If a person did not do their prayers in the past and now they want to commit to their faith and prayers, do they have to make up all the missed prayers for the previous past years?

Some scholars believe if the person missed the prayers in the past with no excuse, out of laziness and carelessness, It is not valid for him to make it up. Rather he has to repent and regret it and resolve not to do that again, and he should do a lot of good deeds and offer a lot of voluntary prayers to make up for the past negligence of prayers.

Allah says (what can be translated as):
“Verily, As‑Salaah (the prayer) is enjoined on the believers at fixed hours”
[al-Nisa’ 4:103]

The majority of scholars believe that he has to make it up. They compared this case as an analogy with the one who forgets or falls asleep, and they said that if the one who forgets has to make it up, then it is more likely that the one who deliberately omitted it should do so.

The Prophet (peace and blessings of Allah be upon him): “Whoever forgets a prayer, let him offer it as soon as he remembers, for there is no expiation for it other than that.”

Allah Knows Best