Q. If a latecomer joins the Imaam in the sitting position of Tashahhud and then the Imaam makes Salaam, does the latecomer have to sit for a period of time before making up his missed Rakaats?
A. A latecomer (Masbooq) should recite the Tashahhud if the Imaam completes the Salaah before standing up to perform his missed Rakaat/s. However, if a latecomer does not recite the Tashahhud entirely or partially after the Imaam completed the Salaah, the Salaah will still be valid. (Shaami 1/496)
Allah Ta’ala Knows Best
Mufti Ismaeel Bassa
This answer was collected from TheMufti.com, which is a fatwa portal managed by Mufti Ismaeel Bassa from South Africa.