Ensure you get the calf in a trailer or pen, away from mother, before tagging.
Highlands can be the most placid of beasts, until the mother hears the bellow of her captured calf. You cannot safely tag a calf with its mother, complete with 5ft hornspan, breathing down your neck.
I shall remember forever the news report, many years ago, of a woman who went to examine her newborn highland calf and ended up with a highland horn through her eye socket.