How to dispute a payment application rejection under NEC4

You submitted your assessment for payment. Valued the work honestly. Included implemented CEs. Applied the correct retention percentage. Then the PM's payment certificate comes back significantly lower. No detailed explanation. Maybe a one-liner about "not agreeing with the valuation."

This happens on almost every NEC4 project I've worked on. Most M&E subs don't know their options. You do have options. The contract gives you a clear process. But the window to act is narrow. Miss the deadlines, lose your rights.

Understanding why your AFP was rejected

First, terminology. Under NEC4, you submit an application for payment (AFP). The PM assesses the amount due and issues a payment certificate. That certificate is the PM's assessment. It may or may not match yours.

Common reasons the PM certifies less than you claimed:

• Disagreement on measured quantities: You say 70% of the pipework is done. The PM says 55%. That's a valuation dispute.
• CEs not included: You included implemented CEs. The PM excluded them, claiming they weren't properly implemented or disputing your quotation.
• Retention applied differently: You calculated retention one way. The PM applied a different percentage or applied it to items you believe are retention-free.
• Disputed variations: You included work you consider a Scope change. The PM considers it within the original scope and already covered by the contract price.
• Defects deduction: The PM deducted for alleged defects you either dispute or weren't aware of.

Before you do anything else, understand specifically why the number is different. If the PM hasn't provided a breakdown, ask for one. Not a polite email. A formal communication under the contract asking the PM to explain the basis of their assessment.

The PM's obligation to certify or explain

Under NEC4 clause 50, the PM assesses the amount due at each assessment date. The certificate must show the PM's assessment of Price for Work Done to Date (PWDD), plus other amounts due, minus deductions. This isn't discretionary. The PM must carry out this assessment properly and certify the correct amount.

Under the Construction Act, every construction contract must provide payment notices specifying the amount due and the calculation basis. If the PM's certificate doesn't explain the assessment, it may not be a valid payment notice. The payment notice provisions are mandatory. The parties can't contract out of them.

If you receive a certificate with no breakdown, write formally to the PM and the Contractor. Note the certificate doesn't comply with payment notice requirements. Request a detailed breakdown within a stated period. Keep a copy. This correspondence matters if you adjudicate later.

Formal dispute process under NEC4 Option W

NEC4 provides dispute resolution through Option W1 or W2. Most UK NEC4 subcontracts use Option W2 because the Construction Act applies.

Under Option W2:

1. Notification of dissatisfaction: Notify the PM you're dissatisfied with their assessment. You must do this within 4 weeks of the PM's action. Don't delay. Miss this window and you may lose the right to refer the dispute.
2. Discussion period: Typically 2 to 4 weeks for the parties to try resolving through discussion. Use this time, but don't rely on it. Start preparing your evidence file in parallel.
3. Referral to adjudication: If discussion fails, refer to adjudication. Under the Construction Act you can refer any dispute to adjudication at any time. The NEC4 process can't take that right away.

The deadlines are critical. I've seen M&E subs lose legitimate claims worth tens of thousands because they missed the notification window by a few days. Adjudicators enforce time bars strictly. Put the deadlines in your diary the moment you receive a certificate you disagree with.

Building your evidence file

If you're heading towards adjudication, the evidence file is everything. The adjudicator decides based on the documents in front of them. They weren't on site. They didn't see the work. They rely entirely on what you can prove on paper.

For a payment dispute, your evidence file should include:

• Your application for payment: The full AFP with all supporting documents, breakdowns, and valuations as submitted.
• The PM's payment certificate: With whatever breakdown was provided, or a note that no explanation was given.
• Your correspondence: Every letter, email, or formal communication about the disputed amount. Chronological order.
• Measured work evidence: Progress photos with dates, inspection records, sign-off sheets, joint measurements. If you're disputing a measured quantity, show the adjudicator what was actually installed.
• CE documentation: For each disputed CE: notification, PM's response (or lack of it), your quotation, revised quotations, implementation record. The adjudicator follows the CE process step by step. If you followed the procedure, you're in a strong position.
• Programme records: The Accepted Programme at the time of the dispute, showing planned vs actual. If delay is a factor, the programme is essential.
• Contract documents: Subcontract, Scope, activity schedule or BoQ, Z-clauses and amendments. The adjudicator needs the contract to make a decision.

When to involve an adjudicator

Adjudication isn't free. A typical adjudicator charges between 250 and 400 pounds per hour. A payment dispute can involve 30 to 60 hours of adjudicator time. Add your legal or claims consultant costs. You're looking at 15,000 to 40,000 pounds total for a contested adjudication.

That means it only makes commercial sense if the disputed amount justifies the cost and your evidence is strong. As a rough guide, I wouldn't adjudicate a payment dispute under 50,000 pounds unless the principle matters for future applications on the same contract.

Before you pull the trigger, get an honest assessment from someone independent. Not your PM who's been living the dispute. Someone fresh who can look at the documents objectively. If your CE notifications were late, your programme wasn't accepted, or your quantities can't be verified, those are weaknesses the other side will use.

There are tactical points too. Adjudication produces a temporarily binding decision. Either party can have it finally determined by tribunal (usually arbitration or court) afterwards. If you win, the other side must pay, but they can challenge later. In practice, most decisions stick because re-running the dispute is prohibitively expensive. But winning at adjudication isn't always the end.

The time to prepare for a payment dispute is not when it happens. It's every day, on every project, from day one. If your daily reports are thorough, your CE notifications timely, your programme up to date, and your applications properly detailed, disputing a wrongful rejection becomes straightforward. You just compile records you've already been keeping. If you haven't been keeping those records, you're starting from weakness. No amount of legal argument compensates for missing evidence.