The short answer
Judicial review is the process by which the High Court supervises the lawfulness of decisions made by public bodies in England and Wales. It is not an appeal. The court asks whether a decision was made lawfully, fairly and within the powers Parliament granted, and it will not substitute its own view for the authority’s. Claims must be brought promptly and in most cases within three months, and they need the court’s permission to proceed.
What is judicial review?
Judicial review is a challenge to the lawfulness of a decision, not to its wisdom. That single distinction explains most of what follows.
It applies where a public body exercises a public function and its decision is said to be unlawful, and it is generally available only where there is no adequate alternative remedy such as a statutory right of appeal. The jurisdiction reaches government departments, local authorities, regulators, immigration decision-makers and, in the right case, public appointment processes. What matters is not who made the decision but whether the function is public.
The court’s role is supervisory. It can tell an authority to think again, lawfully. It cannot tell it what to think.
A claimant who simply disagrees with a decision has no claim, however strongly they disagree. The question is always legality, never merit.
How long do you have to bring a claim?
Promptly, and in most cases within three months of the decision being challenged. Promptness is a separate requirement, so a claim can fail for delay even when it is technically in time.
Several areas run to shorter clocks, and missing them is the most common way a good claim dies before it starts.
| Type of claim | Time limit |
|---|---|
| General judicial review | Promptly, and in any event within three months |
| Planning challenges | Generally six weeks |
| Public procurement | Shorter still, under specialist rules |
| Immigration | Specialist procedural rules, often urgent |
Before proceedings are issued, a claimant will ordinarily send a pre-action letter setting out the decision challenged, the grounds and the remedy sought. It is not a formality. It gives the public body a chance to reconsider, and a reconsidered decision is cheaper than a won one.
Why do most judicial review claims fail?
Most fail at permission. The court asks whether the claim is arguable with a realistic prospect of success, and a large proportion never get past that filter.
But there is a second filter that practitioners consistently underestimate, and it is statutory.
Section 84 of the Criminal Justice and Courts Act 2015 inserted subsections (2A) to (2C) and (3C) to (3F) into section 31 of the Senior Courts Act 1981. The effect is straightforward and severe. At permission stage, section 31(3D) requires the court to refuse permission where it appears highly likely the outcome for the applicant would not have been substantially different had the conduct complained of not occurred. At relief stage, section 31(2A) requires the court to refuse a remedy on the same test.
Three things follow. The court must consider the question if the defendant asks, and may raise it itself, so defendants plead it as a matter of routine. It is a duty rather than a discretion. And the only way out is section 31(2B) or (3E), where the court considers it appropriate for reasons of exceptional public interest, which it must then certify.
The practical consequence is uncomfortable: an authority can act unlawfully and the claimant can still walk away with nothing. The courts do police the limits, though. In R (Hippolyte) v Secretary of State for the Home Department [2025] EWCA Civ 1493, the Court of Appeal overturned an Administrative Court refusal of relief under section 31(2A), reported as the first appellate reversal of its kind.
What are the grounds for judicial review?
There are four principal grounds: illegality, procedural unfairness, irrationality and, where Convention rights are engaged, disproportionality. Frustration of a legitimate expectation runs across them as a further route.
Illegality: acting outside your powers
Illegality arises where an authority exceeds its legal powers, misreads legislation, or acts outside constitutional limits.
R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5. The Government sought to trigger Article 50 by prerogative power, without Parliament. The Supreme Court said no: leaving the EU would strip out rights created by the European Communities Act 1972, and only Parliament could authorise that. Judicial review can restrain the executive where constitutional principle is engaged. Judgment.
R (Bancoult) v Secretary of State for Foreign and Commonwealth Affairs (No 2) [2008] UKHL 61. The Chagos Islanders challenged Orders in Council preventing their return home. The House of Lords upheld the Orders by a majority as within lawful authority. The counterweight to Miller: courts uphold executive action taken within legal limits. Judgment.
Procedural unfairness: not being heard
Authorities must act fairly and observe natural justice.
Ridge v Baldwin [1964] AC 40. A Chief Constable was dismissed without a proper chance to answer the allegations. The House of Lords quashed the decision. Sixty years on it remains the starting point: seniority does not exempt a decision-maker from fair procedure. Judgment.
R (Begum) v Headteacher and Governors of Denbigh High School [2006] UKHL 15. A pupil challenged her school’s refusal to permit a particular form of religious dress. The claim failed. The school had considered the question carefully, followed its policy and acted within its discretion. Fairness is the standard, not perfection. Judgment.
Irrationality: a very high bar
A decision may be unlawful if no reasonable authority could have reached it. Claimants reach for this ground often and clear it rarely.
R (Association of British Civilian Internees: Far East Region) v Secretary of State for Defence [2003] EWCA Civ 473. A compensation scheme was challenged for excluding certain categories. The Court of Appeal refused to interfere: spending decisions are not irrational merely because they are controversial. Judgment.
Legitimate expectation: when a promise binds
Where a public body has given a clear and unambiguous assurance, frustrating it can be unlawful as an abuse of power.
R v North and East Devon Health Authority, ex parte Coughlan [2001] QB 213. A severely disabled claimant was promised a home for life in a care facility. The authority later decided to close it. The Court of Appeal held the decision unlawful, treating frustration of a substantive legitimate expectation as an abuse of power rather than applying the ordinary irrationality test. It is the case to cite when a client relied on something specific they were told. Judgment.
Proportionality: where human rights are engaged
Where Human Rights Act 1998 rights are in play, the court assesses whether the interference is proportionate.
R (Daly) v Secretary of State for the Home Department [2001] UKHL 26. Prison officers examined legally privileged correspondence in prisoners’ absence. The House of Lords held the policy went further than necessary. Structured balancing, not deference. Judgment.
R (SC) v Secretary of State for Work and Pensions [2021] UKSC 26. The two-child limit on benefits was challenged as discriminatory. The claim failed: the policy pursued legitimate aims within Parliament’s margin of discretion. Courts respect parliamentary choices on socio-economic questions unless clearly unlawful. Judgment.
What can the court actually order?
A quashing order, a mandatory order, a prohibiting order, a declaration or interim relief. The court does not remake the decision; it requires the authority to reconsider lawfully.
Since 2022 a quashing order does not necessarily mean what it used to. Section 1 of the Judicial Review and Courts Act 2022 inserted section 29A into the Senior Courts Act 1981, giving the court two further options. It may suspend the quashing until a specified date, during which the impugned act stands, subject to any conditions imposed. It may also remove or limit the retrospective effect, so past actions taken under an unlawful measure survive while the defect is fixed going forward.
Winning no longer necessarily means the decision is treated as never having been made. That changes what a successful claim is worth, and it should shape advice before the first letter goes out.
Do Cart judicial reviews still exist?
No. Section 2 of the Judicial Review and Courts Act 2022 removed the Administrative Court’s Cart jurisdiction with effect from 14 July 2022.
Cart reviews allowed certain Upper Tribunal refusals of permission to appeal to be judicially reviewed. The practical impact falls hardest on immigration and asylum cases originating in the tribunal system, and it is a genuine trap for anyone working from older textbooks or case summaries: the route is described in a great deal of still-circulating material, and it is gone.
Judicial review otherwise remains significant in immigration, particularly where no statutory appeal exists. In R (Medical Justice) v Secretary of State for the Home Department [2010] EWHC 1925 (Admin), the High Court struck down a Home Office policy permitting removal without notice for want of adequate safeguards. Judgment.
What does it cost to bring a claim?
Enough that funding should be settled before proceedings are issued, not after. Costs generally follow the event, and refusal of permission can still leave a claimant paying the other side.
Costs protection exists but has narrowed, and the vocabulary has moved on. Protective costs orders, developed at common law, were placed on a statutory footing as judicial review costs capping orders by the Criminal Justice and Courts Act 2015, on restrictive conditions. Separate and more generous protection applies to environmental claims within the scope of the Aarhus Convention. Anyone advising from older guidance about protective costs orders should check the current position first.
Judicial review: frequently asked questions
What is judicial review in simple terms?
The High Court checking whether a public body acted lawfully, fairly and within its powers. It is not an appeal, and the court will not replace the decision with its own view of what would have been better.
What is the time limit for judicial review?
Promptly, and in most cases within three months of the decision. Promptness is a separate requirement, so a claim can fail for delay even inside three months. Planning challenges generally run to six weeks and procurement claims to shorter periods again.
What are the four grounds for judicial review?
Illegality, procedural unfairness, irrationality and, where Convention rights are engaged, disproportionality. Frustration of a legitimate expectation is a further route, treated as an abuse of power.
Can you appeal a decision through judicial review?
No. Judicial review is supervisory, not appellate. It examines how and under what powers a decision was made, not whether it was the right decision, and it is generally unavailable where a statutory right of appeal exists.
What happens if the outcome would have been the same anyway?
The court must refuse permission or relief. Section 31(3D) and (2A) of the Senior Courts Act 1981 require refusal where it is highly likely the outcome for the applicant would not have been substantially different, unless the court certifies exceptional public interest under section 31(2B) or (3E).
Can a court quash a decision without unwinding the past?
Yes, since 2022. Section 29A of the Senior Courts Act 1981 allows a quashing order to be suspended until a specified date, or to have its retrospective effect removed or limited.
The practical takeaway
Judicial review is powerful but never automatic. It turns on clear unlawfulness, timely action and disciplined argument, and two statutory filters now sit between a genuine grievance and a remedy: permission, and the requirement to refuse relief where the outcome would not have been substantially different.
Assess both before the pre-action letter goes out, alongside costs exposure and one further question the 2022 reforms have made unavoidable. If you win, and the court suspends the quashing or strips its retrospective effect, does your client actually get what they came for.