Related Party Transactions: Document Transfer Pricing to Beat HMRC

Who This Affects

Transfer pricing rules apply when two connected parties — such as a UK company and its overseas parent, a director lending money to their own company, or two businesses under common ownership — trade with each other. HMRC requires that the price charged in those transactions matches what two genuinely independent parties would agree. This is known as the arm's length principle.

While the formal transfer pricing legislation under TIOPA 2010 Part 4 historically targeted large multinationals, the rules have been extended and HMRC's scrutiny of smaller groups has increased significantly. If your limited company has any transactions with connected parties — even informally structured ones — you need robust documentation.

Common Related Party Transactions to Watch

• Director loans: Money lent to or from the company by a director or shareholder.
• Inter-company loans: Loans between two companies under common ownership, especially cross-border ones.
• Management charges: One group company charging another for services such as finance, HR, or IT.
• Royalties and IP licences: One entity licensing intellectual property to a related business.
• Property transactions: Selling or leasing premises between connected companies at non-market rates.

What HMRC Expects You to Document

HMRC's guidance aligns with the OECD Transfer Pricing Guidelines. For each related party transaction, your documentation should clearly establish:

• The nature and purpose of the transaction — what service or asset is being exchanged and why.
• How the price was determined — which pricing method you used and why it is appropriate.
• Comparable market evidence — data showing that your price reflects what unconnected parties would pay.
• The legal basis — a written agreement signed before or at the point the transaction commences.
• Financial flows — actual invoices, bank transfers, and accounting entries that match the agreed terms.

Documentation should be prepared contemporaneously — not reconstructed after HMRC opens an enquiry. If you cannot show your working at the time the transaction occurred, HMRC can and will substitute its own arm's length price, which almost always results in a higher tax bill plus interest and penalties.

Choosing the Right Pricing Method

The most commonly used methods for UK businesses are:

• Comparable Uncontrolled Price (CUP): Benchmarking your price against equivalent transactions between independent parties. Ideal for straightforward loans or standard services.
• Cost Plus: Charging an appropriate mark-up on the actual cost of providing a service. Often used for management charges.
• Transactional Net Margin Method (TNMM): Comparing net profit margins against comparable independent businesses. Useful where direct comparables are hard to find.

For director loans specifically, the interest rate must reflect a commercial rate. HMRC publishes the official rate of interest each tax year, but this is a minimum benchmark — a commercially motivated lender might charge more depending on the risk profile of the borrower.

Practical Steps to Take Now

• List every transaction between your company and any connected party, no matter how routine it seems.
• Obtain or create a written agreement for each one before the next accounting period starts.
• Run a benchmarking exercise using publicly available databases such as Bureau van Dijk's Orbis, or engage a transfer pricing specialist for higher-value transactions.
• Review your management charge methodology annually and update it if the scope of services changes.
• Keep a dedicated transfer pricing file with all supporting documentation, updated each year alongside your year-end accounts.

Penalties for Getting It Wrong

If HMRC successfully challenges a related party transaction, it can adjust the taxable profits of both parties and charge corporation tax on the restated amount. Penalties for careless errors run up to 30% of the unpaid tax, rising to 100% or more where HMRC considers the behaviour deliberate. The reputational cost of a formal enquiry adds further risk.

Getting your transfer pricing documentation in order is not just about compliance — it is one of the clearest signals to HMRC that your company is well-governed and commercially disciplined. Start with a simple connected-party transaction log and build from there.