Q: Is it permissible or not to perform Tahajjud with Jamaah (congregation) during Ramadan?
A. If it is not formally organised, people are not invited to it and there are one or two people with the Imam in the Jamaat, it will be permissible, otherwise Makrooh. This will apply in and out of Ramadhaan.
Moulana Yusuf Laher