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Understanding commercial usage: definition, role and application

By Yasmine EDDAM23 April 2025

In the business world, written contracts often seem to govern all relationships. However, beyond the clauses that are negotiated and signed, unwritten rules have a profound influence on day-to-day transactions: these are commercial usages. Often overlooked or underestimated by the uninitiated, they are a source of law in their own right, capable of supplementing, interpreting and sometimes even contradicting the law or the contract itself. For any entrepreneur, understanding their nature and scope is essential in order to secure operations and avoid costly disputes.

This article sets out to demystify trade usages. We will look at their definition, the different categories that exist - from local practices to international standards - their legal force in relation to legal texts and agreements between parties, and finally, the way in which their existence can be proven.

What is commercial use?

Basically, commercial usage arises from repeated practice within a given professional or geographical environment. For a simple habit to achieve the status of a recognised usage, several characteristics are generally required.

Repeated and accepted practice in an environment

Usage presupposes generality the practice must be followed by a significant number of players in the sector or geographical area concerned. It's not just an isolated mania. Secondly, a constance is necessary; the practice must be repeated over time, over the long term, even if the speed of modern exchanges, particularly in e-commerce, can considerably accelerate the formation of new habits.. Finally, the practice must acquire a certain reputation it must be sufficiently well known for professionals in the field concerned to be reasonably expected to refer to it.

Imagine, for example, in the maritime transport sector of a given port city, the constant practice known to all the local players (shipowners, shippers, cargo handlers) of considering that unloading goods systematically includes bringing them to a certain point on the quay. If this habit is sufficiently general, constant and well-known, it could constitute a local custom..

Classical distinction: conventional use vs. legal/customary use

Legal doctrine has long debated the distinction between different categories of use, even if these distinctions are sometimes fluid and their boundaries porous.. The classic contrast is between :

Conventional use (or de facto use) This is a practice used mainly to interpret the will of the parties when a contract is silent or ambiguous. It applies only because it is presumed that the contracting parties intended to refer to it implicitly. Articles 1159 and 1160 of the Civil Code, which invite the judge to interpret agreements by what is customary, refer to this type of practice.
Legal usage (or commercial custom) This would be a genuine rule of objective law, applying even without explicit reference in the contract, simply because it is considered mandatory in the environment concerned (this is the opinio juris seu necessitatisthe belief that it is binding). Passive solidarity between commercial co-debtors (which is not presumed in civil law under article 1202 of the Civil Code) is a typical example of legal usage.

However, the relevance of this distinction is now being debated.. Some authors consider that all commercial usages, provided that they are sufficiently established, constitute rules of law, the difference lying more in the manner in which the judge applies them (of his own motion or by interpreting the will) than in their profound nature.. In practice, a usage can evolve from one category to another as it is progressively recognised by case law..

Modern usage training

The classic image of the spontaneous and almost anonymous emergence of usage no longer always corresponds to contemporary reality.. Today, many uses are actively shaped, formalised and disseminated by professional organisations (trade unions, chambers of commerce, federations).

These organisations develop standard contractsand general terms and conditionsand even codes of conduct or ethics which, while sometimes adopting existing practices, also aim to establish new rules and harmonise behaviour within the profession. These documents, which are widely circulated among members, acquire an objectivity and a force that bring them closer to legal practices, even if they emanate from private initiatives.. The highly structured banking sector is particularly prolific in terms of formalised practices, for example through interbank regulations or the rules governing payment systems..

What are the different types of commercial use?

Commercial practices may have a variable geographical or sectoral scope.

Local use

They are the oldest in history. Their scope is limited to a restricted geographical area: a region, a town, a specific commercial centre, a port, etc.. For example, the precise arrangements for receiving goods at a given portIn the Bordeaux region, for example, silence following receipt of a broker's slip can be considered as a perfect sale. are a matter of local custom. The law sometimes refers to them explicitly, as in the case of commercial leases for the duration of the notice period (article L. 145-9 of the Commercial Code). or to define an appellation of origin ("local, fair and constant usage").

General or national uses

These practices apply throughout France, either across a wide range of commercial activities, or specifically to a given sector but with a national scope..

The most emblematic example of general use is the presumption of passive solidarity between traders jointly liable for the same commercial debt. Unlike civil law, where joint and several liability must be expressly stipulated (article 1202 of the Civil Code), in commercial law it is presumed unless otherwise stipulated, as this facilitates credit and transactions..

Another example is the rebate in commercial sales: in the event of delivery that does not conform perfectly (without the defect being redhibitory), custom often allows a reduction in the price rather than the outright rescission of the sale provided for in article 1184 of the Civil Code.. This practice favours the maintenance of the contract, adapted to the speed of business.

Other uses are specific to a sector but apply nationally, such as theanatocism (capitalisation of interest) quarterly in bank current accounts, which derogates from the rule in article 1154 of the Civil Code requiring a special agreement and a term of one year..

Uses of international trade

With the globalisation of trade, international trade practices have taken on considerable importance.. They make up for the absence of unified international legislation and the diversity of national laws.. Their development is encouraged by the existence of strong international professional organisations and the frequent use of international arbitration.. Arbitrators, who are less bound by national law than national courts, must "in all cases take account of commercial practice" (article 1496 of the French Code of Civil Procedure)..

Attempts have been made to codify some of these usages by bodies such as the International Chamber of Commerce (ICC):

Incoterms (International Commercial Terms) They provide a standardised definition of the respective obligations of the seller and buyer in international sales (allocation of costs, risks, customs formalities) for terms such as FOB, CIF, EXW, etc... Their purpose is to avoid the uncertainties associated with differing local interpretations.
Uniform Customs and Practice (UCP) for Documentary Credits Also published by the ICC, they codify international banking practices with regard to documentary credits, a secure payment mechanism that is essential in international trade. Case law widely recognises their authority, even in the absence of explicit reference by the parties.

These international practices, which are often formalised, form the core of what some call the lex mercatoriaa set of rules specific to the international business community, distinct from national legal systems.

What is the legal force of trade usage?

The central question is how usage relates to other sources of law, principally statute and contract.

Usage and the law

The relationship between usage and the law is complex and depends on the nature of the law in question.

Faced with a law suppletive of will (which applies only in the absence of a contrary intention on the part of the parties) : Usage, whether considered as a rule of law or as the expression of an implicit will incorporated into the contract, generally prevails over suppletive law. For example, the use of the rebate takes precedence over the suppletive provisions of the Civil Code relating to termination for non-performance. The specific rule resulting from professional practice is considered more appropriate than the general legal rule.
Faced with an imperative law (from which the parties cannot derogate) : The general principle is that usage cannot go against a mandatory law (contra legem). In principle, case law refuses to recognise a usage that violates a public policy provision. For example, a local custom cannot take precedence over safety rules or protective provisions of public policy.
Notable exceptions (uses contra legem validated) Despite the principle, case law has validated certain major commercial practices that contradict legal texts, including imperative texts:
- La commercial solidarity goes against article 1202 of the Civil Code (which requires an express stipulation).
- L'quarterly anatocism current account derogates from Article 1154 of the French Civil Code.
- More recently, the banking practice of calculating interest on a 360-day year ("Lombard year") was condemned because it was contrary to legislation requiring reference to the calendar year (365 or 366 days), particularly for calculating the Annual Percentage Rate (APR). This example shows that there is a limit to our tolerance of customary practice. contra legem.

The justification for these historical exceptions lies in the recognised specificity of commercial law and the need to adapt the rules to the needs of commerce, sometimes considering civil law to be subsidiary in this area.. However, this primacy is not absolute and remains subject to the discretion of the courts..

Usage versus contract

Even customs that are considered to be rules of law (such as solidarity or anatocism) are generally not considered to be legal rules. not imperative vis-à-vis the parties. These may expressly exclude the application of a usage by a clause to the contrary in their contract. The clearly expressed will of the parties takes precedence over usage, which often has only a suppletive value..

The difficulty arises when the contract is silent. Does usage apply automatically?

For the recognised legal practices (solidarity, current account anatocism) : Yes, they apply unless otherwise stated.
For the conventional uses (or those whose status is less established): The question of their inclusion in the contract often depends on enforceability.

Enforceability of use

Even established usage does not automatically apply to all parties. Case law makes an essential distinction:

Between professionals in the same business sector or operating in the same marketplace Usage is presumed known and therefore enforceable. It is considered that a professional cannot ignore current practices in his own field. Silence in the face of a contract or situation in which the custom is intended to apply constitutes acceptance of that custom. For example, two wine merchants from Bordeaux are presumed to be aware of local custom regarding the formation of a sale by broker's slip. Similarly, between merchants, prices are generally understood to be exclusive of tax unless otherwise agreed, this usage being presumed to be known.
Vis-à-vis a non-professional (consumer) or a professional acting outside his sector or usual place of business : Use is not not automatically enforceable. It must be proved that the party "outside" the use had a right to it. knowledge and there is agreedThis can be done expressly or at least tacitly (for example, through previous business relationships where the custom was applied). Mere silence is generally not enough. Therefore, a bank cannot impose a banking practice on an uninformed customer without proof of the customer's information and acceptance.

It is interesting to note that while the professional cannot impose an unknown usage on the non-professional, the latter can often take advantage of the usage against the professional, who is supposed to be aware of it..

How do you prove commercial use?

Proof of use raises specific questions, linked to its unwritten nature.

Burden of proof

In principle, as for any legal fact or act, it is the onus is on the party invoking the usage to prove its existence and content. If you claim that a particular usage governs your contractual relationship, it is up to you to demonstrate this to the judge.

However, there are exceptions to this rule:

For the well-known and established legal practices by case law (such as commercial solidarity), the judge is deemed to be aware of them and to apply them ex officio, like the law. The party does not have to prove them.
In the case of practices explicitly incorporated into the law (e.g. statutory notice periods referring to practices), the court must apply them ex officio.
It was even accepted that consular judges (commercial court judges, often from the business world) could share their personal knowledge commercial use without it having been formally proven by the parties, although this practice is less common today.

Methods of proof

In commercial matters, evidence is freely available (Article L. 110-3 of the French Commercial Code).. The existence of a use can therefore be established by any means.

Practice has, however, established a specific method of proof: the motherland. This is a written confirmation generally issued by qualified professional bodies (chamber of commerce and industry, trade union, chamber of trades) or sometimes by legal experts, certifying the existence, content and scope of a usage in a given environment. For example, the Association Française des Banques (now the Fédération Bancaire Française) can issue guidelines on banking practices..

The evidence is not binding on the judge, who has full discretion to assess its probative value.. It may set them aside if it considers them irrelevant or contradicted by other evidence.

Other documents can also be used as proof:

The standard contracts or general terms and conditions widely distributed in a profession.
From professional surveys or collections of practices published.
From testimonials professionals in the sector.
From previous court decisions having recognised the use.

The importance of legal advice on commercial practices

Navigating the world of commercial usages can be complex. Their unwritten nature, the subtle distinctions between their categories, the uncertainties surrounding their enforceability or their relationship with the law make a detailed legal analysis essential.

Calling on the services of a lawyer specialised in commercial law allows you to :

Identify relevant uses What are the practices applicable to your business sector, your geographical area or your international transactions? Are they well established? What is their exact scope?
Secure your contracts When drafting your contracts (general terms and conditions of sale, partnership agreements, etc.), a lawyer can help you to incorporate practices that are favourable to you or, on the contrary, to insert clear clauses to exclude those that could be detrimental to you.
Manage disputes If a dispute arises concerning the application or interpretation of a custom, the lawyer will be able to gather the necessary evidence (request a parer, research case law) and defend your interests before the courts or in negotiation.

Ignoring commercial practices can lead to costly misunderstandings and weakened legal positions. A proactive approach, accompanied by sound legal advice, is the best guarantee.

The complexity of commercial practices and their potential consequences make appropriate legal advice essential. Our firm is at your disposal to help you analyse the impact of trade practices on your business and secure your contractual relations.