What is insider trading?

This guide explains the insider trading meaning under UK law, clarifies how terminology differs from other jurisdictions and outlines the penalties you could face. The aim is to help you understand what the rules are, why they exist and how they are enforced.

Disclaimer: This article provides general educational information about UK law. It does not constitute legal or financial advice. If you have specific concerns about your circumstances, consult a qualified legal professional.

Insider trading definition and key terms

Insider trading refers to dealing in securities while possessing inside information. The person trading has an unfair advantage because they know something material about a company or its securities that other market participants do not.

Several key terms underpin this definition:

• Insider: A person who possesses inside information, whether through their job, professional relationship or other means

• Securities: Shares, bonds, derivatives and other financial instruments traded on regulated markets

• Dealing: Acquiring, disposing of or attempting to acquire or dispose of securities

• Inside information: Information that is precise, not public, relates to securities or an issuer, and would likely affect the price if made public

The critical element is the information asymmetry. When one party trades on knowledge that others cannot access, the market stops being a level playing field.

What is inside information?

Understanding what is inside information is essential because the entire legal framework hinges on this concept. UK law sets out four cumulative requirements for information to qualify as inside information:

Examples of inside information include:

• Advance knowledge of an imminent takeover bid

• Unpublished financial results showing unexpected losses

• A major contract win not yet announced

• Regulatory approval or rejection of a key product

• Senior executive departures before public disclosure

Information remains inside information until it has been properly disclosed through official channels. Rumours or speculation, even if accurate, do not transform private knowledge into public information.

Insider trading vs insider dealing: UK terminology

You may encounter both terms used interchangeably, but there is a distinction worth noting. Insider dealing is the term used in UK criminal law, specifically under the Criminal Justice Act 1993. Insider trading is the broader, internationally recognised term that encompasses the same conduct.

In practice, when discussing UK enforcement, regulators may pursue insider dealing as a criminal offence or market abuse as a civil matter. The underlying conduct is the same: trading on inside information. The difference lies in how authorities choose to respond and the standard of proof required.

Why is insider trading illegal?

The question of why is insider trading illegal has a straightforward answer: it destroys market integrity. Financial markets function on the assumption that all participants have equal access to material information. When this assumption breaks down, several harms follow.

First, insider trading erodes investor confidence. If ordinary investors believe the game is rigged, they will participate less, reducing market liquidity and efficiency.

Second, it distorts price discovery. Prices should reflect all publicly available information. When insiders trade on private knowledge, prices move for reasons hidden from other participants.

Third, insider trading harms companies directly. Executives who trade on bad news before announcing it damage their firm’s reputation and may face shareholder lawsuits.

Fourth, it creates an uneven playing field that favours those with access over those with skill or diligence. This undermines the meritocratic premise of investing.

The prohibition is not arbitrary. It reflects a policy judgment that fair markets benefit everyone, including companies raising capital, investors seeking returns and the broader economy that depends on efficient capital allocation.

UK market abuse regulation: The legal framework

The UK market abuse regulation provides the primary civil and regulatory framework for tackling insider trading. Following Brexit, the UK retained a version of the EU Market Abuse, now known as UK MAR, with the onshored regime applying from the end of the transition period at 11pm on 31 December 2020.

UK MAR prohibits three main categories of market abuse:

• Insider dealing: Using inside information to deal in securities

• Unlawful disclosure: Improperly sharing inside information with others

• Market manipulation: Creating false or misleading impressions about supply, demand or prices

The Financial Conduct Authority (FCA) administers UK MAR and has broad powers to investigate and sanction breaches. Importantly, UK MAR applies to anyone who possesses inside information and trades on it, not just company directors or employees.

The regulation also imposes obligations on issuers. Companies must maintain insider lists, disclose inside information promptly and ensure that anyone with access to such information understands their responsibilities.

Alongside UK MAR, the Criminal Justice Act 1993 creates the criminal offence of insider dealing. This dual framework means authorities can pursue both civil sanctions and criminal prosecution, depending on the severity of the conduct and the evidence available.

Examples of insider trading

Examining insider trading examples helps illustrate how the law applies in practice. These hypothetical scenarios demonstrate the types of conduct that constitute offences.

Scenario one: A finance director learns that quarterly earnings will fall significantly below market expectations. Before the company announces the results, the director sells personal shareholdings. This is insider dealing because the director possessed precise, price-sensitive information not available to the public.

Scenario two: A lawyer working on a confidential takeover bid tells a friend which company is about to be acquired. The friend buys shares before the announcement. Both individuals may face liability: the lawyer for unlawful disclosure and the friend for trading on inside information.

Scenario three: An IT contractor installing systems at a pharmaceutical company overhears executives discussing failed drug trials. The contractor sells shares short before the public announcement. Despite having no formal role in corporate decision-making, the contractor possessed inside information and traded on it.

Scenario four: A journalist receives a tip about an impending merger and trades before publishing the story. Even though the journalist plans to make the information public, trading before publication constitutes insider dealing.

These examples share common features: precise information, lack of public availability, price sensitivity and trading that exploits the informational advantage.

Consequences and penalties in the UK

The insider trading punishment in the UK reflects the seriousness with which authorities treat market abuse. Penalties vary depending on whether authorities pursue criminal prosecution or civil enforcement.

Criminal sanctions

Under the Criminal Justice Act 1993, insider dealing is a criminal offence. Conviction requires proof beyond reasonable doubt that the defendant dealt in securities while possessing inside information.

Criminal penalties include:

• Imprisonment for up to 10 years

• Unlimited fines

• Confiscation of proceeds under the Proceeds of Crime Act 2002

• Criminal record affecting future employment and travel

Criminal prosecution typically targets the most serious cases, particularly those involving significant financial gain, repeated offending or abuse of positions of trust.

Civil and regulatory enforcement

The FCA can pursue civil enforcement under UK MAR without involving the criminal courts. The standard of proof is lower, requiring only the balance of probabilities.

Civil and regulatory penalties include:

• Unlimited financial penalties

• Public censure and reputational damage

• Prohibition from working in regulated financial services

• Disgorgement of profits

• Injunctions preventing future conduct

The FCA may also refer cases to the Crown Prosecution Service for criminal proceedings or pursue both tracks simultaneously.

How is insider trading detected and investigated?

Detecting insider trading presents challenges because offenders naturally try to conceal their activities. However, UK authorities have developed sophisticated methods to identify suspicious conduct.

The FCA operates a dedicated Market Surveillance team that monitors trading patterns across UK markets. Unusual price movements or trading volumes before major announcements trigger automatic alerts for review.

Detection methods include:

• Algorithmic surveillance systems that flag anomalous trading patterns

• Analysis of trading timing relative to corporate announcements

• Cross-referencing trading activity with known insiders and their connections

• Tips from whistleblowers, competitors and market participants

• Information sharing with international regulators

Once suspicious activity is identified, the FCA can compel production of documents, require testimony under oath, obtain court orders to freeze assets and collaborate with law enforcement agencies.

Investigations often trace communication records, including emails, phone calls and messaging apps. Modern forensic techniques can recover deleted messages and establish connections between insiders and traders that might otherwise remain hidden.

The FCA also works closely with overseas regulators. Inside information often crosses borders, and international cooperation is essential for effective enforcement.

Key takeaways for UK investors

Understanding insider trading law protects both you and the integrity of the markets you participate in. Here are the essential points to remember:

• Insider trading occurs when someone trades securities based on material, non-public information.

• Under UK law, the conduct is called insider dealing when prosecuted criminally.

• UK MAR provides the main regulatory framework, enforced by the FCA.

• Inside information must be precise, non-public, price-sensitive and related to securities or issuers.

• Both criminal and civil penalties can apply, including imprisonment, unlimited fines and prohibition orders.

• Detection methods are sophisticated, and international cooperation increases enforcement reach.

• Even unintentional recipients of inside information can face liability if they trade on it.

If you receive information that might be inside information, it is generally prudent not to trade until you have taken appropriate advice. If you are unsure whether information qualifies as inside information, seek legal advice before acting.

Market integrity depends on participants following the rules. By understanding what insider trading is and why it is prohibited, you contribute to fairer, more efficient markets that serve everyone.