Working as a locum doctor in the UK brings unique tax challenges that permanent NHS staff never face. This locum doctor tax complete guide covers everything from IR35 compliance to expense claims, helping you navigate the complex tax rules that apply to medical professionals working on a contract basis.

Whether you're a newly qualified doctor considering locum work or an experienced locum looking to optimise your tax position, understanding these rules is essential for both compliance and maximising your take-home pay.

Understanding IR35 for Locum Doctors

IR35 is the single most important tax rule affecting locum doctors. These off-payroll working rules determine whether you're treated as an employee or genuine contractor for tax purposes.

If you're caught by IR35, you pay tax and National Insurance as if you were an employee, but without employment rights like sick pay or pension contributions. If you're outside IR35, you can use your limited company to potentially reduce your tax burden.

IR35 Determination Process

Since April 2021, large organisations (including most NHS trusts) must make the IR35 determination themselves. However, smaller GP practices typically leave this decision to you as the contractor.

The key factors NHS organisations consider include:

  • Control over how, when, and where you work
  • Whether you can send a substitute
  • Financial risk and opportunity for profit
  • Whether you're integrated into the organisation
  • Provision of equipment and premises

Most NHS locum roles are likely to be inside IR35 due to the controlled nature of medical work and integration requirements. GP practice locum work may offer more flexibility to be outside IR35.

Employment Structures for Locum Doctors

Locum doctors typically work through one of three structures, each with different tax implications.

Direct Employment (Bank/Agency Staff)

When working through NHS staff banks or recruitment agencies as an employee, tax is straightforward. The bank or agency operates PAYE, deducting income tax and National Insurance from your gross pay.

You receive a P60 at year-end and can claim limited expenses through your self-assessment return. However, you miss out on the potential tax benefits of contracting.

Sole Trader/Self-Employment

Some locum doctors work as sole traders, invoicing clients directly. This structure works for those genuinely outside IR35, but carries unlimited personal liability.

You pay income tax and Class 2/Class 4 National Insurance on profits, with Class 4 NI capped at £4,189 for 2025/26. The simplicity makes this attractive for lower-earning locums or those just starting out.

Limited Company Structure

Most established locum doctors use a limited company (personal service company) for contracting. This offers the greatest tax efficiency when outside IR35, but requires more administration.

You take a small salary (typically £12,570 to maximise NI efficiency) and extract remaining profits as dividends. This can save significant tax compared to employment, particularly for higher earners.

Expense Claims for Locum Doctors

Locum doctors can claim various professional expenses, but the rules vary depending on your working structure and IR35 status.

Allowable Expenses

Common expenses you can typically claim include:

  • GMC annual retention fee and specialist registration
  • Professional indemnity insurance (MDU, MPS, MDDUS)
  • BMA membership fees
  • Continuing Professional Development costs
  • Professional journals and subscriptions
  • Travel between different workplaces (not home to work)
  • Professional equipment and instruments
  • Accountancy fees

Travel Expenses

Travel rules are complex for locum doctors. You cannot claim home-to-work travel for regular workplaces, but can claim:

  • Travel between different client sites on the same day
  • Additional travel costs when working at temporary workplaces
  • Travel to training courses and professional meetings

Keep detailed mileage logs and retain all receipts. The current HMRC mileage rate is 45p per mile for the first 10,000 business miles.

Home Office Expenses

If you use your home for business purposes (admin, CPD, client calls), you can claim a proportion of running costs. HMRC's simplified method allows £6 per week for up to 25 hours' use, or £18 per week for 51+ hours.

Tax Planning Strategies

Effective tax planning can significantly impact your net income as a locum doctor. Here are key strategies to consider.

Pension Contributions

Pension contributions remain one of the most effective ways to reduce your tax bill. You can contribute up to 100% of relevant earnings or £60,000 annually (2025/26), whichever is lower.

Locum doctors often miss out on NHS pension benefits, making personal pension planning even more critical. Consider whether to maintain voluntary NHS pension contributions or invest in private arrangements.

Timing of Income

If using a limited company, you have flexibility over when to extract profits. Consider:

  • Deferring dividends to manage tax brackets
  • Accelerating income before tax rate changes
  • Spreading income across family members (where appropriate)
  • Using dividend allowances efficiently

Expense Timing

Time allowable expenses to maximise tax relief. For example, pay annual subscriptions and equipment purchases before your accounting year-end to claim relief in the current year.

Record Keeping Requirements

Proper record keeping is essential for locum doctors, both for tax compliance and to support expense claims.

Essential Records to Maintain

  • All invoices and contracts
  • Bank statements and payment records
  • Expense receipts and documentation
  • Mileage logs with business journey details
  • Professional qualification certificates
  • Insurance documents

Digital Record Keeping

From April 2026, Making Tax Digital rules will likely extend to more businesses. Start using cloud-based accounting software now to stay ahead of requirements and simplify your bookkeeping.

Popular options for medical professionals include Xero, QuickBooks, and FreeAgent. These integrate with banking and can automatically categorise common medical expenses.

Self-Assessment for Locum Doctors

Most locum doctors must complete annual self-assessment returns, regardless of their working structure.

Key Deadlines

  • 31 October: Paper return deadline
  • 31 January: Online return and balance payment deadline
  • 31 July: Second payment on account due (if applicable)

Common Mistakes to Avoid

Typical errors we see in locum doctor returns include:

  • Incorrect IR35 treatment
  • Missing expense claims
  • Incorrect travel expense calculations
  • Failing to report all income sources
  • Inadequate record keeping

Getting Professional Help

The complexity of locum doctor taxation often justifies professional assistance. A specialist medical accountant can help you:

  • Structure your affairs tax-efficiently
  • Navigate IR35 determinations
  • Maximise allowable expense claims
  • Plan for major purchases or career changes
  • Handle HMRC enquiries if they arise

This locum doctor tax complete guide covers the essentials, but every locum's situation is unique. Consider seeking advice from accountants who specialise in working with medical professionals and understand the specific challenges you face.

For personalised guidance on your locum doctor tax situation, speak to our specialist medical accountants who work exclusively with UK healthcare professionals.