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.
In particular, a declaration of intention, a testamentary provision, and an offer will not be a promise.
At common law, a promise had to be proved by writ or oath.
However, after the introduction of the Requirements of Writing (Scotland) Act 1995, a promise need only be evidenced in writing for: A Contract is formed by the acceptance of an offer; an offer can be constituted by responding to an invitation to treat.
This act includes damages for breach of contract of sale.