Public contracts rarely stand still. A customer adds users, moves a deadline forward, swaps a discontinued product, or responds to a new regulation. For a small or medium sized supplier, the way these changes are handled can decide whether a contract remains profitable or quietly turns into unpaid work. That is where change control comes in.
Change control is the agreed process for requesting, assessing, approving and recording changes to a contract after it has been awarded. It is both an administrative routine and a commercial protection. You can read the short definition in our change control glossary entry, but this article goes further and shows how it works in practice for SME bidders.
This guide reflects the UK position as at October 2026. Under the Procurement Act 2023, contract changes are generally called modifications. A contracting authority may modify a public contract only where the change is permitted by the Act, is not substantial, or qualifies as a below-threshold modification. Understanding those limits helps you avoid agreeing to something the authority is not legally allowed to do.
Why change control matters to bidders
If you win public work, you will almost certainly be asked to change something during delivery. Common requests include:
- Additional users, sites or service hours
- A revised delivery timetable
- New reporting or security requirements
- A replacement product or technology after a line is discontinued
- Changes caused by legislation, supply-chain disruption or operational need
- A reduction or expansion in volume
Without a clear process, an SME can drift into trouble. You might deliver work with no firm price or payment commitment, accept obligations you cannot resource, breach service levels after an informal change, or lose the evidence you need to recover additional costs. Worse still, you could agree a change that the authority is not legally entitled to make, which creates risk for both parties.
Treat the change-control clause as commercial armour, not paperwork. It defines who can ask for a change, what the request must contain, how the impact is assessed, and when the change becomes binding. Before you even submit a bid, decide how much flexibility your price genuinely includes, because evaluators and contract managers will expect you to honour whatever you signed up to. A sensible bidder prices the base requirement tightly and keeps a clear mechanism for charging extra work fairly. If you are weighing whether a contract is worth pursuing at all, the discipline you apply to change control should feed into your go or no go decision, because a weak change clause on a volatile contract can wipe out your margin.
The basic change-control process
A practical change-control process usually moves through a predictable sequence. Following it keeps you in control and gives you an evidence trail if a dispute arises later. The core stages are:
- Identify the requested change and who has asked for it
- Describe the reason and the intended outcome
- Assess the effect on scope, price, timetable, resources and risk
- Check the contract's change mechanism and permitted routes
- Obtain written approval from authorised representatives on both sides
- Update the relevant contract documents and records
- Implement, monitor and formally close the change
The single most important discipline is this: do not start chargeable additional work merely because someone made a request in a meeting or sent an informal email. Ask for a written change request and confirm whether the customer wants an estimate, a full proposal, or immediate action under an emergency provision. A quick acknowledgement that says "thank you, we will assess this through the change-control procedure and respond with an impact assessment by Friday" buys you time and protects your position.
Keep every change note numbered and dated, and record the authorised signatory who approved it. Good contract managers on the buyer side will expect the same rigour from you, and strong records make renewals and future bids easier. Your contract manager or delivery lead should own the log so that nothing slips through informally. This habit also feeds your win-loss learning, because a well-documented change history shows exactly where scope crept and where your pricing assumptions held.
What to look for in the tender documents
Much of your change-control risk is set before you win anything, in the contract terms attached to the tender. Read them closely rather than assuming they are standard. Find and review:
- The change-control clause and the variation or modification form
- The authority's authorised signatories for approving changes
- Pricing rules for additional work, including any rate card
- Indexation provisions and how prices move over the contract term
- Volume-flexing provisions that may allow quantities to rise or fall
- Service-credit and performance-reporting rules
- Requirements for subcontractor approval
- Change-related notice periods
- Any stated assumptions, dependencies or known risks
Record each of these in a bid-risk register so that you price them deliberately. If the process is unclear, raise a clarification question before the deadline rather than guessing. A useful clarification might ask the authority to confirm whether additional service volumes will be instructed through the change-control procedure, how pricing will be calculated, and whether the authority will give minimum notice before implementation.
Pay particular attention to wording that lets the customer change scope unilaterally without a matching adjustment to price, timetable or risk. That is a one-sided term and you should flag it. It is also worth understanding how the wider contract framework operates, because change control interacts with call-off arrangements. If you are bidding through a framework, our guide to call-off contracts for SME bidders explains how variation rules can differ between the framework and the individual call-off.
Worked examples you can learn from
Theory is easier to apply once you see it in action. Here are four short worked examples drawn from situations SMEs meet regularly. In each case the lesson is the same: assess the impact, propose terms, and get written approval before you commit.
Extra service users
An SME provides a helpdesk for 500 users at £40,000 per year. Six months in, the authority asks it to support 100 more. The supplier should calculate the additional licences, support hours, recruitment or overtime, training and any effect on service levels and data protection. Suppose the extra cost is £8,000. The change proposal should state the additional 100 users, the revised annual price of £48,000, the implementation date, the assumptions, and the approval required. Do not simply start supporting the extra users at the old price unless the contract clearly says the original price includes that headroom.
A timetable change
A construction SME is due to finish by 30 June, and the authority asks for 31 May. Acceleration may need extra labour, overtime, expedited materials and more supervision. The supplier should produce an acceleration assessment rather than nodding along. A worked total might be additional labour £12,000, overtime premium £4,500, expedited materials £2,000 and extra supervision £1,500, giving £20,000. The change note should confirm whether the new date replaces the old one and whether delay damages or service credits are recalculated.
Replacing a product and a new legal requirement
Two more quick cases round this out:
- A specified hardware model is discontinued and the manufacturer offers an equivalent. Compare specification, compatibility, cyber-security, warranty, support period, price and delivery, then obtain written approval and retain the discontinuation evidence. Never substitute on the strength of a phone call.
- A cleaning contractor is asked to add reporting after a regulatory change. Distinguish between work already required by law and included in the price, and genuinely new customer-specific administration. If the contract says you must comply with changes in law at your own cost, extra payment may only be available where the request goes beyond that obligation.
Procurement-law limits on changes
The authority cannot simply agree any change you both like. Under the Procurement Act 2023 it must normally justify a modification using a permitted route. Warning signs you should recognise include:
- A substantial modification that materially changes the scope or shifts the economic balance in the supplier's favour
- A change that extends the term by more than ten per cent of the maximum term stated at award
- A below-threshold modification where the value moves by more than ten per cent for goods or services, or fifteen per cent for works
- A change that would require a contract change notice to be published but has not been
You do not have to make the legal determination for the authority, but you should ask who has approved the change and on what basis. If a modification requires a notice and the contract value, including the modification, exceeds the relevant threshold, the authority may have to publish the modification details, and it may also observe a voluntary standstill period before proceeding.
This matters because demand for public work is heavy in some regions, and SMEs that handle changes professionally win repeat business. KimonBids live data for October 2026 shows 1,186 tenders published in London in the last 30 days, by advertised region, and 713 tenders published in the South East. Those figures underline how much work flows through public buyers, and why a reputation for clean, well-documented change control helps you compete for the next contract as much as the current one. If you want to broaden where you bid, our guide to expanding beyond your home region shows how to apply the same discipline across more markets.
Frequently asked questions
What is the difference between change control and a modification?
Change control is the practical process you follow to request, assess, approve and record a change during delivery. A modification is the legal term the Procurement Act 2023 uses for a change to a public contract. In short, you run change control to deliver a modification that the authority is permitted to make.
Can I start extra work before the change is approved?
As a rule, no. Starting chargeable work on the back of an informal email or a verbal request leaves you exposed if payment is later disputed. Ask for a written change request, submit an impact assessment, and only begin once an authorised representative has approved it in writing, unless the contract has a genuine emergency provision.
How much can a public contract change under the Procurement Act 2023?
A modification must use a permitted route. A below-threshold modification generally must not move the value by more than ten per cent for goods or services, or fifteen per cent for works, and must not materially change the scope. Larger or substantial changes need a different permitted ground and may require a contract change notice.
What should a change note actually contain?
A good change note records the change requested, the reason, the revised price, the implementation date, any assumptions, the effect on the timetable and service levels, and the signatures of authorised representatives on both sides. Number and date it, and keep it with your contract records.
What if the authority wants a change but refuses to adjust the price?
Set out your impact assessment clearly and state what you can and cannot commit to on the existing commercial assumptions. If the contract allocates that cost to you, for example a change-in-law clause, additional payment may not be due. If it does not, you are entitled to propose a fair price adjustment before agreeing.
