Hi there, the vat should be calculated at the difference between the sale price and the cost price. i.e. profit element, and this profit element will be the VAT inclusive price. Example Sale of £1000 and purchased at £800 = £200 profit the vat is inclusive of the £200. It is worth have a looking on HMRC rules etc regarding this scheme on their website as very accurate records need to be kept relating to the purchases and sales.
Hi Sarah, no I do not think you have to be signed up, HMRC website states
'You don't need to fill in an application form to join a scheme and you can start using it at any time'
I think the key point to remember is to work out the records/evidence that HMRC need you to keep, and the rules they stipluate.
I am doing a VAT diploma so it is refreshing my mind on things as well. My course provides a good summary sheet on it if you would like me to email it to you, just let me know your email address.