For a decade the complaint about British capital markets has been the same: companies stay private for longer, float later and increasingly choose New York over London when they finally do. The government’s answer is not another listing-rules tweak but a genuinely new category of market. It is called PISCES, the Private Intermittent Securities and Capital Exchange System, and by the summer of 2026 four operators had been approved to run one. It is the most novel piece of UK market plumbing in years, and it works by inverting the assumption that a stock market has to be transparent and continuous.
PISCES exists because the Treasury legislated it into being. The Financial Services and Markets Act 2023 (Private Intermittent Securities and Capital Exchange System Sandbox) Regulations 2025 created the framework as a regulatory sandbox, a bounded experiment that runs until 5 June 2030, at which point the Treasury must report to Parliament on whether it is working. The Financial Conduct Authority filled in the detail with its final rules, PS25/6, published in June 2025 and now sitting in a dedicated PISCES sourcebook. The design brief was explicit: bridge the liquidity gap between staying fully private and running a full public listing, and rebuild the pipeline of companies that might one day float in London.
A market that switches on and off
The word doing the work is intermittent. A PISCES venue does not trade continuously the way the main market or AIM does. Instead it hosts occasional, time-limited trading events, and it is the company, not the exchange, that decides when one happens. The company also decides who is allowed to take part, and it can set a floor and a ceiling on the price at which its shares change hands during the window. That is a deliberate reversal of how public markets work. On the London Stock Exchange’s main market a listed company cannot switch trading off, pick its buyers or cap the price. On PISCES it can do all three.
The transparency regime is inverted in the same way. Public markets run on disclosure to the world: a listed company’s price-sensitive information goes to every investor at once. PISCES runs on private disclosure. Companies must provide a core set of information mandated by the FCA, and platform operators can require more, but that information goes to the participants in the trading event rather than to the public. In effect PISCES trades the openness of a public market for the control of a private one, and asks investors to accept a narrower, bilateral flow of information in return for access.
Who can trade, and the tax that makes it work
Access is restricted by design. The permitted participants are institutional investors, high-net-worth individuals and self-certified sophisticated investors. Ordinary retail investors are largely kept out, and where they are involved they must receive personalised risk warnings through intermediaries. This is a market for insiders and professionals, not a retail venue.
The commercial glue is tax. The Treasury has used secondary legislation to exempt PISCES transactions from stamp duty and stamp duty reserve tax, aligning the treatment with the long-standing exemption for AIM shares. Without that relief a PISCES trade would carry the 0.5 per cent charge that applies to ordinary share transfers, and the venue would struggle to compete. The government has also published a technical note on the tax position of employees selling shares acquired through employee share schemes, which matters because one of the clearest use cases for PISCES is letting the staff and early backers of a fast-growing private company cash out part of their stake without forcing the whole business onto a public market.
The venues are live
This is no longer theoretical. The London Stock Exchange was approved to run its Private Securities Market as the first PISCES operator in August 2025, and JP Jenkins followed in November 2025. By April 2026 Asset Match and Vestd had both been approved, taking the number of live operators to four, and the first trades had taken place on the London Stock Exchange’s venue during 2026. The infrastructure the government wanted now exists and is running.
The open question is whether it feeds the pipeline
What no one can yet answer is whether PISCES does the job it was built for. The case for it is that a controlled, intermittent venue gives founders and early investors a pressure valve, some liquidity without the cost, scrutiny and loss of control of an initial public offering, and that companies which can offer that will stay in Britain and eventually list here rather than drifting to private-equity buyouts or overseas markets. The case against is that the same features that make PISCES attractive to companies, the ability to switch trading on and off, to choose the buyers and to keep disclosure private, are the ones that make a genuine, liquid, price-discovering market hard to build. A venue that trades only when the company wants it to, at a price the company can bound, may prove to be a comfortable permanent halfway house rather than a stepping stone to a full listing.
The sandbox structure means the government has built that uncertainty into the design. PISCES has until 2030 to show that it channels companies towards public markets rather than parking them just short of one. The plumbing is in place and the operators are open. Whether the shares actually flow, and whether the flow leads anywhere, is the thing the next four years will decide.
Sources: the Financial Services and Markets Act 2023 (Private Intermittent Securities and Capital Exchange System Sandbox) Regulations 2025 (SI 2025/583), establishing PISCES as a regulatory sandbox running to 5 June 2030 with a Treasury report to Parliament at its close; the FCA’s final rules PS25/6 (June 2025) and the PISCES sourcebook, setting the framework for intermittent trading events, company control over timing, participant eligibility and price parameters, core disclosure requirements and restrictions on retail participation; HM Treasury secondary legislation exempting PISCES transactions from stamp duty and stamp duty reserve tax in line with the AIM exemption, and the government technical note on the tax treatment of employees trading shares on PISCES; and FCA approvals of PISCES operators, the London Stock Exchange’s Private Securities Market (August 2025), JP Jenkins (November 2025), and Asset Match and Vestd (April 2026), with first trades taking place on the London Stock Exchange’s venue during 2026.
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