There is a difference of halachic opinion regarding a Friday night on the date of Tisha B’Av.
Sefardi custom is to permit relations on a Tish’a B’Av that falls out on Shabbat as part of oneg Shabbat.
Ashkenazi custom is to abstain from relations on a Tish’a B’Av that falls out on Shabbat, as a private act of mourning. But even the Ashkenazi practice does not apply when mikveh night falls out on that Friday night, or when fertility issues are involved.
Relations are forbidden on Saturday night and for the duration of the fast. A couple are permitted to resume relations as of havdalah following the fast.
This response was updated on 3 August, 2022.