If there is an enforceable agreement – a contract – the terms of the contract are important when a party has allegedly broken the agreement. The terms of a contract are what has been promised. However, it is for the Andean courts to interpret the evidence of what the parties said before the contract was concluded and to interpret the agreed terms. The construction of the contract begins with the explicit promises that people make to each other, but also by terms contained in other documents or opinions that should be taken up. The general rule is that proper communication on this concept is necessary and that more attention should be paid to a dependent concept. The meaning of these concepts must then be interpreted and the modern approach is to interpret the meaning of an agreement from the point of view of a reasonable person with knowledge of the context as a whole. In addition to legislation, courts may also include conditions in contracts in general to „fill in the gaps“ where necessary to meet the reasonable expectations of the parties or if necessary for incidents in certain contracts. English law, particularly at the end of the 19th century, had complied with the principle of laissez-faire „contractual freedom,“ which allows people to accept the terms they wished in the general law of contracts. On the other hand, specific contracts, particularly for consumers, employees or tenants, have been established in such a way as to carry a minimum core of rights, most often arising from the law, which aim to ensure the fairness of contractual conditions.
The evolution of jurisprudence in the 20th century generally shows an increasingly clear distinction between general contracts between commercial parties and unequal bargaining contracts, because in these trading groups the real choice is hampered by the lack of real competition in the market. As a result, certain clauses in the statutes, such as the Contract Contracts Act 1977 and Part 2 of the Consumer Rights Act 2015, may be found to be abusive and may be removed by the courts with the assistance of the Competition and Market Supervisory Authority. When a contract is formed, good thinking is required and a free promise is therefore not binding. However, the review must be of sufficient value in the eyes of the law, but it must not reflect a reasonable price. Proverbially, you can sell a house for as little as a peppercorn, even if the seller „doesn`t like pepper and throws corn.“  This means that courts generally do not question the fairness of trade unless there is legislation or (in certain contexts such as consumers, employment or leases) two parties with unequal bargaining power.  Another difficulty is that the consideration for a deal was not given if the given thing was an act that was done before the promise, such as the promise to make a loan for money already used to educate a girl.  In this situation, the courts have long been willing to assert that the case that was made was implicitly based on the expectation of a reward.  Major problems arise when contractors wish to change their conditions.
The old rule that preceded the development of protection in the law of economic constraints was that if a party merely promises to fulfill an obligation it had already assumed against a higher price, there is no contract.  In the principal, Williams/Roffey Bros. Nicholls (Contractors) Ltd. the Court of Appeal, however, stated that it was more willing to interpret someone who essentially had to give what he had to do before he considered the new agreement if he granted „practical utility“ to the other party.  When Williams, a carpenter, was promised by Roffey Bros, the owner, to more money for the term work, it was found that Roffey Bros. would avoid a penalty clause for the late execution of the contract, would eventually avoid the cost of litigation and would have a slightly more reasonable, sufficient payment mechanism.