Working as an IT contractor in the UK gives you freedom, flexibility and control over your work — but it also comes with responsibilities that full-time employees don’t have to think about, especially when it comes to tax, contractor accounting, IR35 rules, and staying compliant. Whether you’re new to contracting or looking to tighten up your processes, understanding your financial responsibilities can help you avoid surprises and stay confident throughout the year.
Operating as a Limited Company
Most UK IT contractors choose to operate through a limited company because it offers more control and can be more tax efficient (see our related blogs on Ltd Co vs sole trader and the 2025 budget for more info). You’ll be responsible for handling your own invoicing, bookkeeping, VAT, corporation tax and annual accounts. While this might sound like a lot, a good contractor accounting setup can make it straightforward and keep everything organised from day one.
Understanding Inside vs Outside IR35
IR35 is one of the biggest factors affecting contractors. It determines whether you’re treated like an independent business or as an employee for tax purposes. Being clear on your IR35 status is essential for UK IT contractors, especially those working through a limited company.
Outside IR35
This means HMRC recognises you as genuinely self-employed. You have more control over how you work, and you’re not treated like an employee of the client.
If you’re outside IR35, you can:
Pay yourself through salary + dividends
Benefit from tax efficiencies
Claim allowable business expenses
Continue operating through your limited company
Inside IR35
You pay tax and National Insurance similar to an employee
You cannot take income as dividends
The agency or end client may deduct PAYE before paying you
Fewer expenses can be claimed
What Determines Your IR35 Status?
Several factors influence whether a contract is inside or outside IR35. HMRC usually looks at three main areas:
Control – Who decides how, when and where you work? The more control the client has, the more likely the contract is inside IR35.
Substitution – Can you send someone else with equivalent skills in your place? A genuine right of substitution usually indicates an outside IR35 position.
Mutuality of Obligation (MOO) – Is the client obliged to give you continuous work, and are you obliged to accept it? Employees usually have this; independent contractors don’t.
Other supporting factors also matter, such as providing your own equipment, having multiple clients, taking on financial risk and how your contracts are worded. A strong combination of these indicators generally leads toward an outside IR35 assessment.
The IR35 rules only apply if the end client is a public sector organisation or, if they are in the private sector, they are classified as a medium or large company — in which case the onus is upon them to assess whether you are inside IR35. This is a key consideration for contractors working with medium or large private-sector clients.
Why a Good Accountant Makes All the Difference
Being an IT contractor comes with freedom but also responsibility. The right contractor accountant can take the stress out of running your limited company, making sure you stay compliant, manage tax efficiently and navigate IR35 without surprises.
At AJ Business Accounting Ltd, we work closely with our contractor clients all year round. From reviewing contracts and assessing IR35 risk to handling bookkeeping, VAT, payroll and corporation tax, we make sure everything runs smoothly. We also advise on the best way to pay yourself, plan for tax bills and claim what you’re entitled to. With a dedicated point of contact and clear guidance at every step, we help you focus on your work while keeping your finances under control.
Get in touch today to see how we can help you run your contracting business with confidence.
📧 Email: info@aj-financial.co.uk
📞 Phone: 01823 746382
FAQs for IT Contractors
- What is IR35, and why does it matter?
- IR35 determines whether a contract is treated as self-employed or employee-like for tax. It affects how much tax and National Insurance you pay.
- How do I know if my contract is inside or outside IR35?
- It depends on the nature of the end client and the details of your contract: control, substitution, mutuality of obligation, financial risk and integration with the client’s business. Accountants can review your contracts for clarity.
- Do I need a limited company to work as a contractor?
- Not mandatory, but most contractors use a limited company to manage income via salary and dividends. The IR35 assessment “sees through” the Ltd structure, but working as a Ltd Co provides clients with protection against employment status claims — and this is often required.
- Can accountants help me year-round?
- Yes. We handle bookkeeping, VAT, payroll, corporation tax and IR35 guidance, keeping your accounts compliant and stress-free.
- What expenses can I claim?
- Expenses must be for business purposes only (e.g., software, equipment, work travel and professional subscriptions).
