If a person comes when the Funeral Salaat is going on, that person should not join in the middle. Instead, that man should wait for the imam to say a Takbeer and should join in saying the Takbeer along with the imam. When the imam ends the Salaat with Salaam, then this man should not end the Salaat but should perform the missed Takbeer and then end the Salaat with Salaam.
As given in Noor ul Idhaah ma’a Haashiya Tahtaawi, Pg. no. 593/594.
And Allah Most High knows best.
Mufti Syed Ziauddin Naqshbandi Qadri
[Shaykh ul Fiqh, Jamia Nizamia,
Founder-Director, Abul Hasanaat Islamic Research Center]