The Public Sector Contract Transparency Mandate.

Navigating Contract Changes under the Procurement Act 2023

If you’re working in the UK infrastructure market, you’ve likely spent the last few months getting to grips with the biggest shake-up in procurement for a generation. Since the Procurement Act 2023 (PA23) went live on 24 February 2025, the old EU-derived rules have been swapped for a regime that places a massive premium on transparency (Beale & Co, 2025; PBC Today, 2025).

For anyone managing asset enhancement or replacement contracts, the most visible change isn't in how we award tenders, but in how we handle what happens after the ink is dry. Specifically, we’re talking about the "Contract Change Notice" (CCN), the mechanism that ensures contract modifications aren't just an internal conversation, but a matter of public record.

The "Golden Thread" of Visibility

The philosophy here is simple: transparency is the "golden thread" that should run through the entire lifecycle of a project (AtkinsRéalis, 2021; Crown Commercial Service, 2021). Under Section 75 of the Act, the general rule is that you must publish a CCN (coded as notice type UK10) on the Central Digital Platform before you can legally modify an active public contract (Find a Tender, 2025a; UK Government, 2023).

But let's be honest: in construction, things change. Ground conditions surprise us, or an "asset enhancement" suddenly becomes a lot more complex than originally planned. So, when exactly does a project tweak cross the line into a mandatory public disclosure?

The Quantitative Triggers: The 15% Rule

For works contracts, the bread and butter of the infrastructure sector, the Act provides a "de minimis" safe harbour. You generally don't need to publish a CCN if the change is "below-threshold" (Cabinet Office, 2025a; Fieldfisher, 2024). This means:

•  Value: Total cumulative modification increases or decreases the contract value by 15% or less (Browne Jacobson, 2024).

•  Duration: The total cumulative term changes by 10% or less of the original maximum term (Fieldfisher, 2024).

However, keep an eye on the "aggregation" trap. These thresholds aren't for each individual change; they are cumulative. If you make three 6% changes to a bridge enhancement project, the third one pushes you over the 15% limit, and you’ll need to hit the "publish" button on a CCN (Cabinet Office, 2025a; Procurement Portal, 2024).

It’s Not Just About the Money

Even if the value change is small, you might still be forced into the public eye if the modification is "substantial." Under Section 74(3), a modification is substantial if it "materially changes the scope" (UK Government, 2023). In infrastructure terms, this means providing works of a kind not already in the contract (Fieldfisher, 2024).

If you’re replacing a stretch of railway and decide to add a completely new signalling sub-station that wasn't in the original tender, that’s likely a change in scope. Even if you’ve stayed under the 15% value cap, you’ll need a CCN to justify the change under a Schedule 8 "permitted modification" ground, like "unforeseeable circumstances" or "additional works" (Brabners, 2024; Fieldfisher, 2024).

Major Projects: The £5 Million Threshold

For the big-ticket items, those major asset replacements exceeding £5 million, the transparency requirements step up a gear. If a modification triggers a CCN and the contract is worth more than £5 million (including that modification), the authority must also publish a copy of the actual modified contract or the modification document itself within 90 days (Cabinet Office, 2025c; Find a Tender, 2025a).

This turns your project history into a searchable digital record. Competitors can see not just that you changed the contract, but exactly what terms were updated (Cabinet Office, 2025d; Welsh Government, 2025b).

The Utility Paradox

For those in the private utilities sector (water, energy, etc.), there’s a bit of a silver lining. While you still have to publish CCNs for major changes, you are exempt from the requirement to publish the actual contract documents for modifications over £5 million (Welsh Government, 2025a; Find a Tender, 2025a). You also aren't bound by the 50% value cap that limits standard public authorities when they're dealing with "unforeseen" modifications (Brabners, 2024; Fieldfisher, 2024).

Managing the Risk: The Voluntary Standstill

Perhaps the most important tactical decision for a contracting authority is whether to observe a voluntary 8-working-day standstill after publishing a CCN (Cabinet Office, 2025b; UK Government, 2023).

Why wait? Because it buys you legal certainty. If a competitor is going to challenge your modification as being "unlawful" or "substantial," they have to move fast. If you ignore the standstill and start the works, you risk a court "setting aside" the modification later, which is a nightmare scenario mid-build (Taylor Wessing, 2025; Browne Jacobson, 2024).

The Bottom Line

In the post-PA23 world, the days of "quiet variations" are over. Whether you’re dealing with crumbling RAAC concrete or a high-tech asset enhancement, the system is designed to track every penny of "value creep" .

The successful projects won't just be the ones delivered on time and budget; they'll be the ones where the modification strategy was planned with total transparency in mind from day one.

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