Half a Promise: Why Effort Clauses Need a Standard, Not an Adjective

A contract is signed in good faith. One party undertakes to use its reasonable endeavours to secure a planning consent, obtain a regulatory approval, or land a particular customer. Nothing happens. The other party protests that the promise was broken; the promisor replies that it tried. Both are sincere, and the argument that follows is one of the most common — and least necessary — disputes in English commercial life.

The difficulty is rarely dishonesty. It is that the parties never agreed what 'trying' looks like. They chose an adjective and moved on, leaving the standard to be reconstructed years later by lawyers reading old emails.

Three phrases, three weights

English law does not attach fixed, dictionary meanings to these formulas. The court construes the clause in its contract, in its commercial context. But the adjectives are not interchangeable, and the broad hierarchy is well understood.

Best endeavours is the most onerous. In Jet2.com Ltd v Blackpool Airport Ltd [2012] EWCA Civ 417, the Court of Appeal considered an obligation on the airport to use best endeavours to promote the airline's business. The court held that this could require the airport to prioritise the airline's flights even where doing so cut against its own financial interests, subject to the limits of practicality and safety. That is a demanding standard: it may oblige a party to act against its own commercial advantage.

Reasonable endeavours sits at the other end. It generally requires the promisor to take a reasonable course of action, but allows it to weigh the obligation against its own commercial interests and to choose between several sensible options. In Rhodia International Holdings Ltd v Huntsman International LLC [2007] EWHC 292 (Comm), the court treated a reasonable endeavours obligation as a duty to take reasonable steps, and confirmed that whether the promisor must sacrifice its own interests is a question of construction — usually answered in the negative.

All reasonable endeavours falls between the two. Little v Courage Ltd (1995) suggested it should be treated as equivalent to best endeavours, at least so far as spending money is concerned; later authority has tended to place it in the middle, requiring more than reasonableness alone but stopping short of outright self-sacrifice.

What none of these phrases does is guarantee the outcome. An efforts clause is a promise about process, not result. If the parties wanted a guaranteed consent, approval or contract, no adjective would have delivered it.

What the court will not do

The court will not write the clause for the parties. In Astor Management AG v Atalaya Mining plc, an obligation to use reasonable endeavours to agree a deferral of consideration was held too uncertain to enforce, because it amounted in substance to an agreement to agree. Nor will a judge invent the steps, the timetable or the budget that the parties omitted.

What the court will do is ask a practical question: in the circumstances that actually arose, was what the promisor did — and what it declined to do — a reasonable response to the obligation it accepted? That question is answered on the evidence, and the evidence is almost always documentary.

Proving an effort

An effort clause is won or lost on records. A promisor that genuinely tried but kept no record of trying is in a materially weaker position than one that documented its reasoning. A beneficiary that never asked for an update will struggle to show that the promisor fell short.

In practice, the following material tends to decide these arguments:

• A decision log. What steps were considered, what they would have cost, and why each was discounted. Contemporaneous reasoning is persuasive; reconstruction after the event is not.
• Resource allocation. How the project was staffed and funded relative to the promisor's other commitments. An effort clause met with a single email and no budget is hard to defend.
• Alternatives explored. Whether realistic routes were tested, including those the promisor found inconvenient.
• Correspondence with the beneficiary. Regular updates, requests for information and warnings of difficulty all support the case that the obligation was being actively managed.
• Consistency. How the promisor treated comparable obligations for other counterparties.

Silence is not an effort. Where the clause includes a consultation or reporting requirement, treating it as a formality will undermine the substantive defence.

Drafting obligations that mean something

Most of these disputes are avoidable at the drafting stage. A well-constructed clause answers five questions.

What is the objective? State the outcome precisely — the consent, the milestone, the contract — rather than a general aspiration to pursue opportunities.

What must be done? Itemise the steps expected: which applications, which approaches, which approvals, by when. A list converts an adjective into an auditable standard.

Whose money, and how much? Say whether the promisor must incur cost, and whether there is a cap. Silence invites argument about whether expenditure was required at all.

Whose interests prevail? If the obligation may conflict with the promisor's other commercial interests, address that expressly rather than leaving it to the choice of adjective.

What happens if the objective is missed? A consequence — a termination right, a price adjustment, a step-in right, a defined damages measure — gives the clause teeth and reduces the incentive to litigate the standard.

Two further points repay attention. First, avoid stacking adjectives or adding carve-outs such as 'subject to the promisor's commercial discretion', which can hollow out the obligation entirely. Second, where the parties genuinely cannot fix the steps in advance, consider a mechanism — an independent expert determination on whether reasonable steps were taken — rather than an unenforceable agreement to agree.

A note for both sides

For the party giving the promise, the discipline is to promise only what it is prepared to fund and prioritise, and then to record the effort as it happens. For the beneficiary, the discipline is to negotiate visibility at the outset — reporting obligations, named contacts, periodic reviews — rather than discovering two years later that no one can say what was done.

The adjective matters, but it is a blunt instrument. Clarity about steps, cost and consequences will always tell the parties more about who bears the risk than the choice between 'reasonable' and 'best'. Where a contract turns on a phrase of this kind, early advice on the drafting — or on the evidence available when a dispute is brewing — is usually far cheaper than the argument itself.