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United Kingdom
United Kingdom
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CASE STUDY
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Thin capitalisation meaning
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What does Thin capitalisation mean?
Thin capitalisation describes a company funded mainly by debt rather than equity, i.e. a high debt-to-equity ratio (high leverage/gearing), often via shareholder or intra-group loans. A company is thinly capitalised when debt significantly exceeds equity. The expression is descriptive rather than a defined legal term, but it has significant tax and financing implications.
In the UK (England & Wales, Scotland and Northern Ireland), thin capitalisation issues are addressed mainly through transfer pricing rules (requiring arm’s length debt capacity and pricing) and the Corporate Interest Restriction, which can cap deductions for interest. HMRC may adjust or deny deductions, or recharacterise excessive related-party debt where funding is not on arm’s length terms or lacks commercial substance.
In Ireland, there is no statutory definition. Thin capitalisation risk is managed through transfer pricing (Part 35A TCA 1997) and the ATAD Interest Limitation Rules, which restrict interest deductibility by reference to earnings; Irish Revenue focuses on arm’s length funding and debt capacity.
The term is typically used in acquisition finance, group treasury and tax due diligence to flag exposure to restricted deductions, transfer pricing adjustments and penalties. Practically, parties assess capital structure, covenant headroom and document the commercial rationale for debt levels and terms.
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View the related Practice Notes about Thin capitalisation
PRACTICE NOTES
EU tax law collection: principles, VAT, overpaid tax; UK retained/assimilated law post-Brexit; DAC/DAC6; European Q&A country guides
This page brings together Tax resources that deal with EU law matters. For broader guidance on EU law, consult EU structure, EU legislative process, EU judicial system, and EU rights and policies within the EU Law topic in the Public Law practice area. EU principles EU principles and tax—overview VAT—EU legal principles VAT and abuse of rights Overpaid tax—restitution Overpaid tax—interest and damages Interaction of EU law and direct tax [Archived] A history of EU law and CFC regimes [Archived] A history of EU law and thin capitalisation and transfer pricing regimes [Archived]...
21 May
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PRACTICE NOTES
UK transfer pricing for private equity buyouts: arm’s length financing, thin capitalisation, participation rules, HMRC engagement (ATCAs/APAs), self-assessment, and forthcoming reforms in Finance Bill 2026
FORTHCOMING CHANGE relating to UK transfer pricing legislation: Finance Bill 2026 (as introduced) proposes a suite of amendments to the UK’s transfer pricing framework. Once enacted, and applying to accounting periods beginning on or after 1 January 2026, the reforms will, amongst other steps, disapply UK‑to‑UK transfer pricing (with targeted exclusions to prevent tax arbitrage), revise the participation condition, confirm that the OECD Model Tax Convention and OECD Transfer Pricing Guidelines operate as interpretative aids, and update the financial transactions provisions so UK rules more closely align with the OECD Transfer Pricing Guidelines. In parallel, at Budget 2025 the government confirmed it will proceed with an obligation for in‑scope multinationals to report annually on cross‑border related party transactions for accounting periods beginning on or after 1 January 2027. Technical regulations for the new ‘International Controlled Transactions Schedule’ (ICTS) are expected in spring 2026. For further detail on the reforms, see News Analyses: Finance Bill 2026—reform of UK law in relation to transfer pricing, permanent establishment and diverted...
22 May
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PRACTICE NOTES
UK transfer pricing of inter-company debt and financial transactions: loans, guarantees, cash pooling, hedging; OECD Guidelines, BlackRock, thin capitalisation, and Finance Bill 2026 changes
FORTHCOMING CHANGE relating to UK transfer pricing legislation: Finance Bill 2026 (as introduced) sets out a series of reforms to the UK’s transfer pricing regime, encompassing legislative updates across key areas. Effective for accounting periods commencing on or after 1 January 2026, once enacted, the measures will, amongst other outcomes: disapply UK-to-UK transfer pricing (subject to limited exclusions intended to prevent opportunities for tax arbitrage), revise the participation condition, confirm that the OECD Model Tax Convention and the OECD Transfer Pricing Guidelines serve as interpretative aids, and introduce several amendments to the provisions governing financial transactions to better align the UK rules with the OECD Transfer Pricing Guidelines. Alongside this package, the government stated at Budget 2025 that it will proceed with an annual reporting requirement for in-scope multinationals to report information each year on cross-border related party transactions for accounting periods beginning on or after 1 January 2027—the detailed regulations for the new ‘International Controlled Transactions Schedule’ (ICTS) are...
22 May
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