Iain was called to the Bar in 2006 and his practice focuses on contentious tax, fraud and investigations.  He has litigated several of the leading cases on HMRC investigative powers, VAT fraud, and the Knowledge/Means of Knowledge tests.

Iain manages a wide variety of work for an international client base, ranging from UHNWIs to PLCs and owner-managed businesses to trusts and funds.  He is often sought out by other legal and professional advisors for a second opinion and to help ‘unlock’ long-running or complex disputes.

Before pupillage, Iain worked for HMRC Solicitor’s Office in both Excise litigation and VAT litigation. He has acted as counsel both for and against HMRC in a variety of disputes in the Tax Tribunal, Upper Tax Tribunal, High Court (Admin, ChD and Comm), Court of Appeal (Civil), House of Lords and UK Supreme Court.  He became a partner at JHA in 2021 and prior to that had been a tenant at a leading set of Chambers and a Dispute Resolution Partner at a City law firm.


Called to the Bar of England & Wales, March 2006


‘Iain MacWhannell – charming and forensically bright. He has fantastic judgment and instinctively knows the right decisions to make in complex, high value commercial litigation. As a former barrister, Iain’s tactics are at the heart of what he does and why he is so very much in demand. Revered for his knowledge and experience of FS, tax, civil fraud and injunctions work, he has a proven track record in heavy weight litigation.’ (Legal 500, 2020)

‘Iain MacWhannell is excellent. He has a keen eye for detail and is an excellent negotiator and litigator. Clients are in the safest of hands with Iain.’ (Legal 500, 2020)


London solicitors & barristers specialising in tax litigation, HMRC tax disputes, HMRC tax appeal, HMRC tax tribunal and HMRC tax penalty appeal.

VATA 1994 s.47, Agency, Onward Supply Relief, & Double Taxation

On 12 July 2021, the First-tier Tribunal (Tax Chamber) (“FTT”) released its decision in Scanwell Logistics (UK) Limited v HMRC [2021] UKFTT 261 (TC), rejecting the taxpayer’s claim for onward supply relief (“OSR”).

Whilst OSR is now limited, post-Brexit, to goods imported into Northern Ireland for onward supply to the EU, the FTT’s discussion of agency under section 47 of the Value Added Tax Act 1994 (“VATA”) is of broader interest.

The case serves as a reminder of the significant financial consequences that can result from errors in tax planning, as Scanwell was ultimately held liable for £5.7 million in unpaid import VAT despite the fact that the imported goods almost immediately left the UK (which, if properly planned, could have meant Scanwell was relieved from liability to import VAT).

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London solicitors & barristers specialising in tax litigation, HMRC tax disputes, HMRC tax appeal, HMRC tax tribunal and HMRC tax penalty appeal.

Raising the bar: UK Supreme Court clarifies the requirements for HMRC to issue Follower Notices

On 2 July 2021, the Supreme Court delivered its judgment in R (on the application of Haworth) v HMRC [2021] UKSC 25, finding unanimously in favour of the taxpayer and upholding the Court of Appeal’s decision to quash the follower notice issued to him.

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London Barristers & Attorneys specialising in Tax Litigation