The London Stock Exchange is the UK’s primary stock market – home of the Main Market, AIM, and the companies inside the FTSE 100. It is also changing faster right now than at any point in recent memory. The listing rulebook was rewritten in 2024, the prospectus regime was replaced in January 2026, a T+1 settlement date is locked in for 2027, and a 24-hour trading venue was announced two days before I wrote this.
Which means most LSE guides on the internet are now wrong. If an article mentions “Premium and Standard listings” or “the UKLA,” it is describing an exchange that no longer exists.
This guide is current as of July 2026. Every figure that moves carries its as-of date, because context in markets is everything – and a number without a date is a rumor, not context.
What the London Stock Exchange actually is
Legally, it is London Stock Exchange plc, a wholly-owned subsidiary of London Stock Exchange Group plc (LSEG). LSEG is itself listed on the Main Market, so the parent trades on the exchange it owns (a fun bit of recursion). The exchange is a Recognised Investment Exchange (RIE) under FSMA, supervised by the FCA against its REC sourcebook.
Keep LSEG and the LSE separate in your head. LSEG is the group; the exchange is one business inside it. FTSE Russell, which calculates the FTSE indices, is another LSEG business – and it is not the exchange either. Mixing these up leads to real errors, like confusing LSEG plc’s own market cap with the value of every company listed in London.
On global standing, plainly: UK domestic market capitalisation is roughly $4.0-4.1 trillion (May 2026). By some measures the LSE dropped out of the World Federation of Exchanges’ global top 10 by domestic market cap during 2026, having ranked around 6th as recently as May 2025. And Europe’s largest exchange is Euronext, at around $8.7 trillion (March 2026) – not the LSE. Plenty of older articles still hand London that crown. The numbers don’t.
The markets: Main Market, AIM, and the rest
The Exchange operates one regulated market and two MTFs (multilateral trading facilities), plus a brand-new private-company venue:
- Main Market – the UK regulated market. Issuers are admitted to the FCA’s Official List. It includes the Specialist Fund Segment.
- AIM – an MTF for growth companies. AIM securities are not on the Official List, a distinction with real regulatory and tax consequences.
- A second MTF carrying the International Securities Market (ISM, professional investors only), the Professional Securities Market (PSM), and Admission to Trading Only (ATT). Since January 2026, no new class of securities can be admitted to the PSM.
- Private Securities Market – a PISCES venue for trading private-company shares, sitting outside the Admission and Disclosure Standards (more on this below).
The Sustainable Bond Market and Voluntary Carbon Market are designations applied to admitted securities, not separate markets.
And one naming correction, because so many guides get it wrong: the UK listing authority is the FCA. “UKLA” and “UK Listing Authority” are defunct branding. The rulebooks in force today are the UK Listing Rules (UKLR, since 29 July 2024), the Prospectus Rules: Admission to Trading on a Regulated Market (PRM, since 19 January 2026), the DTR, and UK MAR. The old LR and PRR sourcebooks no longer exist.
Listing on the Main Market (ESCC)
Since July 2024, most commercial companies list in a single category: equity shares (commercial companies), or ESCC, under UKLR 5. The requirements:
- Minimum market capitalisation of £30m
- Minimum free float of 10%
- A sponsor for new applicants
What’s striking is what’s gone. The old requirements for historical financial information, a revenue track record, and a clean working capital statement were all removed on 29 July 2024. Any guide telling you a Main Market listing needs a three-year revenue history is quoting rules that no longer exist.
Listing on AIM
AIM has no minimum market capitalisation, no minimum trading record, and no minimum free float. The binding requirement is a Nominated Adviser (a “Nomad”), retained at all times – lose your Nomad and your shares are suspended under AIM Rule 1. The one hard cash rule: investing companies must raise a minimum of £6m at admission.
How trading works
All times below are London local time – GMT in winter, BST in summer. Say this in your scheduler’s config, not just your head; it bites twice a year.
| Session | Time (London) |
|---|---|
| Opening auction call | 07:50 – 08:00 |
| Continuous trading (SETS) | 08:00 – 16:30 |
| Closing auction call | 16:30 – 16:35 |
| Closing price crossing | until about 16:40 |
Liquid names trade continuously on SETS, the electronic order book. Illiquid Main Market and AIM names trade on SETSqx, which is auction-only: four auctions daily at 09:00, 11:00, 14:00 and 16:35. Older sources list five auctions, including one at 08:00 – that’s stale.
Settlement is T+2 today. T+1 is confirmed for 11 October 2027, the first trading date for T+1 in UK cash equities. For context, the US made the same move on 28 May 2024.
LSE 24: announced, not live
On 21 July 2026, the exchange announced LSE 24, a separate 24/5 venue that will run 17:00 – 07:50 with a pause from 18:30 to 19:00. Client testing is planned for end-2026, with ETPs first in H1 2027 (subject to regulatory approval) and equities later. The Main Market keeps its existing 08:00 – 16:30 hours.
So no – the LSE does not have 24-hour trading today. But the plumbing is being built, and if you run data infrastructure, that future session window belongs on your radar now.
The pence problem: why LSE prices break data pipelines
If you bookmark one section of this guide, make it this one.
Most LSE share prices are quoted in pence sterling, written GBX (or GBp). One GBX is 1/100 of a pound. A stock quoted at 2715 is trading at £27.15 – not £2,715. Miss that, and every valuation, return, and market cap downstream is off by a factor of 100.
How dominant is pence quoting? On 23 July 2026 we pulled every Main Market share line from the LSE’s own Price Explorer – all 944 of them – and counted trading currencies:
| Trading currency | Main Market share lines (23 Jul 2026) |
|---|---|
| GBX (pence) | 870 |
| USD | 49 |
| EUR | 15 |
| GBP (pounds) | 7 |
| JPY | 3 |
Three things in that table hurt pipelines.
1. GBX is not a real ISO currency. ISO 4217 has only GBP; GBX is a market convention. So every vendor decides for itself how to represent pence, and they don’t agree – some return GBX, some GBp, some return GBP with a pence-denominated value, and some silently convert to pounds. The convention itself is fine once you know it. The inconsistency between vendors is what actually breaks pipelines: the same share can arrive as 2715 GBX from one feed and 27.15 GBP from another, and both are “correct.”
2. The reverse error is just as bad. The tempting fix is “divide every LSE price by 100.” Don’t. Seven Main Market share lines are quoted in real pounds (mostly preference stocks), and 67 more trade in USD, EUR or JPY. Blindly dividing those by 100 is the exact same 100x error, pointed the other way.
3. Precision matters more than you’d think. Sub-penny prices are live on the book – prices like 0.0215 USD and 1.7 GBX appear in the same pull. If your schema rounds to two decimal places, you just destroyed your small-cap and fund prices.
One bonus trap: index levels are neither pence nor pounds. The FTSE 100 in the 9,000s is measured in points.
The practical rule: never assume a currency for a UK instrument. Carry the trading currency per instrument line, treat GBX/GBp as pence explicitly, normalise once and deliberately, and store enough decimal places to survive. Clean data should be boring. LSE data only gets boring after you do this work – which is exactly why so few vendors do it well.
How big is the LSE?
Every figure here moves, so every figure gets a date.
Counting listings. As of 23 July 2026 the Main Market has 944 share lines, or 1,013 equity lines once you include IOB and depositary-receipt lines and the Specialist Fund Segment. AIM had 613 share lines the same day, and 619 companies at 31 December 2025 (530 domestic, 89 foreign).
A caveat, stated plainly: those are instrument lines, not companies. A company with two share classes counts twice. Treat them as solid order-of-magnitude, current-day figures. (And if a guide tells you the LSE has “about 2,000 companies,” it is roughly a decade stale.)
Counting value. The FTSE All-Share had a net market cap of £2,826,415m – call it £2.83 trillion – at 30 June 2026. Within that, the FTSE 100 accounts for about £2.49 trillion, the FTSE 250 for £295,872m, and the FTSE SmallCap for £38,070m. Two caveats travel with those numbers: “net” means free-float adjusted, so this is not the total value of every London-listed company, and the All-Share excludes AIM entirely. AIM’s own aggregate market cap was £64.52bn at 31 December 2025, down about 18% from £78.96bn at end-2023.
For the whole-market view, the figure is the one from earlier: UK domestic market capitalisation of roughly $4.0-4.1 trillion (May 2026).
The FTSE indices
First, an attribution fix: the exchange does not calculate the FTSE indices. FTSE Russell does – a business of LSEG, but distinct from the exchange operation. (FTSE index data is also licensed separately, which matters when you buy data.)
| Index | What it is | Details |
|---|---|---|
| FTSE 100 | The 100 largest companies by full market cap within the FTSE All-Share universe, screened for size and liquidity | Free-float weighted, reviewed quarterly; launched 3 Jan 1984 |
| FTSE 250 | The next 250 companies after the FTSE 100 | Launched 12 Oct 1992 |
| FTSE 350 | FTSE 100 + FTSE 250 | – |
| FTSE SmallCap | Smaller Main Market companies below the 350 | 186 constituents (30 Jun 2026) |
| FTSE All-Share | The broad UK benchmark; FTSE describes it as capturing 98% of the UK’s market capitalisation | 536 constituents (30 Jun 2026); base date 10 Apr 1962 |
Two things people routinely get wrong. The FTSE 100 is not a clean proxy for the UK economy – many of its constituents earn most of their revenue overseas. And the FTSE UK Index Series universe is Main Market only: AIM is excluded from every index above. AIM has its own series instead – the FTSE AIM All-Share, FTSE AIM 100, and FTSE AIM UK 50. If your “UK universe” is the All-Share, you are missing all of AIM.
What changed recently
A lot. This is why so much LSE writing is out of date.
The 2024 listing-rules overhaul
On 29 July 2024 the UKLR sourcebook replaced the old Listing Rules entirely – the FCA called it the most significant change to the UK listing regime in over three decades. The headlines:
- The Premium and Standard listing segments were abolished, merged into the single ESCC category.
- Shareholder votes are no longer required for significant transactions or related-party transactions. They were replaced by market notifications, plus a sponsor’s fair-and-reasonable opinion for related-party transactions at or above 5%.
- Votes were kept for reverse takeovers, buy-backs, non-pre-emptive discounted issuances, and cancellation of listing.
- Eligibility loosened (the track-record removals covered above), and dual-class share structures are permitted on more permissive terms.
- Legacy standard-listed shares sit in a closed transition category, UKLR 22.
The 2026 prospectus regime
On 19 January 2026, the POATRs plus the FCA’s PRM sourcebook replaced the old prospectus regime. Prospectuses are no longer FCA-approved for public-offer purposes, and the threshold for needing a prospectus on a further issue rose sharply.
Departures – and a counterweight
The delisting story is real, so here it is without spin. 88 companies delisted or moved their primary listing off the Main Market in 2024, the most since 2009. Familiar names among the leavers: TUI consolidated into a single German listing in February 2024; IBM cancelled its LSE listing effective 6 November 2024; Just Eat Takeaway cancelled its secondary listing effective 27 December 2024; Indivior followed on 25 July 2025; Ashtead Group redomiciled to the US as Sunbelt Rentals Holdings, NYSE-primary from 2 March 2026; Wise became Wise Group plc with a Nasdaq primary from 11 May 2026; and Flutter Entertainment delists fully, with a last LSE trading day of 31 July 2026 and delisting effective 3 August 2026.
The counterweight: 2025 was London’s strongest IPO year since 2021, with 11 IPOs raising about £1.9bn – more than double 2024’s roughly £700m. Both things are true at once, and any account that gives you only one of them is selling a narrative.
AIM: smaller, and mid-reform
AIM peaked at roughly 1,700 companies in 2007. It ended 2024 with 688 (the lowest since end-2001) and 2025 with 619. Two forces are at work. Tax: the 30 October 2024 Budget cut Business Property Relief on AIM shares from 100% to 50%, effective 6 April 2026, taking the effective inheritance-tax rate on qualifying holdings from 0% to about 20%. And reform: the exchange consulted on an AIM rulebook overhaul (AIM Notice 62, published 4 June 2026; consultation closed 2 July 2026), with final rules expected later in 2026 – not yet in force as I write.
PISCES and the Private Securities Market
The LSE was the first FCA-approved PISCES operator. Rules were published on 5 February 2026 and the first transaction took place on 25 March 2026. It is secondary-only trading in private-company shares – no new capital raising – and a genuinely new kind of venue worth watching.
Stamp duty and a data-fee change
Main Market share purchases attract 0.5% SDRT. AIM shares have been exempt since 28 April 2014. And from the 26 November 2025 Budget, shares of newly UK-listed companies are exempt from the 0.5% SDRT for three years from listing (for companies first listed on or after 27 November 2025). One more recent change – a retail market-data fee waiver from January 2025 – belongs in the next section.
Getting London Stock Exchange data
LSEG licenses LSE market data directly under a Real Time Market Data Agreement, and the cost has two layers: a redistribution licence (what a vendor or broker pays to carry the data) plus end-user charges (per-user monthly fees). Separate licence types cover non-display/algorithmic use, derived data, index calculation, and historical data. The product tiers are what you’d expect: Level 1 (top of book and last trade), Level 2 (full depth), post-trade, 15-minute delayed, and after-midnight.
Two genuinely user-friendly facts. Since January 2025, LSEG no longer charges monthly end-user fees for customers qualifying as Private Investors on real-time LSE and Turquoise data – real credit to them, because that is a meaningful give to retail. The precise part matters though: the redistribution licence still applies to the broker or vendor, so the waiver is on the per-user layer only. It is not “free LSE data for everyone.” Separately, 15-minute delayed post-trade data is free. And remember that FTSE index data is licensed separately, by FTSE Russell.
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The bottom line
The London Stock Exchange of 2026 is a different institution from the one most guides describe: one listing category instead of two, a new prospectus regime, a smaller but reforming AIM, a brand-new private-company venue, and a 24/5 venue on the way. Smaller than its past by some measures, moving faster than its reputation by most.
If you take away two things: date every LSE figure you rely on, and respect the pence problem – GBX has quietly broken more UK data pipelines than any exotic derivative ever will. The numbers in this guide will drift too. That’s why each one carries its date.
And if you’re building something with market data and care about getting it right at this level of detail, come say hi at tiingo.com. We love this stuff, and we’re always happy to help.