If no date is set, the benefit must be completed “within a reasonable period of time,” itself determined by the nature of the contract. Concrete Products v Natal Leather Industries is the most important case in determining reasonable time. In this case, the plaintiff agreed to sell to the defendant a large number of steel wedges for suitcases of different sizes. The agreement stipulated that several thousand of all sizes should be delivered weekly and that the order should be considered urgent for small corners. No time has been set for the start of delivery. The applicant did not provide the small corners, although the defendant insisted that the contract be executed. He did, however, send middle corners that were accepted by the defendant in accordance with the contract. Due to the non-delivery of the small corners, the defendant informed the applicant of the termination approximately three weeks after the contract was concluded. In the case of a foreign exchange contract, a creditor is entitled to a full and complete benefit.
There must be strict respect, in other words, 100% power. The principle of reciprocity recognizes that, in many contracts, the common intention of the parties, expressed or not, is that there should be an exchange of benefits. The creditor may therefore refuse any vaguely inappropriate benefit. The power of the component is not a power. Public order does not matter because it represents the public opinion of a particular community at a given time. Public policy considerations are found in legislation, common law, good morality or the public interest. Much of the jurisprudence on performance contra bonos mores involves immoral or sexually reprehensible behavior. Parliament sometimes expressly or tacitly prohibits the conclusion of certain contracts. Since 1994, public order in South Africa has been anchored mainly in the values enshrined in the Constitution. A termination that is exclusively the consequence of a valid contract cannot be invoked in all circumstances. This is an exceptional remedy that is only available if the offence is sufficiently serious or substantial – unless the parties have provided for a revocation clause (a lex commissoria) in the agreement, in which case the agreement prevails over the common law rules. If the offence is minor and there is no lex committed, the innocent party can always count on a determined benefit and claim damages.
The unspoken terms are not expressly agreed upon by the parties, but are nevertheless part of the contract. They are binding on the parties, without expressly agreeing on the points in question. They are generally naturalia and generally involve legal obligations, and in some cases the parties may vary or be excluded, as in a voetstoots sales contract.