Key Highlights

  • The London Stock Exchange published a feedback statement on 21 November 2025 setting out deregulatory changes to the AIM Rules, including allowing dual-class share structures.
  • AIM has shrunk from a peak of 1,694 companies in 2007 to just 679 by March 2025, the lowest level since 2001, with takeovers the single biggest cause of departure.
  • Business relief on AIM shares for inheritance tax is being cut from 100% to 50% from 6 April 2026, producing an effective 20% inheritance-tax charge on death.
  • PISCES, a new venue for trading private-company shares, received FCA approval on 26 August 2025, positioned as a 'funding continuum' from private to public markets.
  • The number of nominated advisers has fallen to around 23, down from a 2009 peak of 68, thinning the gatekeeper layer AIM depends on.

Once the jewel of London's equity scene, the Alternative Investment Market has spent two decades shrinking. Now the London Stock Exchange and the FCA are betting that lighter rules, a new private-share venue and pension reform can halt the retreat.

The central development

The London Stock Exchange has launched the most substantial overhaul of its junior market in years. On 21 November 2025 it published a feedback statement setting out sweeping deregulatory changes to the AIM Rules, some taking effect immediately and others earmarked for a formal consultation in the first half of 2026. It is the clearest signal yet that the exchange intends to fight for AIM's survival rather than let it wither.

The package is deliberately founder-friendly. Companies with dual-class share structures that meet Main Market standards can now join AIM, a move designed to attract control-conscious entrepreneurs. Reverse-takeover rules have been softened so that acquisitions aligned with a firm's existing business need not trigger a full re-admission. Issuers may now present historical accounts under UK GAAP (FRS 102) rather than converting to IFRS, and secondary issuances of new share classes no longer require an admission document. Further ahead, the exchange is consulting on raising the threshold for a significant transaction from 10% to 25% and redesigning admission documents. Separately, changes to the rules for nominated advisers, or nomads, took effect on 4 June 2026.

Background: what AIM is and how it got here

Launched in 1995, AIM was conceived as a lightly regulated ladder for smaller, growth companies too young or too small for the Main Market. For years it worked, nurturing household names and drawing thousands of listings. But the market has been contracting for most of two decades, and the pace has quickened.

The numbers

The numbers are stark. AIM peaked at 1,694 companies in 2007. By March 2025, according to UHY Hacker Young, the figure had fallen to 679, the lowest since 2001, after a net loss of 61 companies in a single year against just 10 IPOs. Reuters reported 89 delistings in 2024 against only 18 new joiners. Takeovers have become the single biggest cause of departure: UHY counts 767 companies lost to bids over 20 years, roughly 36% of all delistings. Peel Hunt has estimated that around a third of AIM companies valued between £50m and £250m are vulnerable to a bid. Liquidity is thin, valuations are depressed, and UK-focused equity funds have endured more than 40 consecutive months of outflows.

The tax blow

Timing could scarcely be worse, because a key prop is about to be kicked away. In the Autumn Budget of October 2024 the government announced that business relief on AIM shares would be cut from 100% to 50% from 6 April 2026. For years, qualifying AIM shares held for two years passed free of inheritance tax, a perk that drew billions into dedicated IHT portfolios. From April, only half the value is relieved, producing an effective 20% inheritance-tax charge on death. Analysts fear the change will drain a captive pool of patient capital just as the exchange tries to rebuild confidence.

The rescue measures

The reform effort runs wider than the AIM rulebook. The centrepiece of the broader strategy is PISCES, the Private Intermittent Securities and Capital Exchange System, a new type of venue for intermittent trading in private-company shares. On 26 August 2025 the London Stock Exchange became the first operator to receive FCA approval to run a PISCES platform, under a regulatory sandbox that the FCA expects to make permanent by 2030. The exchange frames PISCES as part of a "funding continuum" from private to public markets, giving fast-growing firms a halfway house before a full listing.

Alongside sit the government's capital-markets reforms. Ministers have pressed pension funds to allocate more to UK equities and are reshaping the ISA regime, trimming the generosity of cash savings to nudge money toward investment. From April 2027, cash held within stocks-and-shares ISAs faces a new charge, part of a wider drive announced around the Mansion House set-piece to funnel household savings into productive assets. Whether any of this reaches AIM specifically remains an open question.

Implications for companies and investors

For companies, the reforms promise lower cost and friction. Listing on AIM is expensive, with initial costs of roughly £600,000 and annual upkeep near £500,000 by the British Business Bank's reckoning, so lighter documentation and fewer mandatory opinions could keep marginal issuers on the market. For founders, dual-class shares offer a way to raise capital without ceding control. For investors, the picture is mixed: deregulation may improve supply and pricing, but the loss of full IHT relief removes a powerful reason to hold AIM stock, and thinner rules could raise governance risk in a market already prone to blow-ups.

Competitive and industry context

The competitive backdrop is unforgiving. New York's deep, liquid markets continue to tempt the largest UK-listed names, while private capital, from venture funds to private equity, now keeps companies private for longer and buys public ones cheaply. AIM's shrinkage is partly a symptom of that global shift away from small-cap public equity, not a purely British failing, which is why some question whether tinkering with rules can reverse a structural tide.

Risks and uncertainties

There are real risks. Deregulation invites the charge that London is loosening standards in a market with a chequered history of failures. The nomad system itself is under strain: the number of nominated advisers has fallen to around 23, down from a 2009 peak of 68, thinning the gatekeeper layer on which AIM depends. And none of the reforms directly addresses the demand problem, that too few buyers want UK small-caps. As UHY Hacker Young's Colin Wright put it, the pendulum had swung too far toward overregulation and the exchange has started to fix that, but rules are only half the equation.

What to watch

Watch the H1 2026 consultation and whether the exchange follows through on raising the significant-transaction threshold and slimming admission documents. Watch the first live PISCES transactions for proof the private venue can generate genuine liquidity. Watch AIM's company count through 2026 for any sign the bleeding has slowed. And watch flows after 6 April, when the reduced inheritance-tax relief takes effect, for the clearest test of whether London can, in fact, save AIM.