What Is AIM and How Can You Trade or Invest in It?
The Alternative Investment Market (AIM) is a sub-market of the London Stock Exchange (LSE), designed to give small and growing companies easier access to public capital. It was introduced to replace the Unlisted Securities Market and support early-stage businesses that couldn’t meet the full listing requirements of the Main Market.
Established in 1995, AIM provides a more flexible regulatory environment than the Main Market, allowing younger companies to float shares publicly with reduced listing costs and lighter reporting obligations.
Though it launched with just 10 companies and a market capitalisation of £82 million, AIM has helped over 4,000 companies raise more than £135 billion since inception, contributing significantly to UK GDP and employment — and built an ecosystem of advisers including nominated advisers, brokers and market makers, who have built their own businesses around the index.
What sets AIM apart is its principles-based regulatory system based on flexibility and access over red tape. While this approach attracts entrepreneurs and investors with higher risk tolerance, it also introduces unique challenges, particularly surrounding transparency, oversight and liquidity.
For context, AIM’s performance has varied over the years. In the mid-2000s, it saw rapid growth and global popularity, but more recently the number of listings has declined sharply. Regulatory reforms, macroeconomic uncertainty, and reduced investor appetite for small-cap risk have contributed to this slowdown, and as of mid-2025, AIM has fewer than 700 actively listed companies, compared to a peak of over 1,600 in 2007.
But despite recent declines in IPO volumes and increased investor uncertainty, AIM remains a unique platform for dynamic, high-potential businesses. And arguably, its listings could recover sharply in the event that the current market demand for larger companies falls.
