How to Handle Change Orders in Construction (Keep Your Margin When Scope Changes)

Change orders in construction are where the money goes if you are not paying attention. You quoted the job clean, priced it at a good margin, then the client asked for extras. You did the work. The invoice came in higher than the original quote. Now they are disputing the extra cost - and you have nothing in writing.

This is a conversation about how to handle change orders in construction without losing the margin. And it sits at the heart of construction arbitrage - the model where you hold the contract, coordinate the subbies, and protect the spread in between. A general contractor (main contractor in the UK) who does not control scope changes does not control the margin. That is the whole game.

What a change order actually is

A change order is a written amendment to your construction contract. It documents any change to the original scope, cost, or schedule - whether the client asked for extra work, you found something unforeseen on site, or part of the original spec was cut.

The key word is written. A client saying yes over a phone call is not a change order. An email saying go ahead is borderline. A signed document that states the change, the cost, and any change to the timeline - that is a change order. That is the one that holds up.

Why most contractors lose money on scope changes

Take a bathroom remodel quoted at $28,000 (figures in USD - the model and the math are identical in any currency). The margin was $5,600 - 20 percent. During the job the client asks you to tile the hallway, replace the vanity with a custom unit, and reroute a waste pipe you found was misaligned.

Each of those is a legitimate extra. But if you did them on a verbal agreement and the client disputes any part of it, you are now chasing $4,200 in additional costs with nothing in writing. That is most of your margin on the original job, gone. You just worked three weeks for nothing.

This is not rare. A 2025 industry survey of construction professionals found that 56 percent named scope creep and change orders as the primary cause of costly project rework - ahead of unforeseen site conditions and design errors. The money is in the change orders. That means the change order process is one of the most important things in your business.

The right way to document a change order

Keep it simple. A change order document needs five things:

• A description of the change - what is being added, removed, or adjusted
• The reason for the change (client request, unforeseen condition, design revision)
• The adjusted cost, broken down if the client needs it
• Any change to the completion date
• Signature lines for you and the client, with a date

One page is enough. Both parties should be able to read it in two minutes and know exactly what was agreed. The longer it is, the longer it sits unsigned.

How to price a change order

Price it the same way you priced the original job. Materials, direct labour, your overhead allocation, and your margin. Do not discount. Change orders are often your highest-margin work because the client has already committed to the relationship and the job is already mobilised.

Some operators add a flat change-order administration fee - typically 5 to 10 percent of the direct cost on top of margin - to cover the disruption to procurement and scheduling. On a small change on a large job, you might waive it. On a significant scope addition that reshuffles your whole programme, it is fair to charge it.

If you are buying in subcontractor quotes for the extra scope, use the same approach as pricing the original job - get your sub's rate, add your overhead and margin on top, and present the total to the client without breaking down the subcontractor cost.

How to get the client to sign before work starts

This is where most contractors lose it. They get verbal approval, do the work, invoice - and the client either disputes the amount or claims they did not agree to all of it.

The rule is simple: no signed change order, no extra work. The way to make this stick is to frame the change order as protection for both of you - not as paperwork you are forcing on them.

Say this: 'I am going to write up what we discussed so we are both clear on exactly what is included and what it costs. Once you have signed that off I can get it scheduled.' That is not bureaucracy. That is how professionals run jobs. Clients who understand construction will not resist it.

What to say when the client pushes back

Some clients resist. They say it is only a small job, they trust you, there is no time. Here is how to handle it:

What happens if you do the work without a signed change order

You carry the risk. If the client disputes the extra cost, you are arguing from memory against a client who may have a very different recollection of what was agreed. In most jurisdictions, verbal agreements in construction are difficult to enforce above a threshold - and even where they are theoretically enforceable, proving them costs more than the change order was worth.

There is also a second problem. Doing unapproved extra work - even with good intentions - can give the client leverage on the original contract. They can use the unauthorised work as grounds to dispute the final invoice.

Build the change order process into the original contract

The cleanest fix is a change order clause in the original contract. One sentence covers it: "Any changes to the agreed scope of work require a written and signed change order before work on the change begins." When the client signs the contract, they are agreeing to the process too. That removes almost all the friction when a change comes up on site. See how to write a construction contract for what else that document needs.

This is not about being difficult. It is about having a clean record of what was agreed at every stage of the job. It protects you. It also protects the client - they know what they are paying for and there are no surprises on the final invoice.

The operator who owns the contract owns the scope. The one who does not have it in writing owns the argument.

Change orders and the arbitrage margin

When you are running the construction arbitrage model - winning the contract, coordinating subbies, keeping the margin - change orders are a significant opportunity as well as a risk. A client who is happy with the work will ask for more of it. Every extra they request is a clean margin opportunity if you handle it with a proper process.

The contractors who lose on change orders are the ones who do the work first and argue about money second. If you want to understand how protecting the margin on extras connects to cash flow and payment terms across a construction business, listen to THE EDGE. It is a listening book and free to start.

Bottom line

Change orders in construction are not optional paperwork. They are what stands between your quoted margin and a weeks-long dispute about who agreed to what. Document every change. Price it properly - the same way you priced the original job. Get it signed before the work starts. Build the process into the original contract so it is expected, not resisted. One unsigned extra is enough to wipe the margin on an entire job.