Answered by Faraz Rabbani
Question: If one has years of missed prayers, do they need to be made up in order? Or can one first make up all of the missed Fajr salats, then all of the the Dhuhrs, and so on?
Answer: In the Name of Allah, the Benevolent, the Merciful
Walaikum assalam wa rahmatullahi wa barakatuh,
I pray this finds you in the best of health and spirits.
Order doesn’t have to be observed when making up past prayers, if more than six in total. You can make them up in any order. [ref: Shurunbulali, Maraqi al-Falah]
And Allah alone gives success.