Sahw of Ma'mums in Salah

Q: If someone comes to offer Salah (Prayer) in congregation, but they only catch one or two Rak`ahs (units of Prayer) with the Imam (the one who leads congregational Prayer), and after that they conclude their Salah alone, but forget to perform the Rak`ahs they missed or they have doubts about their Salah, is it permissible for them to perform Sujud-ul-Sahw (Prostration of Forgetfulness) or not?

A: If the Ma'mums (persons being led by an Imam in Prayer) forget to offer the Rak`ah they missed or are doubtful about their Salah, they have to continue offering the Salah based on the least actions they are sure that they have performed, and then perform Sujud-ul-Sahw.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.