If you show in usef shows you will need your horse microchipped
I do unaffiliated showjumping in the uk and I’ve never needed one, only once just needed my passport to prove ownership I think it was
For lower level shows like 4h or open shows no. But if your showing upper level you may need to.
You mean a registration chip? In my country all horses need to be chipped in order to check if your horses documents are legitimate, you get a huge fine if it isn't chipped, even when you are just transporting the horse from one barn to another. The chip is needed to check if it is the correct horse, horse has all vaccinations, show results, and so on. By that rule all horses competing in shows have to be chipped. Here you have to register your horse at the show federation if your horse has never been shown before, and all you have to do is send them the chip number because that registers all information needed. But there is no seperate registration necessary in order to show.