Clause 10: Mutual Trust and Co-operation

NEC clause 10.1 is the opening duty in the contract. In NEC3 ECC, it requires the Employer, Contractor, Project Manager and Supervisor to act as the contract says, with mutual trust and co-operation. NEC4 splits that in two: 10.1 is about acting as stated, and 10.2 is about the spirit of mutual trust and co-operation.

The clause is short, but people cite it for a lot, often wrongly. This page explains what it does in everyday contract management, without legal case references. If a real dispute turns on it, take legal advice. It's part of the NEC definitions glossary and the guide to the core clauses.

What each half does

Part	Plain meaning	Practical effect
Act as stated	Do what the contract says the role does	NEC writes most clauses in the present tense ("the Contractor submits"). This is what turns those descriptions into obligations
Mutual trust and co-operation	Behave openly and help the other side do its job	Shapes how you handle the things the contract leaves to judgement

The first half isn't a formality. It covers the Project Manager and Supervisor too, so a Project Manager who doesn't reply, doesn't assess or decides without using the procedure falls short of what the clause asks, as well as triggering any specific remedy.

What it looks like in practice

Situation	Behaviour that fits	Behaviour that doesn't
Contractor spots an error in the Client's drawings	Raises it straight away	Prices on the error, then waits to claim
Project Manager thinks a quotation is missing a section	Says what's missing, with reasons	Rejects it with a one-line reply
Contractor knows of a compensation event	Notifies it promptly, and the Project Manager replies on the merits	Holds the notice back until the last possible day to spring a surprise
Project Manager knows the Client's supply will be late	Gives an early warning	Stays silent, hoping the Contractor runs late too

What it can't do

Teams sometimes reach for the clause as if it were a general override. Be careful with that.

• It doesn't obviously lift time limits. If a Contractor misses the 61.3 period, an appeal to trust is a weak answer, because the specific clause sets out what happens.
• It doesn't rewrite the bargain. The Client isn't made to pay more because a job has gone badly for the Contractor. Clause 12.3 still governs changes to the contract.
• It doesn't require agreement. People can act in that spirit and still disagree firmly. Rejecting a quotation for a good reason isn't a breach of trust.
• It doesn't stop you enforcing. Applying a contract term, even an unwelcome one, is acting as stated.

A worked example

A fictional culvert job. The Contractor's quotation is due, and it needs information only the Client's utility consultant has. It asks twice, and gets nothing. Instead of quoting blind, it writes to the Project Manager explaining what's missing. Under 62.5, they agree before the quotation is due to extend the time.

Both have behaved well. The extension gives them time. But note where that power comes from: clause 62.5, not clause 10. The spirit explains why they agreed. The other clauses supply the mechanics. That's the usual way these work together.

How to use it

1. Start with the specific clause. If a particular provision covers your situation, use it first.
2. Use it to set the tone. Kick-off meetings are a good time to agree what it means for your team, such as reply standards and how to raise problems.
3. Use it sparingly in letters. A letter that quotes 10.1 for every disagreement soon sounds empty.
4. Cite the right number. In NEC4 ECC the trust wording is at 10.2. Some older templates quote 10.1 for it, which is correct only for NEC3.

For the wider behaviours, see the guide to collaboration on NEC contracts.

Related guides

• NEC Definitions: A Glossary of Key Terms
• Clause 13: Communications
• Clause 14: Project Manager and Supervisor
• Clause 11: Identified and Defined Terms
• Working Areas
• Works Information

This guide is general information in our own words, not legal advice. Your contract and its Contract Data always govern. NEC, NEC3 and NEC4 are trade marks of Thomas Telford Ltd; Contract Status is not affiliated with or endorsed by NEC.