Two very different promises
An obligation of means is a promise to perform with competence - to apply reasonable skill and care towards an objective. If the objective is not reached despite proper effort, there is no breach: the party did what it promised. An obligation of result is a promise to achieve the outcome itself. If the outcome is not delivered, it does not matter how hard or how well the party worked.
"The consultant will use reasonable skill and care to improve the client's systems" is the first kind. "The consultant will deliver a system processing 10,000 transactions per hour by 31 December" is the second. The words look similar; the risk they carry could not be more different.
Why the risk allocation is opposite
Under an obligation of means, the risk of a bad outcome sits with the client: the supplier can perform the contract perfectly and still deliver something that does not solve the client's problem. Under an obligation of result, the risk sits with the supplier: it can work brilliantly and still be in breach because an external factor stopped the result being achieved.
Neither is right or wrong - they are different deals. What goes wrong is signing up to one while believing you agreed the other.
Where it sits in English law
English law does not always force the choice; it reads the words. Some obligations carry an implied standard of reasonable care and skill, particularly the supply of services, while others are strict - an obligation to deliver goods or works that meet a specified description, or that are fit for a stated purpose, is judged on the outcome rather than the effort.
Because the default is not uniform, the safe course is to state the standard expressly for each significant obligation rather than leave a court to infer it.
How scope disputes grow from this
The classic pattern is a supplier that believes it promised effort and a client that believes it bought an outcome, on wording vague enough to support both. That is, in substance, what divided the parties in the TCS v DBS dispute: how far one side had promised a working result rather than just its part of the work. When the contract does not resolve it, litigation does - expensively.
The lesson is to make the standard explicit before the relationship is under strain, not after.
How to draft the standard
For an effort obligation, say so: "shall provide the Services using reasonable skill and care", and avoid outcome language that implies a guarantee. For a result obligation, specify the result and the test: the deliverable, the measurable standard it must meet, and the date. Where an outcome genuinely matters, do not settle for an endeavours promise - name the result.
In review, the highest-value catch is a redline that quietly converts a result into an effort obligation, or back, because it moves the risk of failure from one party to the other without touching the price.
Use at the desk
Practical checklist
- For each significant obligation, decide and state whether it is effort (reasonable skill and care) or result (a specified outcome).
- Use "reasonable skill and care" wording for effort obligations, and avoid outcome language that implies a guarantee.
- For result obligations, specify the deliverable, the measurable standard, and the date.
- Do not leave the standard to be implied - the default is not uniform across obligations.
- Where an outcome matters, name the result rather than settle for an endeavours promise.
- In review, flag redlines that convert a result obligation into an effort one, or vice versa - they move the risk of failure.
This guide is informational only and is not legal advice. It does not replace advice from licensed counsel on the facts of a specific transaction.
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