Some terms are in a contract because the law will not leave them out

The agreement is always longer than the document

Two people agree a price and a date, shake hands, and believe they have settled everything that matters. They have settled almost nothing. Any arrangement of even modest complexity carries dozens of questions nobody raised — what happens if delivery is late, who bears a defect that appears in the second month, whether the work may quietly be handed to somebody else — and a decision-maker asked to resolve a dispute has to answer them somehow.

Rather than treat such an agreement as too incomplete to enforce, most systems fill the gaps. Terms that were never spoken are treated as part of the bargain, either because the parties would obviously have agreed them or because the law attaches them to that kind of contract whatever the parties thought. The vocabulary differs between traditions. The practical effect does not: the contract you are in is wider than the contract you read.

Gap-filling arrives from more than one direction

One route looks at the particular bargain. If a term is so necessary that the arrangement makes no commercial sense without it, or so obvious that both sides would have brushed the question aside as not worth stating, many common law systems will read it in. The threshold is deliberately high, because a court that improves a bargain has stopped enforcing it and started rewriting it, and judges are conscious of that line.

The second route ignores what these particular parties intended. Certain terms attach to a category of contract — sale, hire, employment, letting — as a matter of policy, so that everyone dealing in that category deals on a known minimum. Several civil law systems reach comparable ground through a general duty of good faith in performance, which does work that common law systems distribute across several narrower doctrines. The routes are different and the results are not identical, though they overlap far more than the theory suggests.

The ones that cannot be drafted away

In consumer dealings the implied terms matter most, because that is where systems most often make them compulsory. Goods generally have to correspond with how they were described, be of a quality a reasonable person would accept, and be capable of the ordinary purpose such goods serve. Services generally carry an obligation of reasonable care and skill. A clause purporting to remove those in a consumer sale is commonly ineffective, and in some places it is itself unlawful to include.

Between two businesses the picture loosens considerably. Many systems permit sophisticated parties to allocate risk as they like, subject to some control over the most extreme exclusions, while others police business contracts almost as firmly as consumer ones. That divergence is one of the reasons a clause struck out in one country operates perfectly well in another, and it is why the same standard form is redrafted for each market a company sells into.

Custom and past dealing can bind a newcomer

Where two parties have contracted repeatedly on the same terms, those terms can be treated as carrying into the next transaction even though nobody restated them. That is convenient for people who deal with each other constantly and awkward for anybody whose earlier dealings happened on terms they have forgotten about.

A trade custom can operate the same way, and it catches newcomers. Someone entering an unfamiliar industry may find that a settled practice in that market is treated as part of their bargain although they had never heard of it. Systems that recognise this generally require the practice to be well known, consistent and reasonable before it binds anyone, so an assertion that everybody does it this way is a long way short of proof. It remains a real hazard when a first contract in a new sector is negotiated informally.

A clause saying the document is everything does not clear the field

Standard forms often declare that the written agreement contains the entire understanding and that nothing said beforehand forms part of it. Such clauses do useful work against prior statements and negotiations, and in many systems they are given considerable weight between commercial parties.

What they generally cannot do is displace a term the law imposes. An obligation attached to a category of contract by statute or by mandatory rule sits outside the parties’ control, so the fight moves elsewhere — to whether an exclusion of liability is permitted, whether it was properly incorporated, and whether the buyer was dealing as a consumer at all. That last question decides more disputes than its dullness suggests, and it turns on facts rather than on labels.

Where the general picture stops being useful

Which terms are implied, how firmly they are protected, and what remedies follow a breach of one all differ by jurisdiction, and the consumer and business positions can diverge sharply within a single system. Nothing here is advice about a particular contract, and it could not be, because the answer depends on local rules and on facts a general article cannot see.

If a term you are relying on was never written down, get advice early rather than after a long exchange of letters. A limitation period usually applies to contract claims, it can be shorter than people expect, and complaining to the other side does not normally pause it. Correspondence is not a substitute for finding out how much time you actually have, and that question can be answered cheaply while the others are still open.