Question: What is the ruling regarding a Muslim who had not fasted (during the month of Ramadhaan) for many years, despite carrying out the other obligatory acts of worship upon him? Knowing he had nothing hindering him from fasting, does he have to make up that which he has missed if he makes repentance?
Response: That which is correct is that he doesn’t have to make up that which he has missed if he makes repentance. This is because all acts of worship are enjoined upon the believers at stated times. So, if someone intentionally delays any of them, such that the time passes without a (valid) reason, Allaah (subhaanahu wa-ta’aala) will not accept this act from him. So based upon this, there is no point in making up that which he missed. However, he should make repentance to Allaah (‘azza wa-jall) and increase in doing good actions and one who seeks forgiveness, Allaah forgives him (inshaa’Allaah).
Shaykh Ibn ‘Uthaymeen
Fataawa Ramadhaan – Volume 2, Page 556, Fatwa No. 539;
Fataawa ash-Shaykh Muhammad as-Saalih al-‘Uthaymeen – Volume 1, Page 536.fatwaonline.com