For example, when negotiating a letter of intent or heads of terms, it is a useful way of making it clear that, although the key terms of the transaction are being put in writing, neither party intends to be legally bound unless and until those terms are then confirmed in a more formal, detailed agreement. And anyone who has bought or sold a house in the UK will be familiar with offers being 'subject to contract' (or 'STC'), making it clear that, although an offer to purchase a property may have been accepted by the seller, there is no commitment to proceed with the transaction until the parties exchange contracts.