one is unable to pay it now, he should pay it when he becomes able. Scholars have differed regarding the ruling on one who abandons prayer without denying its obligation. The majority of them do not consider him a disbeliever, while some consider him a disbeliever and outside the fold of Islam. According to the latter view, he is not obliged to make up for the missed prayers or zakat; rather, he must repent and renew his faith.