I've just taken on a husband and wife team who have recently gone from him and his wife trading seperately as Sole Traders, to a formation of one Ltd company. (He is in IT Support, she as Admin / Office support, so the businesses are kind of 'interlinked', and they are advertising as a 'backroom support' for small businesses)
Individually, they were both under the VAT threshold in their respective Sole Trader roles, however, if you combine both their turnovers for last 12 months, it brings them slightly over the VAT limit. Therefore, do they need to register for VAT now, (IE taking into account their turnover as Sole Traders) or do you just look at what they are now bringing in via the Ltd comp, and register for VAT when the Ltd comp turnover gets towards the VAT mark?
I've never had anything like this before, so don't want to leave registering if they should be doing it now...
Having ruled out the possibility that there was always one business, you should just follow the normal turnover rules starting with formation of the new entity.