What level do start wearing the shadebelly coats for dressage?

Hi everyone!

At what level do event riders start wearing the shadebelly coats for the drassage phase? Is it only the highest level, Advance?(That's what it's called right? Lol)
For some reason, this question came across my mind the other day and I got curious......

No one at all?

I've seen people use them at the Intermediate/CCI* levels but no lower than that

That would make sense

Intermediate and Advanced usually. However my sister did a CCI* at preliminary level and although it was not required, she was told that many would be wearing them so she bought one anyway. There were a few wearing normal coats but most wore a shadbelly. So I guess intermediate, advanced and anything with a star prelim and up.

For the most part any event where FEI rules govern (CCI*, CIC*, CCI**, CIC**, CCI***, CCI****) you'll see people wearing them. Though I believe they're not required until advanced.