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Helen Buchanan



Standout performer

Legal 500 2015

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About Helen Buchanan

Helen leads the firm’s tax disputes practice, advising clients on complex UK and international tax disputes across all sectors.

Her contentious caseload spans diverted profits tax, transfer pricing and corporate tax disputes, permanent establishment and controlled foreign company (CFC) issues, employment taxes (including off-payroll working), capital gains and transfer taxes, IPT, VAT and tax fraud.

She has extensive UK and international litigation experience and, as a CEDR-accredited mediator, also has a strong track record of resolving cases out of court.

Alongside her contentious practice, Helen brings a practical and risk focussed approach to a wide range of corporate and finance transactions, including M&A, joint ventures, securitisations, leveraged finance, debt restructurings and corporate reorganisations.

Her sector experience includes energy and natural resources, infrastructure, TMT, pharmaceuticals, hospitality, retail and financial services, and she heads the London office's energy tax practice.

She is ranked in Band 1 for contentious tax by Chambers & Partners.

Recent work

Contentious and Advisory

  • Advising various multinational clients on disputes relating to transfer pricing, valuation, diverted profits tax (DPT), controlled foreign company (CFC) and permanent establishment risk.
  • Advising a UK corporation on employment tax disputes affecting a substantial section of its workforce.
  • Advising multinational groups investing in Africa and Asia on tax disputes relating to capital gains tax, withholding taxes, VAT, branch profits tax and thin capitalisation.
  • Advising on insurance premium tax (IPT) and petroleum revenue tax (PRT) enquiries and disputes.
  • Advising an overseas government on aspects of its tax policy and on the settlement of a material tax dispute.
  • Advising a UK group on a potential tax fraud investigation.
  • Advising various groups on "unallowable purposes" challenges relating to UK financing structures.
  • Advising on international tax and data protection issues involving the digital economy.
  • Advising on tax-related state aid challenges.


  • Advising Ontario Teachers’ Pension Plan on a sale of 30 per cent of its stakes in Bristol and Birmingham airports to Australia’s New South Wales Treasury Corp and investment firm Sunsuper Superannuation Fund.
  • Advising Neptune Energy (backed by funds advised by Carlyle and CVC) on its US$3.9bn acquisition of ENGIE E&P International.
  • Advising CK Hutchison Holdings on its Italian mobile telecoms joint venture with VimpelCom.
  • Advising ArcLight Capital Partners on its acquisition of Total’s 100 per cent operated interest in the Frigg natural gas pipeline and the St Fergus Gas Terminal, and Total’s 67 per cent operated interest in the SIRGES gas pipeline for £585m.
  • Advising Ontario Teachers’ Pension Plan and PSP Investments on their acquisition from Banco Santander of interests in Cubico Sustainable Investments, an international portfolio of renewable energy and water infrastructure assets valued at over $2bn, and their subsequent pro rata acquisitions of Santander’s stake.
  • Advising the Bank of England throughout the financial crisis, including on the special liquidity scheme, discount window facility and other measures.
  • Advising various UK-based groups on convertible and hybrid bond offerings.




Professional qualifications

  • CEDR accredited mediator