The Most Common NEC Mistakes

The most common NEC mistakes are procedural, not legal: notifying late, letting the programme go stale, replying late, quoting poorly and keeping weak records. Nearly all of them can be fixed by a simple routine, and they usually cost more than any question of contract interpretation.

The list below is drawn from how the NEC4 Engineering and Construction Contract (ECC) works, with notes for NEC3. It is ordered roughly by how much damage each one does. Dedicated pages go deeper on compensation event mistakes, early warning mistakes and payment mistakes. It's all part of managing NEC contracts.

Contractor-side mistakes

Mistake	What it costs	The fix
Notifying a compensation event after eight weeks	The Prices and dates may not change (61.3)	Tell site teams to report oddities the same day. Check diaries weekly
Not warning	The event is assessed as if you had warned (61.5, 63.7)	Warn first, and refine it later
Letting no programme be accepted	A 25% holdback from the Price for Work Done to Date where none was identified (50.5); weaker delay evidence	Submit a complete programme on time, using a checklist
Not chasing a late reply	Treated acceptance needs your second notification	Diarise and send it
Quotations without working	Project Manager's own assessment (64.1)	Follow a clear build-up
Poor cost records on Options C, D and E	Disallowed Cost	Set up the records before work starts

Project Manager and Client mistakes

Mistake	What it costs	The fix
Replying late, or not at all	60.1(6), or treated acceptance of a quotation you never reviewed	A shared reply date list, and a deputy
Instructing without notifying the event	The event stays open with no bar on notification (61.3 exception)	Notify at the same time as the instruction (61.1)
Rejecting a programme for a reason the contract doesn't give	A possible event under 60.1(9); no Accepted Programme	Use only the 31.3 reasons, with specific details
Assessing to a budget	A weak assessment that can be overturned	Assess on the facts, with visible working (64)
Letting the Client instruct directly	Confusion over authority and cost	A single channel, agreed at kick-off
Vague Scope at tender	Many later instructions, and arguments over what was included	Invest in the Scope before going to market
Late Client-provided items	60.1(3), often with knock-on delay	Keep a list of them, shown on the programme

Mistakes both sides make

1. Keeping separate registers. Two lists diverge, and the argument becomes about the list. Use one numbering system and reconcile monthly.
2. Treating a warning as a claim. An early warning is a risk tool. If people fear that raising one means admitting fault, or making a claim, they stop raising them, and the whole mechanism fails.
3. Agreeing things in meetings only. A communication has to be in a form that can be recorded (13.1). Minutes don't replace notices.
4. Mixing up periods across contracts. The subcontract uses different figures. Other forms do too. See the table of time periods.
5. Leaving compensation events until the end. NEC's method relies on forecasting close to the event. A backlog at Completion means reconstructing history, which is just what the contract is built to avoid.
6. Ignoring the Z clauses. A contract with heavy amendments isn't standard NEC. Read yours, and make sure your templates reflect them.
7. Using the wrong edition's language. NEC3 ECC has the Employer, Works Information and the Risk Register. NEC4 has the Client, Scope and the Early Warning Register. Using the wrong clause number on a notice invites a technical objection.
8. Treating acceptance as approval. Under 14.1, it doesn't change the Contractor's responsibility, and a Project Manager's acceptance won't turn a poor design into someone else's problem.

A worked example of several at once

A fictional footbridge job, which goes wrong in small steps. The Contractor doesn't warn of a late steel delivery from a Client-nominated source. The Project Manager, on leave, doesn't reply to a programme. The team then agrees a re-sequence verbally in a meeting. Four months later, the Contractor notifies a compensation event for the delivery. The Project Manager replies that it is out of time, and there's no Accepted Programme to measure against, since the last one was never replied to. Neither side's position is clean.

Any one of these would have been fine on its own. A warning, a chased reply or a written instruction would each have broken the chain. A short weekly routine catches them before they become a tangle.

A five-minute self-check

• Do we know every reply due in the next two weeks?
• Is the latest programme accepted, and how old is it?
• How many compensation events are over eight weeks old and unimplemented?
• Do both sides have the same register?
• Have we had a warning raised recently? If not, why not?

Related guides

• Managing NEC Contracts: A Practical Guide
• NEC on Building Projects
• NEC on Maintenance and Term Contracts

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.