Assuming we're talking cars, not commercials, VAT is payable on first purchase. Subsequent, secondhand sales do not show VAT on the invoice and VAT is not charged to or paid by the buyer*
But - the dealer pays VAT on his margin to HMRC. He can't itemise it on the invoice because he can't charge it
So if a dealer buys an SLS for £100k and sells it for £110k he has to write a cheque to HMRC for £2k!
Oh the joys of being a motor trader!
* You'll see some cars, particularly at auction, quoted as being VAT qualifying. I have no idea what the explanation is
Nick Froome
the independent Mercedes Estate specialists