Private Investigators — Self-Employed Tax Guide

The Accounted Business Team·1 March 2026·7 min read

Working as a self-employed private investigator is one of the more unusual career paths — and the tax side is just as distinctive. From surveillance equipment to long hours sitting in a parked car, the expenses you can claim are quite different from most other sole traders. But the principles are the same: keep good records, claim everything you are entitled to, and pay only the tax you owe.

This guide covers everything self-employed private investigators need to know about tax, expenses, and record-keeping for the 2025/26 tax year.

Registering and Paying Tax

If your self-employed income exceeds £1,000 in a tax year (after the Trading Allowance), you need to register with HMRC as self-employed. You will receive a UTR (Unique Taxpayer Reference) number and must file a Self Assessment tax return annually.

Income Tax Rates 2025/26

Your profits (total income minus allowable expenses) are taxed at:

Personal Allowance: £12,570 tax-free.
Basic rate (20%): Taxable income between £12,571 and £50,270.
Higher rate (40%): Taxable income above £50,270.

National Insurance

Class 2 NI: £3.45 per week (£179.40 per year).
Class 4 NI: 6% on profits between £12,570 and £50,270.

Both are calculated and paid through your Self Assessment return. For more information, see our guide on National Insurance for sole traders.

Allowable Expenses for Private Investigators

Private investigation is an expense-heavy business, and claiming every legitimate cost can make a significant difference to your tax bill. Here is a thorough breakdown.

Travel and Mileage

Travel is likely to be one of your biggest expenses. Surveillance work, client meetings, court appearances, and visiting locations all involve significant mileage. As a PI without a fixed permanent workplace, most of your travel qualifies as business use.

Mileage: 45p per mile for the first 10,000 business miles, then 25p per mile. This covers fuel, insurance, servicing, and wear and tear.
Public transport — train, bus, and taxi fares.
Parking fees — including all-day parking during surveillance operations.
Congestion and ULEZ charges.
Tolls and bridge charges.

Given the nature of the work, your annual mileage could be substantial. Keeping a meticulous mileage log is essential — record the date, start and end locations, case reference (you do not need to name the client), and miles driven for each journey. Our guide to claiming mileage explains the process step by step.

Surveillance Equipment

The tools of your trade are fully deductible business expenses:

Cameras — DSLRs, mirrorless cameras, and compact cameras with long zoom lenses for covert photography.
Video cameras and body-worn cameras.
Telephoto and zoom lenses.
Covert recording equipment (where legal to use).
Night vision equipment and infrared cameras.
Binoculars and spotting scopes.
GPS tracking devices (where their use is lawful — be very careful here, as unauthorised tracking is illegal).
Dash cameras for your vehicle.
Memory cards, batteries, and portable chargers.

Larger equipment purchases can be claimed under the Annual Investment Allowance. Smaller items are deducted in the year of purchase.

Computing and Technology

Laptop or desktop computer used for report writing, research, and case management.
Specialist software — case management systems, database access, background check services, open-source intelligence (OSINT) tools.
Printer and scanner for producing client reports.
External hard drives and cloud storage for securely storing case files and evidence.
Mobile phone (business proportion, or fully deductible if it is a dedicated business phone).
Second phone or SIM for operational use.

Vehicle Costs

If you choose the actual cost method instead of simplified mileage rates, you can claim:

Fuel.
Insurance (including any uplift for business use).
Servicing, repairs, and MOT.
Road tax.
Depreciation (capital allowances on the vehicle).
Breakdown cover.

You would then calculate the business-use percentage based on your mileage records. For most PIs, the simplified mileage method is both easier and often more generous, but it is worth running the numbers both ways. Once you choose a method for a particular vehicle, you must stick with it.

Insurance

Professional indemnity insurance — essential for PI work.
Public liability insurance.
Equipment insurance covering cameras, computing equipment, and surveillance gear.
Data protection insurance — given the sensitive nature of the information you handle.
Business vehicle insurance (if not already covered under actual vehicle costs).

Licensing and Professional Fees

SIA (Security Industry Authority) licence fee — private investigators in the UK are expected to hold an SIA licence for certain activities, and the cost is deductible.
Membership of professional bodies — the Association of British Investigators (ABI), the Institute of Professional Investigators (IPI), or the World Association of Professional Investigators.
DBS check fees.
Data protection registration with the ICO (Information Commissioner's Office) — mandatory if you process personal data.

Office and Working From Home

Much of your non-fieldwork time — report writing, research, invoicing, case preparation — is likely done from home. You can claim:

Simplified flat rate:

£10 per month for 25–50 hours.
£18 per month for 51–100 hours.
£26 per month for 101+ hours.

Or actual costs — a proportion of your rent or mortgage interest, council tax, utilities, and broadband based on business use.

Our work from home expenses guide explains both methods.

Training

CPD courses on surveillance techniques, OSINT, digital forensics, or investigative interviewing.
Legal updates and compliance training.
First aid courses.
Conference and event fees for PI industry events.

Marketing

Website design, hosting, and SEO.
Google Ads and online advertising.
Business cards and printed materials.
Directory listings on professional PI directories.

Other Expenses

Accountancy fees or bookkeeping software — using a tool like Accounted helps you stay on top of your finances without the overhead of a traditional accountant.
Business bank account fees.
Stationery, postage, and printing.
Subsistence on overnight assignments — meals and refreshments during extended surveillance operations where you are away from home overnight.
Clothing — only if it is specialist or protective clothing (for example, high-visibility gear for certain environments). Ordinary clothing, even if you buy it for work, is not deductible.

For a comprehensive checklist, see our complete list of sole trader expenses.

Data Protection and Compliance Costs

As a private investigator, you handle sensitive personal data regularly. Under GDPR and the Data Protection Act 2018, you must register with the Information Commissioner's Office (ICO) and ensure you process data lawfully. The registration fee is a deductible business expense, and any costs associated with GDPR compliance — such as secure file storage, data encryption software, or training — are also claimable.

VAT Considerations

You must register for VAT if your taxable turnover exceeds £90,000 in any 12-month rolling period. Most sole trader PIs operate below this threshold.

If your clients are primarily businesses (solicitors, insurance companies, corporate clients), voluntary VAT registration might be worth considering — they can reclaim the VAT you charge, and you can reclaim VAT on your equipment purchases. If your clients are mostly private individuals, adding 20% VAT to your fees is unlikely to go down well. Our VAT registration threshold guide has more detail.

Record-Keeping Tips

Keep case-related financial records separate from case evidence. Your financial records for HMRC are different from your case files.
Photograph receipts immediately. Penny, the AI bookkeeper in Accounted, makes this simple.
Maintain a detailed mileage log — this is especially important given the high mileage typical in PI work.
Record all income including cash payments. Issue receipts for every payment received.
Retain records for at least five years after the 31 January filing deadline.
Set aside 25–30% of income in a dedicated tax savings account.

Key Deadlines

For the 2025/26 tax year:

5 April 2026: Tax year ends.
31 January 2027: File your Self Assessment return and pay your tax bill.
31 July 2027: Second payment on account (if applicable).

Summing Up

Private investigation is a rewarding career that requires sharp attention to detail — and that same attention should extend to your finances. Claim every legitimate expense, keep thorough records, and plan ahead for your tax bill. The money you save through proper expense management can be reinvested in better equipment, marketing, or simply kept in your pocket where it belongs.

Accounted helps UK sole traders stay on top of their bookkeeping and tax. Start your free 30-day trial at getaccounted.co.uk.

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