CMA Written Estimates for Vets: The £500 Rule Explained

When you will have to give a written estimate

Order made; this duty applies from 2027. The CMA made the Veterinary Services Market Investigation Order 2026 on 22 September 2026, and it came into force the next day. Under Article 3 of the Order, written estimates have a compliance date of 22 June 2027 for larger businesses (15 or more first-opinion practices and/or out-of-hours centres) and 22 September 2027 for smaller ones, and practices must comply from the next working day after that date.

Under Article 11 of the CMA Order, your practice will have to give a pet owner a written estimate when the treatment pathway a vet recommends is reasonably likely to cost £500 or more, including VAT, and more than 20% of that £500 threshold (so more than £100) relates to costs still to come. If the likely total then rises by 20% or £500, whichever is lower, you will have to give the owner an updated written estimate. The estimate must reach the owner by the end of the next working day at the latest. The threshold is about the recommended treatment pathway, not a single line item, so a course of treatment that crosses £500 in total triggers the requirement even if no individual element does.

That is the rule in one paragraph (for how it sits alongside the Order's other duties, see the complete guide to the CMA rules for vet practices). The rest of this guide covers what counts toward the threshold, when the update obligation bites, when the duty actually starts for a practice your size, and how to make the process reliable rather than something the team has to remember case by case.

What the Order actually requires

Article 11(1) of the Order sets the duty. A practice providing first-opinion or out-of-hours services "must give Pet Owners a written estimate of the reasonably likely costs of a Treatment Pathway" where the vet estimates that "the total cost of the Treatment Pathway is reasonably likely to meet or exceed the Monetary Threshold" and "the element of the total cost in (a) that relates to costs that may be incurred in the future exceeds 20% of the Monetary Threshold."

The Order defines the starting threshold as "£500 inclusive of VAT."

On the update obligation, Article 11(9) requires an updated written estimate "if the total estimated cost of the Treatment Pathway is reasonably likely to increase, from the amount in the original Written Estimate, by 20% or by an amount equal to the Monetary Threshold, whichever is lower."

Four things are worth drawing out of that wording:

• "Inclusive of VAT" is explicit. The threshold is the price the owner pays, not the ex-VAT figure. A treatment quoted internally at £430 plus VAT is over the line.
• "Treatment Pathway" means the recommended course of care, not a procedure code. Diagnostics, the procedure, medication, and follow-up that the vet is recommending together count toward the £500.
• The future-cost condition. The estimate is owed only where more than 20% of the threshold, so more than £100 at today's figure, relates to costs still to be incurred. The duty is aimed at the decision the owner still has to make, not at a bill for work already done.
• "Reasonably likely" sets the test at the point of recommendation, using the clinician's judgment. It does not require certainty — it requires a genuine estimate of the likely cost.

If you have read the CMA's guide, go by the Order. The CMA's guides for small and large veterinary businesses both word two parts of this rule differently from the Order. They describe the second condition as "at least 20% of that reasonably likely cost relates to tests and/or treatments that have not yet been provided or chosen by the Pet Owner", while the Order measures more than 20% of the £500 threshold. They also say no estimate is needed where the pet needs urgent treatment and a delay to write one would harm its welfare, while the Order (Article 11(8)) lifts only the timing rule and still requires an estimate once the emergency has ended, if further costs are likely to exceed 20% of the threshold. Each guide says "You should not rely solely on this guide." The Order is the binding text, so this page follows it.

The £500 will change. From 1 April 2028 the Order raises the threshold each year in line with CPI, in steps of £50, and the CMA publishes the figure that will apply by 14 February each year. Configure the trigger as a value you can update, not a hard-coded £500.

When the estimate has to be given

The Order sets a deadline as well as a trigger. Under Article 11(7) the written estimate must be given in enough time for the owner to consider it and seek an alternative estimate if they want one, and "no later than the end of the Working Day following the day on which the relevant Veterinary Professional recommended the Treatment Pathway."

Two exceptions are worth knowing precisely:

• Emergencies change the timing, not the duty. Where the vet judges that the pet needs urgent treatment and any delay would seriously affect its health and welfare, the timing rule does not apply. If further tests or treatment are then reasonably likely to cost more than 20% of the threshold, the Order says the practice "must instead provide a Written Estimate as soon as reasonably possible after the Emergency Situation has ended."
• The owner can decline. Article 11(3) disapplies the duty where a pet owner has expressly confirmed that they do not want a written estimate. Record that confirmation.

When the update obligation bites

The "20% or £500, whichever is lower" wording is where practices will most easily slip. The point at which you owe an updated estimate depends on the size of the original:

• On a £600 estimate, 20% is £120 — lower than £500 — so an update is owed once the likely cost rises by £120, to around £720.
• On a £3,000 estimate, 20% is £600 — higher than £500 — so the lower figure governs, and an update is owed once the likely cost rises by £500, to around £3,500.

The practical effect: on smaller estimates the percentage trigger applies; on larger ones the flat £500 trigger applies. The updated estimate must be given as soon as reasonably possible after the practice becomes aware it is needed. It must also show what the owner has already paid for and what they are likely to need to pay for, and state that it supersedes the earlier estimate.

When this starts to apply to your practice

This is the question that decides how much time you actually have, and the answer depends on the size of your business rather than on a single sector-wide date.

The CMA made the Order on 22 September 2026. Its Article 3 table sets the compliance date for written estimates as:

Your practice	Order compliance date (Article 3)
15 or more FOPs and/or out-of-hours centres ("Large Veterinary Business")	22 June 2027
Fewer than 15 FOPs and/or out-of-hours centres ("Small Veterinary Business")	22 September 2027

Two points an independent practice should take from that:

• You almost certainly fall in the "smaller" group. The Order draws the line at 15 first-opinion practices (FOPs) and out-of-hours centres combined, so a single-site or small-group independent practice is on the later date, the longest runway in the package.
• The dates are now fixed. Before the Order was made, these were indicative months. They are now dates in the Order itself, and you must comply from the next working day after yours.

That is a genuinely long runway, and the reason to start earlier is not the deadline. It is that the estimate duty is the one remedy in this package that changes clinical behaviour rather than a webpage, and behaviour takes longer to shift than a price list does.

Building the £500 rule into clinical workflow

The compliance risk here is not understanding the rule — it is catching it consistently in a busy consult. A process that depends on a clinician remembering the threshold mid-appointment will fail audit. A few controls make it reliable:

1. Estimate at the point of recommendation. Generate the written estimate when the vet recommends the pathway, not at checkout. The Order's test is set at the recommendation stage, and the latest it can go out is the end of the next working day.
2. Make the threshold a system prompt, not a memory test. If your practice management system can flag when an estimate reaches £500 including VAT, use it. If not, a desk-level rule ("any recommended pathway over £500 gets a written estimate before it starts") covers it.
3. Keep the record the Order asks for. Article 11(11) requires you to keep a copy of each written estimate, and a record of any significant factors that could change it, for at least 12 months after it was given.
4. Define the re-estimate trigger. Give the team the "20% or £500, whichever is lower" rule as a one-line decision aid, and a route to issue the updated estimate quickly when scope changes mid-treatment.
5. Write the SOP. Fold the estimate process, including the emergency and opt-out routes, into your SOP framework so it is documented, version-controlled, and trainable for new staff.

Common gaps to close

• VAT ignored. Estimating on ex-VAT figures pushes some pathways under the threshold on paper but over it in reality. Estimate on the VAT-inclusive total.
• Pathway split into parts. Quoting diagnostics, procedure, and medication separately so none individually hits £500 does not avoid the rule — the test is the recommended pathway's total likely cost.
• Estimate sent too late. An estimate that goes out after the next working day misses the Order's deadline, even if it is accurate.
• No update process. Practices put effort into the first estimate and none into the update. The 20%/£500 trigger will be a live obligation throughout the treatment, not a one-off at the start.
• Verbal only. A spoken figure is not a written estimate. The requirement is explicitly for it in writing.

How estimates fit the wider CMA package

The written-estimate rule is one of several CMA remedies a practice has to operationalise together. It sits alongside published price lists, prescription fee caps, ownership disclosure, and a documented complaints process. Sequencing all of them is what the CMA preparation timeline is for, and the CMA compliance self-assessment tool flags which of them your practice still has open. Treated as one workstream within your clinical governance framework — rather than five separate scrambles — the package is manageable for an independent practice.

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Reviewed 26 October 2026. The CMA made the Veterinary Services Market Investigation Order 2026 on 22 September 2026 and it came into force on 23 September 2026. The threshold, the update trigger, the timing rules and the compliance dates above are quoted from the Order itself, not from the draft consulted on in July and August 2026. This is general compliance information, not legal advice. Verify the current position against the Order and its Explanatory Note and the CMA's guide for small veterinary businesses (14 or fewer practices) or large ones (15 or more), and consult your defence body for practice-specific advice.