Answered by Ustadh Tabraze Azam
Question: I started praying 5 times daily when i turned 15. How many years of qada should i make up now?
Answer: Assalamu alaikum wa rahmatullahi wa barakatuh,
I pray that you are well, insha’Allah.
If one has been praying since puberty, one does not have to make up any prayers. [Shurunbulali, Maraqi al-Falah]
One becomes responsible for performing the prayer after puberty. This is established for males by having a wet dream, or females by menstruation. If neither occurs, it is considered from when one reached 15 (lunar) years.
If one cannot remember, one should make a reasonable estimate of the number of prayers one missed, and then strive to make them up, consistently.
Please also see: Estimating the Number of Make-Up Prayers
And Allah alone gives success.
Checked & Approved by Faraz Rabbani