Qadhaa salaah is Pending when the Jamaa'ah stands up to perform the salaah

Q: Salaah-490: A person had not yet performed the Zuhr salaah when the Jamaa'ah stood up for the Asr salaah. Should I perform the Qadhaa of Zuhr before joining the Jamaa'ah or not?

Answer: If the person is Saahibut Tarteeb (a person who missed no more than six salaah from the time he came of age to the present day), he should perform the Zuhr Qadhaa first. If he is not a Saahibut Tarteeb, he should first join the Jamaa'ah for Asr and then perform the Qadhaa of Zuhr.

Fatawa Rahimiyyah vol.2