How to Hire a Private Investigator in the UK: A Real Guide

Most people who call a private investigator have never done it before and hope they'll never need to again. That's normal. It usually means a marriage is falling apart, a business partner is behaving oddly, a tenant has vanished owing rent, or a solicitor has told them they need evidence that stands up in court. This guide sets out what actually happens once you pick up the phone, what's legal, what things cost, and how to tell a competent investigator from someone who'll waste your money and possibly land you in legal trouble.

Is hiring a private investigator legal in the UK?

Yes, and it's more common than people assume, solicitors, insurers, HR departments and ordinary members of the public do it every week. There is no requirement for a private investigator to hold a licence in the UK. The Private Security Industry Act 2001 technically allows for licensing of investigators, but that part of the Act has never been brought into force, so anyone can call themselves a PI without formal accreditation. That's not a loophole worth exploiting as a client, it means the burden of vetting falls entirely on you.

What is regulated is what an investigator does with information. Any competent firm should be registered with the Information Commissioner's Office (ICO) as a data controller, and their conduct is governed by UK GDPR and the Data Protection Act 2018. Surveillance work must be proportionate and not amount to harassment under the Protection from Harassment Act 1997. Accessing someone's computer, phone or email accounts without authorisation breaches the Computer Misuse Act 1990, no matter who's paying for it or why. A properly run agency works within these boundaries as a matter of course, not because a client asked them to.

What a legitimate investigator will and won't do

A good investigator will tell you early on what's realistic and what isn't. That's usually the first sign you're dealing with someone reputable rather than someone who'll take your money and tell you what you want to hear.

They will:

• Gather evidence through lawful, overt or covert observation in public or otherwise legally accessible spaces
• Conduct open-source and records-based research, background checks, company searches, land registry checks, court records
• Advise you honestly on whether your case is worth pursuing before taking a deposit
• Provide a written report suitable for solicitors, HR proceedings or family court

They won't:

• Hack email, social media or phone accounts
• Trespass on private property to get a shot or a listening position
• Tap phone lines (this is a criminal offence under the Investigatory Powers Act 2016 for anyone outside the specific authorised bodies)
• Guarantee a particular outcome, such as proving infidelity or securing a conviction

Any investigator promising to hack an account, access phone records, or "guarantee" catching someone out should be shown the door. Beyond the ethics, evidence obtained illegally is usually inadmissible and can expose you, the client, to civil or criminal liability.

Common reasons people hire a PI

Infidelity and relationship concerns still make up a large share of enquiries, but the range is wider than most people expect:

• Family and matrimonial matters, confirming suspicions before or during divorce proceedings, checking on a former partner's living arrangements where it affects child arrangements
• Business disputes, employee misconduct, suspected moonlighting during sick leave, IP theft, due diligence on a potential business partner
• Tracing, finding a missing debtor, a beneficiary under a will, or someone who's disappeared owing money
• Corporate security, bug sweeping offices before board meetings, checking vehicles or premises for tracking devices
• Pre-employment and vetting checks, verifying qualifications, employment history and directorships before a senior hire
• Legal support, serving court documents where a defendant is avoiding service, or locating witnesses
• Fraud and insurance matters, surveillance to establish whether a claimant's stated injuries match their actual activity

For most of these, the investigator's job is to produce something a solicitor, court, employer or insurer can rely on, not simply to satisfy your curiosity. That distinction matters when you're briefing them.

What to check before you instruct anyone

There's no licensing body to check against, so you have to do the vetting yourself. Spend twenty minutes on this before you pay anyone a deposit.

• ICO registration, ask for their registration number and check it on the ICO's public register
• Professional indemnity and public liability insurance, a serious agency carries both, typically £1 million or more of cover
• Membership of a trade body, the Association of British Investigators (ABI) and the World Association of Detectives both have entry requirements and codes of conduct
• A proper contract, you should receive a written engagement letter setting out scope, cost, timescale and what happens if the evidence doesn't support your position
• A landline, a business address and a VAT number if applicable, a firm operating only from a mobile number and a Gmail address is a warning sign
• Willingness to say no, if every case sounds like a sure thing before they've asked you a single question, be suspicious

A firm operating nationally, with staff and associates who know local areas, whether that's London, Manchester, Birmingham or Glasgow, will usually be better placed to deploy quickly and blend in than someone working alone in an unfamiliar town. Surveillance in a city you don't know well is much harder to do without being noticed.

What it actually costs

Rates vary by region, complexity and urgency, but as a rough guide across the UK in 2024:

• Background checks and due diligence: £75, £250 depending on depth
• Surveillance: typically £40, £75 per hour for a single operative, often sold as day rates of £300, £600; two-operative jobs (common for mobile surveillance) cost more
• Process serving: £60, £150 for standard service, more for evasive defendants or urgent deadlines
• Polygraph testing: £300, £600 per test, usually including a written report, see polygraph testing for how this works and its limits
• Bug and camera sweeps: £200, £500 for a domestic property, considerably more for offices or vehicles
• Asset tracing: highly variable, a straightforward company search might be £150, whilst a full international asset trace for a civil recovery case can run into several thousand pounds

Be wary of anyone quoting a flat fee for an open-ended job like ongoing surveillance without a cap or a review point. A reputable investigator will agree an initial block of hours, report back, and let you decide whether to continue rather than running up costs indefinitely.

How the process works in practice

Most cases follow a similar shape.

1. Initial consultation. A phone or video call, usually free, where you explain what's happening and the investigator assesses whether it's something they can help with. Be as specific as you can about dates, names, vehicles and locations, vague briefs lead to wasted hours.

2. Scoping and quote. You'll get a written proposal setting out what will be done, over what period, and at what cost. This is the point to ask about reporting format, especially if the evidence needs to go to a solicitor or a court.

3. Engagement and deposit. Most firms take a deposit or the first block of hours upfront, with the balance on delivery or at agreed intervals for longer jobs.

4. The work itself. For surveillance, this might mean a single day watching a workplace, or several days of mobile surveillance following a vehicle across counties. For tracing or background work, it's usually desk-based and faster, often a matter of days rather than weeks.

5. Reporting. You should receive a clear, dated, factual report, times, locations, descriptions, photographs or video where lawfully obtained. If the case is heading to family court or an employment tribunal, ask in advance what format the receiving party expects; a good investigator will already know.

6. Next steps. A decent firm will tell you honestly whether further work is likely to add anything, rather than suggesting you keep paying for more of the same.

A note on privacy and proportionality

Courts and tribunals take a dim view of surveillance that goes beyond what was necessary to establish the facts. Filming someone in their own garden through a hedge is very different from photographing them meeting someone in a public car park. If your case might end up before a judge, ask your investigator how they'll keep the evidence proportionate, it protects you as much as the person being watched.

Choosing a national firm versus a sole operator

A sole trader working from home can be perfectly competent, particularly for desk-based work like background checks or tracing. Where it gets harder is surveillance and process serving in areas they don't know, or cases needing more than one person at once, a target who splits from a vehicle on foot, for instance, needs two operatives, not one. Firms with coverage across cities such as Leeds, Bristol and Sheffield can put a team together at short notice rather than one person driving three hours to get there.

Getting started

If you're weighing up whether to hire a private investigator, the sensible first step is a conversation, not a contract. Explain what's happened, what you need to achieve, and let an experienced investigator tell you honestly whether it's achievable and what it's likely to cost. LocalPI works across the UK on exactly these cases, get in touch for a straightforward, no-obligation assessment of yours.