Every Muslim can miss a prayer. A person may oversleep, or simply forget. The guidance of the Prophet, peace be upon him, for this situation is short and clear: pray it when you remember it.

Anas reported that the Prophet said that if anyone forgets a prayer, he should pray it when he remembers it, and that there is no expiation for it except to pray it. This is in Sahih al-Bukhari, number five hundred and ninety-seven, and also in Sahih Muslim, number six hundred and eighty-four. He then recited words from the Qur'an. The verse is in Surah Ta-Ha, chapter twenty, verse fourteen, and an English translation of its meaning reads: “Indeed, I am Allah. There is no deity except Me, so worship Me and establish prayer for My remembrance.”

In practice, this means a few simple things. Do not wait for the next time that prayer would normally be prayed. Make it up when you wake up, or when you remember. Pray it with the same number of rak'ahs the missed prayer would have had. And make a sincere intention to guard your prayers in future, asking Allah's forgiveness for any negligence.

These reports speak about sleep and forgetfulness. Other situations involve differences between scholars. For a prayer missed deliberately, the majority of scholars, across the four schools, hold that it must still be made up, together with sincere repentance. A minority hold that a prayer deliberately delayed beyond its time cannot be made up in the same way, and that the person should repent and increase in voluntary worship. The schools also differ on whether missed prayers must be made up in order, and before the current prayer.

If you missed many prayers in the past, scholars generally advise sincere repentance and making the prayers up in a manageable way. Because opinions vary on how to estimate and organise them, speak with a knowledgeable local teacher about your situation.