The International Order Book (IOB) is a dedicated electronic trading segment on the London Stock Exchange for global depositary receipts (GDRs) — certificates issued by a depositary bank that represent shares in a company incorporated outside the UK. Rather than listing ordinary shares directly, companies from markets such as Central and Eastern Europe, Asia and the Middle East use GDRs to make their equity accessible to international investors through a single, US dollar-denominated order book in London.
Companies that use GDRs often come from markets with capital controls, foreign-ownership limits, or listing requirements that can make a full primary listing abroad impractical — a GDR structure sidesteps that by letting a local custodian hold the underlying shares while a depositary bank issues a tradeable certificate overseas. The London Stock Exchange launched the IOB in 2001 to concentrate this GDR liquidity in one venue, rather than leaving it scattered across over-the-counter arrangements, so that investors in different time zones could reach these securities through one transparent, centrally cleared book.
Mechanically, the IOB works like the Exchange's other electronic markets: it is a central limit order book, matching buy and sell orders continuously and running opening, intraday and closing auctions at set points in the trading day. Trading runs from 8:00am to 4:30pm, aligned with the Main Market, and every instrument on the IOB is priced and settled in US dollars rather than sterling. Lot sizes, tick sizes and circuit-breaker auctions follow the same Millennium Exchange trading-system rules that govern the rest of London Stock Exchange's electronic markets, so a trader already familiar with SETS order types is not learning an entirely new mechanism — just a different currency and a different pool of underlying companies.
This is the distinction worth holding onto: the IOB is not a separate exchange or a separate rulebook so much as a separate order book layered onto the same infrastructure. The Main Market's central order book (SETS) trades ordinary shares of UK and international companies that have taken a primary or standard listing in London, priced mostly in sterling. The IOB, by contrast, trades only GDRs — a step removed from the underlying shares themselves — priced in dollars, and drawn from companies that have not necessarily listed in London at all.
A related but distinct confusion is GDRs versus American Depositary Receipts (ADRs). The US Securities and Exchange Commission defines an ADR as a security representing shares of a non-US company that are held by a US depositary bank outside the United States, registered with the SEC and traded on US exchanges. A GDR on the IOB follows the same basic structure — a depositary bank holding the underlying shares while a receipt trades elsewhere — but the receipt is cleared through London rather than US clearing systems. The two aren't mutually exclusive: some issuers use a GDR alongside a US ADR programme rather than instead of one, depending on where they want investor access.
The clearest recent illustration is the Shanghai–London Stock Connect scheme, under which Chinese A-share companies issue GDRs that trade on a dedicated Shanghai segment of the IOB — giving international investors dollar-denominated access to mainland Chinese equity without a direct A-share account. The scheme has not grown as quickly as its 2019 launch envisioned: as of early 2025, reporting put the number of Chinese issuers that had used it at around six, with no new listing since mid-2023. It remains a live example of the IOB's function even so — a bridge that lets a market with restricted direct access reach international investors through London's order book. Geopolitics can also close that bridge from either direction — European and UK sanctions imposed since 2022 in connection with Russia's invasion of Ukraine led the Exchange to suspend trading in GDRs of most Russian-incorporated issuers, including several that were previously among the IOB's most actively traded names, a reminder that IOB access depends on regulatory permission as much as commercial demand.
If a security is described as trading "on the IOB," that phrase already tells you three things: it is a GDR, not the underlying ordinary share; it prices in dollars, not sterling; and it sits outside SETS, the Main Market's own order book. Confirm those three points and the rest of the mechanics — auction times, lot sizes, clearing — follow the same rules as any other electronic London Stock Exchange market.
What is the International Order Book of the LSE?
The IOB is the London Stock Exchange's dedicated electronic order book for global depositary receipts (GDRs) — certificates representing shares in companies incorporated outside the UK. It trades in US dollars, runs alongside the Main Market's own order book, and currently covers GDRs from over 30 countries.
How does a central limit order book work?
A central limit order book collects all buy and sell orders for a security in one place and matches them by price and time priority, so the best-priced orders are filled first. The IOB uses this mechanism, running continuous matching during the trading day plus scheduled opening, intraday and closing auctions to set prices when the book isn't in continuous trading.
Is it better to buy at a market order or a limit order?
Neither is universally better; they trade off different things. A market order executes immediately at the best price currently available but doesn't guarantee what that price will be. A limit order guarantees the price (or better) but doesn't guarantee the order will execute at all if the market never reaches it. Which one suits a given trade depends on whether execution certainty or price certainty matters more in that moment.
Can I sell a stock above my limit order?
Yes. A sell limit order sets the minimum price you're willing to accept — it will only execute at that price or higher, never below it. If the market price is above your limit when the order is matched, you receive the better (higher) price, not the limit price itself.
Is the London Stock Exchange still open?
Yes. The Main Market and the IOB both trade Monday to Friday, 8:00am to 4:30pm London time. The Exchange has continued to develop new trading infrastructure — in 2026 it announced LSE 24, a near-continuous 24/5 venue intended to run alongside, not replace, existing market hours.
