Son leaving College and Universal credit

[Imissthesummer]

My son will be leaving college this summer and hoping to get a apprenticeship. When do I tell universal credit. His last day in college? or 31 August? Thanks

Officially they remain under full time education until Aug 31st. UC will ask whether your child is continuing in full time education at some point, so will CB.
Personally I'd be telling them on the date he starts the apprenticeship to cover yourself