I don't know if this is special to our agency, or if it's something that happens all over?
We are probably matched with an adoptive child - finally, it's been a long slog.
I'm planning to take adoption leave, and as part of that I need to tell my employer about the match - with the placement date, official in-writing notice that I've been matched, and a copy of the matching certificate. This seems to be very standard, it's in the government guidelines at https://www.gov.uk/adoption-pay-leave/how-to-claim
However - we aren't officially matched until we've been to panel, then had them make a recommendation to the ADM, then they approve the match. And at that point, we want to do introductions as soon as possible.
So I can't actually give my employer anything in writing until the ADM decision - but I want to start leave, as permitted, 14 days before placement, which means I can't really give my employer the "official" date until just before I stop work, if that.
My work are thankfully very understanding and supportive, but goodness knows how people handle this if they don't have a supportive employer!