Is it compulsory after sex before making seheri?

It is not compulsory to engage in sexual activity after having sex before making Sehri (the pre-dawn meal during Ramadan). However, if a couple has had sexual relations during the night, they should perform Ghusl (ritual purification) before they can pray or fast. The key requirement is to ensure that one is in a state of ritual purity for the fast to be valid.