Moving on up: the why, the why not to and how of London AIM to Main Market transfers

In July 2024, the UK Listing Rules (UKLRs) replaced the premium and standard listing segments with the equity shares (commercial companies) category (ESCC).

This change sparked increased interest from larger AIM-quoted companies in moving to the Main Market of the London Stock Exchange (LSE). So far in 2025, three companies – including Brooks Macdonald Group and Elixirr International – have moved with one more, Johnson Service Group, having announced its intention to follow suit.

Why move to the Main Market?

Prestige and increased market confidence

The Main Market is London's and Europe's premier listing venue, offering increased prestige and, as investors typically consider Main Market issuers to offer lower investment risk, greater confidence in the issuer's performance compared to AIM. For ambitious boards, the move could be compelling.

Inclusion in indices and access to tracker funds

Only Main Market issuers are eligible for inclusion in indices such as the FTSE 100 or FTSE 250, opening up access to investment from tracker funds and institutions unable to invest in AIM stocks, potentially driving share price growth. 

Greater analyst coverage

Main Market issuers garner more interest from sell-side research analysts, boosting information flow, press coverage and profile.

Recognition of corporate development

AIM has a great pedigree of supporting growth companies achieve their goals and in so doing creating shareholder value. For example, Elixirr's market capitalisation has grown from £98.1 million at the time of its initial public offering (IPO) on AIM (July 2020) to around £325 million as at 1 July 2025 (being the date of Elixirr's admission to the Main Market), signifying its maturity and readiness for the next stage of its development. 

Experience on AIM allows issuers to acclimatise to the increased rigours and obligations associated with being a public company. As a result, the move to the Main Market (and the consequential increase in scrutiny and compliance burden) is less intimidating than it would be to a new applicant to public markets.

Both of the remainder of the current 2025 cohort have used AIM as a launchpad: Brooks Macdonald's market capitalisation grew from £13.7 million at its 2005 AIM IPO to approximately £246.2 million upon Main Market admission in March 2025.

Convergence of rules

Market participants anticipate a comprehensive response from AIM to the new UKLRs, following the closure of a consultation period initiated by an initial discussion paper published by the LSE on 7 April 2025.  With the removal of several onerous requirements from the previous premium listing segment by the UKLRs (discussed below), the regulatory regimes for companies on each market are now more aligned.  Indeed, in certain cases, the UKLRs are more favourable to issuers than the AIM Rules for Companies (for example, on the Main Market, an announcement will only be required for transactions above 25% in any class test (whereas the threshold is 10% on AIM)). It should be noted, however, that this was the subject of a question posed by the LSE in the April discussion paper and so the position may change in the future. 

Opportunity to raise capital

Boards may wish to use the step up to undertake a fundraise, either contemporaneously or post-transaction (by such time it would be hoped that, given the advantages listed above, any such fundraise might be at a higher valuation than could be achieved prior to the move). Boards should carefully plan the timing and strategy for such fundraises to maximise their benefits and achieve strategic aims.

What is the process involved?

Simplified prospectus

A company seeking admission of its shares to the Main Market must publish a prospectus. However, if the shares have been quoted on AIM for 18 months or more, the simplified prospectus regime under article 14(1) of the UK Prospectus Regulation can be utilised, reducing the production costs and timeframes. In either case, in a departure from how admission documents are prepared, the Financial Conduct Authority will review, comment on and need to approve the draft prospectus before it can be published. This review process should be built into the timetable of any move to the Main Market.

No shareholder approval required?

Normally, delisting form AIM requires the passing of a special resolution (75%) by shareholders. However, AIM Regulation may grant a derogation from rule 41 of the AIM Rules for Companies moving to the Main Market (as shareholders will retain the ability to trade their shares on a public market), simplifying the process and reducing execution risk. 

Eligibility requirements

Set out in UKLR 5, the eligibility requirements for the ESCC sit in between the criteria used previously for the premium and standard listing segments. These include:

• Market capitalisation. The issuer must have a market capitalisation of, at least, £30 million at admission. That said, issuers with a market capitalisation of less than approximately £250 million may be deemed too small to pursue a move to the Main Market.
• Free float requirements. At least 10% of the issuer's shares need to be held in public hands, whereas, on AIM, there is no such minimum requirement, instead the nominated adviser must opine on the issuer's overall suitability considering factors such as the free float.
• Independence from controlling shareholder. While a controlling shareholder agreement is no longer required, issuers must be able to articulate how they are able to carry on their main business activity independently from any controlling shareholder (that is a shareholder who exercises or controls 30% or more of the voting rights, either on their own or together with any person with whom they are acting in concert) in the prospectus and, therefore, many issuers may likely still keep such agreements in place with controlling shareholders.

One of the stated aims of the UKLRs is to encourage a more diverse range of issuers to list and for applicants to do so at an earlier stage of their development. As a result, several of the premium listing requirements have not been carried forward under the UKLRs, including the requirement for a clean working capital statement, a minimum three-year track record and historical financial information.

Articles of association

Boards should review their existing articles of association to ensure they are suitable for a Main Market company. Areas of interest will include provisions concerning the election and re-election of directors (for example, the annual retirement of all directors at each AGM (as required for full compliance with the UK Corporate Governance Code published by the Financial Reporting Council and, where there is a controlling shareholder, the dual vote requirement for the election and re-election of independent directors set out in UKLR 6.2.5R). 

Boards will also want to ensure that any borrowing limits set out in the articles remain appropriate given the development of the company and may wish to take the opportunity to make certain other amendments (including any modernising changes such as permitting hybrid shareholder meetings).

Sponsor role

Issuers must appoint a sponsor to advise in relation to the move up. The sponsor will be responsible for ensuring that the company has complied with the various listing and prospectus content requirements and that it can comply with its continuing obligations as a Main Market company. The role of the sponsor is more limited than that of the AIM nominated adviser.  Issuers are not required to retain a sponsor on a day-to-day basis, saving them the annual nominated adviser fee (albeit broking fees will continue to apply). Many nominated advisers can also fulfil the role as sponsor.  However, boards should take care in selecting the correct sponsor for this next stage of the company's development.

Reasons to stay on AIM

Loss of inheritance tax relief

A move to the Main Market means the loss of inheritance tax relief available on AIM. Boards must consider their shareholder register before committing to the move.  IHT funds will use the time between any formal announcement of the intention to move and the date of the transfer to sell their holdings. Depending on the materiality of such holdings and general liquidity in the shares, these sales might have a negative effect on the share price.

Corporate governance regime

Main Market companies must apply the UK Corporate Governance Code, which is more onerous than the QCA Corporate Governance Code adopted by the majority of AIM companies. Despite the 'comply or explain' approach, companies should be prepared for the increased governance requirements.

Controlling shareholder

Arrangements with controlling shareholders face greater scrutiny on the Main Market, where the market can be less understanding of such arrangements than they are on AIM. Some controlling shareholders may not wish to put these arrangements in the spotlight. 

Greater interaction with institutional investor bodies

A move to the Main Market will bring companies more firmly into the remit of certain institutional and adviser guidelines (including those issued by the Investment Association, the Pensions and Lifetime Savings Association and PIRC), as well as proxy advisors such as Glass Lewis and ISS. Compliance with these guidelines and requirements can be onerous.

Increased scrutiny and expectations

Main Market companies are subject to heightened scrutiny from analysts, institutional investors and regulatory bodies, which can lead to increased pressure and expectations. Remaining on AIM can provide companies with the necessary breathing room to develop and expand at their own pace without the pressure to meet the rigorous standards and expectations of the Main Market. This can be particularly advantageous for companies that are still in the growth phase of development. 

Increased ongoing costs

Annual costs for a Main Market listing can be double those on AIM, varying based on factors such as market capitalisation, business complexity and service providers. Boards should therefore conduct a thorough cost-benefit analysis to ensure the move is financially viable.

Osborne Clarke comment

A move from AIM to the Main Market can be highly beneficial for mature AIM-quoted companies with robust internal processes. Enhanced profile, access to a wider pool of investors and increased liquidity are significant advantages. However, this move may not be suitable for all companies. 

If you are considering this transition, please contact any of the authors below or your usual Osborne Clarke contact to discuss your specific needs in greater detail.