Answered by Ustadh Tabraze Azam
Question:As salaamu alaykum,
If someone has been reading a letter of the Fatiha incorrectly for some time but is not sure how long does he need to repeat all his past prayers?
Answer: Wa alaikum assalam wa rahmatullah,
I pray this finds you in the best of health and faith, insha'Allah.
No, you do not need to make up any prayers.
Please also see: Do Grammatical and Pronunciation Mistakes While Reciting the Qur’an Invalidate Your Prayer?
And Allah knows best.
Checked & Approved by Shaykh Faraz Rabbani