Mathilde Ostertag is a partner in Osborne Clarke's Tax team, based in Luxembourg where she leads the tax practice. Mathilde is an experienced tax lawyer, advising fund managers, financial institutions and private equity investors on the tax and legal aspects of fund structuring, securitisation, structured finance and capital markets transactions. She is recognised in Chambers Europe and ITR World Tax as a leading tax practitioner in Luxembourg.

Key focus areas

  • Structuring and tax advice on investment funds, including private equity, venture capital, real estate and debt funds.
  • Tax structuring of securitisation, structured finance, derivatives and capital markets transactions.
  • SME M&A transactions (including negotiations, due diligences, closing and post-closing reorganisations) 
  • Domestic and international tax planning, corporate reorganisations, carried interest, management incentive plans and ESOPs
  • Tax dispute
  • Compliance.

Who I advise

  • Global fund managers and financial institutions 
  • Asset managers
  • Luxembourg and broad region SME corporates
  • Family offices
  • HNWIs.

Sector focus

  • Financial Services – advising fund managers, financial institutions and investment funds on tax structuring, compliance and transactional matters.
  • Real Estate – structuring tax-efficient real estate investment and asset management vehicles
  • Mobility and Infrastructure – structuring M&A deals across the broad region, including cross-border tax advice.

How I help clients

  • Mathilde takes a practical, business-focused approach to tax structuring, translating complex rules into clear, actionable strategies for clients.
  • She works closely with clients to identify tax and structuring risks early and to design solutions that are commercially workable and compliant.

Notable experience

  • Advising a Luxembourg investment fund on the acquisition and tax structuring of a German hotel real estate asset 
  • Structuring the set up of a Luxembourg investment fund platform focusing on luxury real estate assets and other catering ventures
  • Advising Luxembourg securitisation vehicles on specific crypto (and digital) assets transactions
  • Advising on the multiple acquisitions of Luxembourg operative entities in various fields (mobility, HR services, insurance, etc…)

Credentials and recognition

  • Ranked Band 4, Tax (Luxembourg), Chambers Europe 2025
  • Highly Regarded Practitioner, ITR World Tax 2024–2025
  • Recommended Lawyer in Tax, Legal 500 EMEA 2023–2024
  • Member of the International Fiscal Association (IFA) the International Bar Association (IBA), the Luxembourg Capital Market Association and the ALFI tax committee
  • Board member of the Ladies in Law Luxembourg Association (LILLA) and the WIN (women in network).

Mathilde Ostertag is extremely clever and fights your corner to get tax reports out quickly. When engaged, she is phenomenally clear, user-friendly, gets it instantly and is not afraid of forming views."

Chambers Europe
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