Scots contract law governs the rules of contract in Scotland. Contract is created by bilateral agreement and should be distinguished from a unilateral promise, the latter being recognised as a distinct and enforceable species of obligation in Scots Law. The English requirement for consideration does not apply in Scotland, so it is possible to have a gratuitous contract, i.e. a contract where only one of the parties comes under any duties to the other (e.g. a contract to perform services for no consideration). If, however, consideration is given, as for example in a sales contract, the contract is said to be onerous.