How to price variations, and get them paid

Price a variation the same way you priced the original job: labour at your day rate, materials at cost plus your usual markup, and any knock-on costs such as extra scaffold hire or a longer programme. Then get the price agreed in writing before you start. If no price is agreed with a householder, the law only lets you charge a reasonable one.

What counts as a variation?

A variation is any change to the work the client agreed to pay for. JCT's guidance for its Minor Works contract describes it as a change to the work that can be an addition, an omission, or a change to the order or period of the work. That definition is useful on any job, with or without a JCT contract.

Most variations on domestic work come from three places: the client changes their mind ("can we move the bifold?"), something unexpected turns up (rotten joists under the old floor), or the original quote left something out. The first two are variations. The third is your problem unless your quote listed it as an exclusion or assumption, which is why clear exclusions on the quote save so many arguments later.

How do you price a variation?

Use the rates you already have. If your day rate covers labour, overheads and profit, and you mark materials up by a set percentage, a variation is the same sum on a smaller scale.

1. Describe the change in one sentence.

   "Supply and fit one 1000 × 1000 mm flat rooflight in the extension roof, including kerb, upstands and making good inside." If you can't describe it, you can't price it.

2. Count the labour in days or half-days.

   Include the trades it touches. A rooflight is joinery, roofing, plastering and sometimes an electrician.

3. Price materials at your cost plus your usual markup.

   Use a current merchant price, not last year's. See how much to mark up materials.

4. Add knock-on costs.

   Extra scaffold or plant hire weeks, a second skip, extra days on the programme, protection, cleaning.

5. Note what it does to the finish date.

   If the variation adds two days, say so in writing. It protects you if the client later complains the job ran late.

6. Send it, get a yes, then start.

   A price agreed after the work is done is a negotiation you've already lost.

The day rate comes from working out your overheads per man-day. If you price variations at labour cost alone, every change the client asks for makes the job less profitable.

How do you price an omission?

When the client takes something out, credit them for what you no longer have to do, less anything you have already spent or can't cancel. Credit the price you quoted for that item, not a guess.

Say the original quote included £1,450 for a utility room tiled floor, and the client now wants to fit their own flooring later. You had already bought £310 of adhesive and tiles that the merchant won't take back. The credit is £1,450 less £310 = £1,140, and the client can keep the materials. Put it in writing with the same template as an addition.

Don't let omissions and additions cancel out in a conversation. "We'll call it even" leaves no record. List each variation separately, with its own price or credit, so the final account adds up.

Do you need written agreement for a variation?

Yes, in practice. For work for a householder, the Consumer Rights Act 2015 treats what you tell a consumer about the service as part of the contract if they rely on it. Where the contract doesn't set a price for the work, the consumer has to pay a reasonable price and no more, and what counts as reasonable is a question of fact. A written price agreed before the work removes that argument.

Written doesn't mean a formal document. A WhatsApp message with the description, price and effect on the finish date, and a reply saying "yes, go ahead", is a clear record. Keep it with the job.

On commercial work, the main contract usually says who can instruct a variation and how it is valued. Under JCT Minor Works, for example, only the architect or contract administrator can issue instructions, so a change asked for by the client's site manager is not an instruction until it comes through the right person. If you're a subcontractor, get the instruction in writing from whoever the subcontract names before you do the work. Payment notices and pay less notices then decide when you get paid for it; our guide to payment and pay less notices covers the deadlines. Note that the Construction Act payment rules don't apply to a contract with a residential occupier for work on their own home.

Hi client name,

As discussed on site today, here's the price for the change to job address.

Variation number: one-sentence description of the change

Price: £amount + VAT = £total
Effect on the programme: adds number working days. New expected finish: date.

This is in addition to the original quote quote number. We'll add it to the next stage invoice.

If you're happy to go ahead, reply "yes, go ahead" and we'll start it on date. We won't start the extra work until we hear from you.

Thanks,
your name
business name

How do you make sure variations get paid?

Bill each variation with the next stage payment, as its own line. Variations left to the final invoice turn into one large, disputed number at the moment the client has the least reason to pay quickly.

That builder agreed changes on site and meant to write them up in the evening. Often he didn't, so the extras went unbilled or were argued over at the end. What worked was recording each change the moment it was agreed, as a voice note, and turning that into a priced variation the same day. Our guide to recording variations by voice note covers that habit in detail.

What if the client disputes a variation price?

Go back to your written record and your rates. If you sent the description and the price and got a "yes" before starting, the conversation is short. If you didn't, offer a breakdown on the same basis as the example above: days, rate, materials at cost plus markup. A price built from your normal rates is easier to defend as reasonable than a round number. If the amount is large and the client still won't pay, get advice from a solicitor before it turns into a dispute about the whole job.

Common questions