Should lawyers use “shall” or “must” in contracts? In modern legal drafting, “must” is generally clearer when expressing an obligation. “Shall” has traditionally been used in contracts, but it can be ambiguous because lawyers sometimes use it to mean different things.
That does not mean you will stop seeing “shall.” It remains extremely common in contracts and other legal documents. For lawyers working in English, the important skill is understanding what “shall” means in context and knowing when “must” provides clearer drafting.
Shall, Must, and May: A Quick Comparison
| Word | Typical use in contracts | Example |
|---|---|---|
| Must | Expresses a clear obligation | “The Buyer must pay within 30 days.” |
| Shall | Traditionally used to express an obligation, but can sometimes be ambiguous | “The Buyer shall pay within 30 days.” |
| May | Usually expresses permission or discretion | “The Buyer may terminate the agreement.” |
For international lawyers, the simplest distinction is: must = obligation; may = permission or discretion; shall requires more care because its meaning can depend on how it is used.
Why the Debate About Shall vs Must Exists
The debate about shall vs must in contracts comes from the history of legal English.
For centuries, lawyers used the word shall to express obligations in contracts and statutes. Many traditional legal documents contain sentences such as:
The buyer shall pay the purchase price within thirty days.
However, modern legal drafting experts have criticized the word shall. They argue that shall is often ambiguous and can have several different meanings.
For example, shall may sometimes mean:
obligation
future action
permission
determination
Because of this ambiguity, some courts have interpreted shall differently depending on the context.
As a result, many lawyers now prefer the word must when drafting obligations in contracts.
The Traditional Use of “Shall” in Contracts
Historically, shall has been the standard word used to create obligations in legal documents. Many contracts and statutes still contain this traditional drafting style.
Example:
The tenant shall maintain the property in good condition.
In this sentence, the word shall creates a legal obligation.
However, the problem with shall is that it can sometimes be interpreted differently depending on context. In ordinary English, shall is rarely used in modern speech. Because shall is uncommon in modern everyday English, its legal uses can be especially confusing for non-native English speakers.
The Modern Preference for “Must”
Many modern drafting authorities now recommend using must instead of shall to express legal obligations.
Example:
The tenant must maintain the property in good condition.
In this sentence, the obligation is clearer. The word must directly expresses a requirement.
Modern legal drafting guidelines often recommend must because it expresses an obligation more directly and is less likely than shall to be confused with other meanings.
For lawyers writing contracts in international contexts, using must can reduce confusion and improve clarity.
Why Ambiguity Matters in Contract Interpretation
Contract language is interpreted in context and under the applicable law. A word such as shall does not necessarily operate in isolation; its meaning can depend on the surrounding clause, the agreement as a whole, and the governing jurisdiction.
That creates unnecessary uncertainty when the drafter simply wants to impose a duty. Using must for obligations can make the intended meaning easier to identify.
For international lawyers, this is an important distinction: when reading an existing contract, consider what shall means in context. When drafting a new obligation, clearer wording can reduce the possibility of misunderstanding.
Advantages of Using “Must” in Contract Drafting
Many modern drafting authorities recommend using must rather than shall when the intention is to impose an obligation.
1. Greater clarity
The word must clearly expresses obligation.
Example:
The licensee must pay royalties within 30 days.
This language is easier to understand.
2. Simpler language
Plain English drafting encourages simpler and clearer language. Using must instead of shall aligns with modern drafting practices.
3. Easier for international readers
Many contracts today are used in international business environments. Lawyers, businesspeople, and regulators may all read the contract.
Using must instead of shall makes contracts easier for non-native English speakers to understand.
Situations Where “Shall” Is Still Used
Although modern drafting experts often recommend must, the word shall still appears in many legal documents.
For example:
- older contracts
- traditional law firm templates
- statutes and regulations
In some legal systems, statutes frequently use shall to create mandatory rules.
Because of this, lawyers must still understand how shall is used when interpreting legal documents.
Best Practices for Contract Drafting
When deciding how to address shall vs must in contracts, many lawyers follow several best practices.
Use “must” for obligations
Example:
The supplier must deliver the goods by the delivery date.
Use “may” for permission or discretion
Example:
The buyer may terminate this agreement upon written notice.
Avoid unnecessary complexity
Clear and simple language reduces the risk of disputes.
Maintain consistency
Use modal verbs consistently throughout the contract. If must expresses obligations and may grants permission or discretion, apply those choices consistently.
Consistency is one of the most important principles of effective legal drafting.
Examples Comparing Shall and Must
To understand the difference between shall vs must in contracts, consider the following examples.
Traditional drafting:
The contractor shall complete the work by July 1.
Modern drafting:
The contractor must complete the work by July 1.
Both sentences express obligation, but the second version is clearer and more consistent with plain English drafting principles.
Practical Advice for International Lawyers
International lawyers often work with contracts drafted by lawyers from different countries, firms, and legal traditions. As a result, you are likely to encounter both shall and must.
When reading a contract, do not automatically assume that every use of shall performs exactly the same function. Read the entire clause and consider whether the language creates an obligation, describes a future event, grants a right, or serves another purpose.
When drafting in English, clarity should generally take priority over traditional legal style. Must is often the clearer choice for an obligation, while may normally indicates permission or discretion.
At the same time, do not automatically replace every instance of shall in an existing document. Law-firm templates, client requirements, governing law, and established drafting conventions may affect the language you should use. Consistency within the document also matters.
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Related Legal English Articles
- Contract Terminology Demystified: Break Down Essential Contract Terms and Clauses
- Legal Drafting: Crafting Clear and Persuasive Legal Documents in English
- Shall vs. Will: Navigating the Language Maze in Everyday English and Legal Contexts
- Contracts in Common Law vs. Civil Law: Guide for ESL Lawyers
Final Thoughts
The choice between shall and must reflects a broader movement in legal drafting toward clearer and more precise language. When creating an obligation, must is often the clearer choice, while may generally indicates permission or discretion.
International lawyers must still understand shall, however, because it remains common in contracts, statutes, and established legal templates. The goal is not simply to avoid traditional language, but to understand it and choose wording that communicates the intended meaning as clearly as possible.
Legal English Lexicon
Ambiguous
Language that can be interpreted in more than one way.
Clause
A specific provision or section of a contract.
Contract drafting
The process of writing legal agreements.
Discretionary
Allowing someone to decide whether or not to act.
Enforceable
Legally valid and capable of being enforced by a court.
Obligation
A legal duty to perform a certain action.
Plain English
A style of writing that uses clear and simple language.
Provision
A rule or clause contained in a legal document.
Statute
A law enacted by a legislature.
Interpretation
The process of determining the meaning of legal language.
