Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) was asked:
I did not pray until the age of twenty-four. Now with every fard (obligatory prayer) I offer another fard. Is it permissible for me to do that? Should I carry on doing that, or is there something else I have to do?
He replied:
The one who missed prayers deliberately does not have to make them up, according to the correct scholarly view. Rather he has to repent to Allaah, because prayer is the foundation of Islam, and failing to pray is the greatest of sins. In fact, failing to pray constitutes major kufr according to the more correct of the two scholarly opinions, because it is narrated that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “The covenant that stands between us and them is prayer; whoever does not pray is a kaafir.” Narrated by Imam Ahmad and the authors of al-Sunan with a saheeh isnaad from Buraydah (may Allaah be pleased with him).
And the Prophet (peace and blessings of Allaah be upon him) said: “Between a man and shirk and kufr there stands his giving up prayer.” Narrated by Imam Muslim in his Saheeh from Jaabir ibn ‘Abd-Allaah (may Allaah be pleased with him). And there are other ahaadeeth which indicate the same thing.
What you have to do is repent sincerely to Allaah by regretting what you have done in the past, giving up not praying, and sincerely resolving not to go back to it. You do not have to make up anything, either with every prayer or otherwise. Rather all you have to do is repent. Praise be to Allaah, whoever repents, Allaah accepts his repentance. Allaah says (interpretation of the meaning):
“And all of you beg Allaah to forgive you all, O believers, that you may be successful”
[al-Noor 24:31]
And the Prophet (peace and blessings of Allaah be upon him) said: “The one who repents from sin is like one who did not sin at all.”
You have to be sincere in your repentance, and take stock of yourself, and strive to offer prayers regularly on time in congregation. And you have to ask Allaah to forgive what you have done, and do a lot of righteous deeds, and be optimistic, for Allaah says (interpretation of the meaning):
“And verily, I am indeed forgiving to him who repents, believes (in My Oneness, and associates none in worship with Me) and does righteous good deeds, and then remains constant in doing them (till his death)”
[Ta-Ha 20:82]
After mentioning shirk, murder and zina (adultery) in Soorat al-Furqaan, Allaah says (interpretation of the meaning):
“and whoever does this shall receive the punishment.
69. The torment will be doubled to him on the Day of Resurrection, and he will abide therein in disgrace;
70. Except those who repent and believe (in Islamic Monotheism), and do righteous deeds; for those, Allaah will change their sins into good deeds, and Allaah is Oft‑Forgiving, Most Merciful”
[al-Furqaan 25:68]
We ask Allaah to guide us and you, to make our repentance sound and help us to remain constant in doing good. End quote.
Majmoo’ Fataawa al-Shaykh Ibn Baaz, 10/329, 330