It is highly recommended to join congregational prayer from the beginning.If someone however misses a Rak’ah, he is regarded as a Masbooq and has to complete his Salah after the Imam completes his Salah. It is common practice for a Masbooq to stand up to complete his prayer after the first Salam. This Fatwa clarifies that a Masbooq should stand up after the second Salam of the Imam.
To read or download click on the following link: Should masbuq stand up after the first or second salam
