Guidance

Interim measures in merger investigations: summary for businesses

Updated 23 June 2025

During an investigation, the CMA may require merging businesses to:

• pause work to integrate their operations
• continue to compete with one another

These requirements concern restrictions imposed by the CMA and are additional to any restrictions that may apply to conduct under competition law.

We enforce these requirements by imposing temporary legal orders called ‘interim measures’. We usually put these restrictions on businesses that complete their merger either before or during the CMA investigation.  

Consider the likelihood of a CMA investigation, and the possible effect of these restrictions, before deciding whether to complete a merger without telling the CMA.

Why we impose interim measures

You do not have to tell the CMA about your merger or get clearance before completing.

However, we can investigate a merger, even if it has completed recently, if we think it may lead to competition concerns.

If businesses have completed their merger, they might have already stopped competing and started to integrate their operations. If this happens before or during a CMA investigation, it could affect our ability to investigate the merger and our ability to address any competition concerns that we find.

Our interim measures aim to keep the merging businesses operating separately so we can:

• complete our investigation
• unwind the merger or take other action (for example, requiring part of the business to be divested), if we conclude that the merger raises competition concerns

Tell the CMA about your merger.

When we impose interim measures

The CMA usually imposes interim measures on businesses that complete their merger before we start our investigation.

If you decide to complete your merger during an investigation, we will act quickly and impose restrictions as soon as the merger is complete.

In most cases, we will remove the restrictions when we are confident that there will be no competition concerns or, if there are concerns, that they have been remedied effectively.

What we may restrict

The restrictions the CMA imposes on merging businesses can change during its investigation. Usually, we impose a standard set of restrictions on both businesses.

These include:

• maintaining separate sales and brand identity
• continuing to supply the same range of goods and services as before the merger
• retaining important staff members, and not moving staff between the merging businesses
• not sharing confidential or commercially sensitive information between the merging businesses

You can ask us to change the restrictions

Merging businesses must get permission from the CMA to do anything that is restricted by the interim measures. If you formally request our approval to do certain things, we might allow it – we call this permission a ‘derogation’.

We assess these requests on a case-by-case basis, considering the:

• nature and urgency of the request

• importance of what you propose to do

• potential effect on our investigation

Provide as much detail as possible about what you’re looking to do and discuss it with us early. This will help our assessment.

Use our derogation request template (ODT, 30KB) to submit a request to us.

What you need to do

The CMA may ask you to provide important information before imposing restrictions, for example about your ownership or corporate structure. This is so we impose restrictions on the correct parts of your business.

After we impose restrictions, we usually expect you to set out what steps you’ll take to follow them. For example, we expect you to:

• communicate internally with the relevant staff, and provide guidance or training on how to comply with the restrictions
• tell us if anything important changes that could affect the restrictions, such as you losing important staff or contracts

You must also submit a statement to us regularly, signed by a senior employee from each business (usually the CEO or another suitable employee agreed with the CMA). The statement will ask you to:

• confirm that you are complying with the restrictions
• tell us about possible failures to comply with the restrictions

An example compliance statement is available in our initial enforcement order template (PDF, 217KB).

What might happen if you do not follow the restrictions

We take merging businesses’ compliance with any imposed restrictions very seriously.

Not complying may delay the CMA’s investigation, or how quickly we can address any potential competition issues.

If we are concerned about your compliance, we may impose stricter restrictions on you. In some cases, we may require you to employ another company to report on your compliance (known as a ‘monitoring trustee’).

We might also:

• require you to undo any integration that we did not permit, which could be costly and inconvenient
• impose a large fine on you

Find more information

Go to Merging your business to find more information for merging businesses.

Go to Interim measures and derogations in merger investigations.