This is a part payment of the agreed purchase price paid by the buyer on exchange of contracts. Most contracts provide for the buyer to pay 10% of the purchase price. If you feel you will be unable to pay a full 10% deposit you must let your conveyancer / solicitor know at the beginning of the purchase process so that they can try to make other arrangements for you. This can frequently be arranged, especially where there is a chain of transactions involved. In the very rare event that a buyer backs out of the purchase after exchange of contracts, the full 10% would be forfeited.