Always get and check the receipt before you part with your money. It should contain the following information:

Seller's name, address and telephone number
Buyer's name and address
Vehicle details (make and model, Vin/chassis number, registration no. date of first registration)
Purchase / sale price

Seller's declaration:
That they have received amount of £......
That the vehicle is theirs to sell.
That any outstanding hire purchase or lease on it has been settled by them.
That the sale is a private sale.

The receipt should be signed and dated.