My holding came as 10 acres in a single field. I promptly divided it in 4 and more recently added a 'corridor' paddock to make moving stock easier between barn and back fields, aswell as using it for feed rings in winter to reduce poaching in the adjacent field (which is behind my neighbours' kitchen window!).
Nothing notified as the original marches remain intact, it's just subdivision of existing land. But I noticed after a few years the new fences appeared in the new issued holding map and in plans used by the Hydro to record/plan overhead power/poles for wayleaves, so I assume there isn't an issue (in Scotland).