Well, that doesn't help me - we were planning to have a 'spring ball' and one in the autumn too, both at the same place.
Customs and Excise' s definition of 'one-off' is different to most. This means that you can hold 15 events of the same kind in the same location in any financial year and still be exempt from VAT.
But as soon as you hold 16 events of the same kind in the same location, then you have to pay VAT on all of the income from all of the events.