Overview
Thomas advises and litigates on all aspects of revenue law. He regularly appears before the First-tier and Upper Tribunals and has also represented taxpayers (both with and without a leader) in the Administrative Court, Court of Appeal and Supreme Court. Thomas is on the Attorney-General’s A Panel.
He is recommended for corporate and private client/personal tax in Chambers UK Bar and Legal 500 UK Bar as well as for indirect tax in Legal 500.
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Corporate tax
“Very cerebral and has good analytical skills.” “He gets up to speed, and is both responsive and practical in his approach.”
Thomas has represented the Crown in most of the major cases involving partnership taxation in recent years, most recently addressing the Supreme Court on the scope of the miscellaneous income charges in HFFX LLP v HMRC. This case is the culmination of six years litigating these issues, both in that decision and in BlueCrest Capital Management v HMRC [2023] EWCA Civ 148 and Odey Asset Management v HMRC [2021] UKFTT 31, where Thomas has appeared against many of the leading silks of the tax bar: Kevin Prosser KC, Malcolm Gammie KC, David Goldberg KC and Jonathan Peacock KC. The Boston Consulting litigation [2024] UKFTT 84 applies these issues to the post-2014 mixed membership rules.
Thomas has been involved in extensive litigation on corporate taxation. The tax consequences of corporate finance among international groups was at issue in BCM Cayman [2023] EWCA Civ 1179, where a Cayman business borrowed to invest in a UK partnership (at first instance this case also involved major issues of transfer pricing) and in Syngenta Holdings Limited which applied the unallowable purpose restrictions in the context of a major corporate reconstruction. ScottishPower [2025] EWCA Civ 3, on whether the costs of settlement of regulatory proceedings are deductible, will be going to the Supreme Court in the next year.
Thomas acted for the taxpayer in Stirling Jewellers [2020] UKUT UKUT 245, an unusually large quantum of profits dispute where HMRC were asserting that a jewellers had understated its profits by tens of millions of pounds, and where the Tribunal rejected HMRC’s approach of seeking to apply the corporation tax loan to participators charge in any case where they found understated profits: an issue on which Thomas will return to the Upper Tribunal shortly in Cheon Fat [2025] UKUT 287.
Thomas regularly advises on issues concerning partnerships and LLPs, and more generally on corporate restructuring and incentive structures, and the implications of the Transactions in Securities provisions.
Thomas also has extensive experience of Research and Development claims, with a particular focus on software.
Indirect tax
“Excellent sophisticated analysis of difficult niche tax issues. Clear and commercial.’”
Recent work includes:
GC Field & Son v HMRC (2021) – Thomas successfully represented the taxpayer in a case concerning over £1 million in SDLT. While the SDLT planning that the taxpayer had used had been rendered ineffective by retrospective legislation, Thomas showed that HMRC had failed to take action in time to dispute the liability.
A-Dec Dental v HMRC [2017] UKUT 342 – Thomas successfully represented the taxpayer in a case on the customs classification of dental lamps. As with most classification disputes this was highly fact sensitive and depended on exactly how the items were best described: it also concerned the implications of a Commission Implementing Regulation that determined the classification in HMRC’s favour after the time period under appeal: Thomas showed that this should not be applied retrospectively.
Thomas advises extensively on all aspects of SDLT, dealing with both domestic acquisitions (including for example the application of multiple dwellings relief of questions as to the application of the various higher rates) and commercial developments.
He also advises on VAT and customs duties, including questions of export procedures and classification.
Private client and employment
“A good, strategic thinker. Thomas is very bright and on top of the arguments. He thinks quickly on his feet and deals well with curveballs thrown by the judge.”
Thomas advises extensively on private client matters such as the taxation of estates and UK and offshore trusts, including applications to set aside transactions before English courts and overseas jurisdictions, where he provides statements of the UK tax position for foreign courts.
In Bunting v HMRC [2025] UKUT 96, he represented the taxpayer before the FTT and UT concerning capital gains relief for losses on loans to businesses. In MacKay v Wesley [2020] EWHC 3400, appearing alone at first instance and led on appeal by Nicholas le Poidevin KC, he successfully set aside the appointment of the Claimant as trustee—an appointment that had exposed her to significant tax liabilities. This case examined fundamental questions about the nature of trusteeship and how it can be accepted and disclaimed.
Thomas advises on tax issues that arise in divorce proceedings. In Gallagher v Gallagher [2022] EWFC 53, Mostyn J praised his “conscientious and prompt advice” when he provided a joint note to the court at short notice.
Since his involvement in the Rangers EBT litigation at the beginning of his practice, he has developed strong expertise in employment taxation, covering the taxation of benefits, employee trusts, the application of PAYE applications (representing the taxpayer in Giuliani v HMRC [2021] UKFTT), and intermediaries/IR35 litigation. He authors the taxation chapter in Mortimore on Directors.
He regularly advises on pension taxation matters, including loss of protection following mistaken contributions, penalties for inappropriate investments, and unauthorised payment charges. In Bayonet Ventures LLP v HMRC [2018] UKFTT 262, he appeared for the taxpayer in a case examining whether HMRC had assessed the correct person for scheme sanction charges and the extent of LLP transparency for pension purposes.
Public law
Thomas regularly advises on judicial review and legitimate expectation issues that arise in the context of tax.
He appeared unled in the Supreme Court in Whitter [2018] UKSC 31 on the application of proportionality in the Construction Industry Scheme, before the Court of Appeal in Amrolia [2020] EWCA Civ 488, a judicial review of the collection procedures following disputes over partnership losses, and acted for the third claimants in ALR and ors v Chancellor of the Exchequer [2025] EWHC 1467 (Admin), the challenge to the introduction of VAT on school fees.
Directory quotes
The Chambers Guide
Corporate Tax
Rank: Band 1
- “Very cerebral and has good analytical skills. He gets up to speed and is both responsive and practical in his approach.”
- “A highly able junior with a good intellect.”
- “Diligent, responsive and very easy to work with.”
- “He has an encyclopaedic knowledge of the law.”
- “He has an impressive and broad-ranging corporate tax practice, a growing reputation in employment tax matters and experience of cases involving partnership structures.”
Private Client Tax
Rank: Band 3
- “Thomas is very bright. He has an encyclopedic knowledge and is practical in putting it into practice.”
- “Thomas was able to set out our client’s case in a simple but comprehensive manner, ensuring the tribunal understood his submissions and the key points.”
The Legal 500
Tax: VAT
Ranking: Leading Junior, Tier 3
- “Excellent sophisticated analysis of difficult niche tax issues. Clear and commercial.”
- “He is a patient professional who leaves no stones unturned.’”
- “Incredibly sharp, incisive and alive to the commerciality of the tax position for the client.’”
Tax: Corporate
Ranking: Leading Junior, Tier 1
- “Quite simply the best senior junior commercial tax barristers in the market. He has vast experience with high value and complex tax litigation. He is able to almost instantly identify the most important technical points in arguments.”
- ‘”He is a patient professional who leaves no stones unturned.’”
- “He is a patient professional who leaves no stones unturned.’”
- “Incredibly sharp, incisive and alive to the commerciality of the tax position for the client.’”
Tax-Private Client: Personal Tax
Ranking: Leading Junior, Tier 2
- “A good, strategic thinker. Thomas is very bright and on top of the arguments. He thinks quickly on his feet and deals well with curveballs thrown by the judge.”
- “Thomas has a rare talent of expressing complex arguments simply in oral submissions, clear writing and when explaining matters to lay clients.“
- ‘”as a good analytical mind, and is able to work on his own without a QC in the higher courts.’”
- “Immensely bright and very responsive.’”
Chambers High Net Worth
Tax: Private Client
Ranking: Leading Junior, Tier 3
Thomas Chacko advises on high-stakes personal tax cases. He has experience representing HMRC and high net worth clients. Chacko is notable for his expertise in the taxation of partnerships.
- “Thomas is very bright. He has an encyclopedic knowledge and is practical in putting it into practice.”
- “Thomas was able to set out our client’s case in a simple but comprehensive manner, ensuring the tribunal understood his submissions and the key points.”
Appointments
Attorney General’s A Panel.
Memberships
Revenue Bar Association
Publications
Contributor to Mortimer on Company Directors (Third edition)
Contributor to Halsbury’s Laws (Stamp Taxes)
Career & education
Career
2007
Called to the Bar (Inner Temple)
2008-2009
Pupillage, Pump Court Tax Chambers
2009
Tenant, Pump Court Tax Chambers
2011
2 month secondment, HMRC Solicitors Office
2013
3 month secondment, Deloitte
2015
Appointed Junior Counsel to the Crown – “C” panel
2021
Appointed Junior Counsel to the Crown – “B” panel
Education
2007-2008
BCL, St Edmund Hall, Oxford University (Restitution, Personal Taxation, Corporate Taxation, Medieval Law)
Gray’s Inn Tax Chambers prize for Personal Taxation
2006-2007
BVC at ICSL (Very Competent)
Major BVC Scholarship with Duke of Edinburgh’s Entrance Scholarship, Inner Temple
2005-2006
CPE, City University (Distinction)
2000-2003
St John’s College, Cambridge University, BA (Hons)(Natural Sciences)
Master’s Prize
Wright Prize