Michael has a chancery practice focused mainly on trust, probate Court of Protection and estate litigation. In addition to that he undertakes a significant volume of professional negligence litigation concerned with tax planning and will drafting and estate administration where he acts for both claimants and defendants. He is also well versed in capital taxation work and regularly advises in relation to inheritance tax, capital gains and SDLT planning and mitigation. He has acted for a number of high profile clients in the entertainment industry and in the aristocracy.
Legal 500"Michael is technically brilliant and delivers an excellent, timely service"
Chamber and Partners UK Bar 2022"Has an innate ability to understand how a case will play out. Michael is extremely user-friendly and condenses complex legal issues into clearly understandable advice. He also has a very detailed knowledge of relevant tax law."
Chambers and Partners UK Bar 2022"Very knowledgeable and his advice is always very easy to comprehend; his opinions are always very sensible and given in a way clients can understand. He is also very quick at dealing with matters and his turnaround time is wonderful."
Chambers and Partners UK Bar 2020"His advice is very timely, succinct and helpful."
Chambers and Partners UK Bar 2020"He's quick, responsive and provides very sensible and pragmatic advice."
Legal 500 2020"Turns work around very quickly, excellent with clients and has an excellent and broad knowledge."
Chambers and Partners High Net Worth 2019"He's incredibly calm and thoughful in his approach, which works incredibly well with clients."
Chambers and Partners High Net Worth 2019"He is so knowledgeable on the knotty trust issues."
Chambers and Partners UK Bar 2019"He really knows his stuff and will fight his client's corner very hard."
Chambers and Partners UK Bar 2019"Deeply experienced and is able to turn around advice very quickly when required so to do."
“He really knows his stuff and will fight his client’s corner very hard.”
“Deeply experienced and is able to turn around advice very quickly when required so to do.”
“A very strong advocate who takes the judge through all the issues in a lucid and concise manner.”
Chambers and Partners UK Bar 2019
‘Extremely efficient.’
Legal 500 2019
“Very knowledgeable and his advice is always very easy to comprehend; his opinions are always very sensible and given in a way clients can understand. He is also very quick at dealing with matters and his turnaround time is wonderful.”
Chambers UK 2018
“Michael is a tenacious and determined advocate.”
Chambers 2018 – Star Individual
“Thoughtful and wise.”
The Legal 500 2017 – Private Client
“Experienced and takes a pragmatic approach.” “Produces quality opinions and drafting with speed and efficiency.”
Chambers UK 2017 – Chancery Traditional
“He is always sensible, realistic and user-friendly.”
Chambers UK 2017 – Court of Protection Property & Affairs
“He has great presence”
He “advises comprehensively, and has a thorough understanding of the issues involved”
“He makes his case well and is a pleasure to deal with”
Chambers UK 2014
“Highly sought after for advice and representation on the spectrum of tax, trusts and estates matters”
“Charismatic” with a “calm and reasoned approach” and a “great sense of humour”.
Clients warm to his “approachable and user-friendly manner”.
Chambers UK 2012
“Thoroughly good from a technical point of view” and “never ruffled in court, knows how to push a case forward”.
Chambers UK
“Approachable and extremely helpful.”
Legal 500 2010
Michael is very experienced in relation to both the contentious and non-contentious aspects of trust law and the administration of estates. He has advised the trustees of several substantial landed estates in relation to trust disputes. He has also advised trustees who are embroiled in divorce litigation affecting trust beneficiaries. He has conducted numerous contentious probate actions and prosecuted and defended many claims under the Inheritance (Provision for Family and Dependants) Act 1975. He has acted in a number of claims under Section 50 of the Administration of Justice Act 1985 (removal of executors) and in claims for breach of trust and the removal of trustees.
Recent matters include As the father of a disabled child he has a special interest in disabled trusts and the taxation thereof and personal injury trusts.
Michael has also been instructed in cases not within the public domain including advising aristocracy in relation to family provision, divorce claims and the administration of dynastic trusts.
Michael has acted in a number of significant Court of Protection cases. He has wide experience of contested statutory will cases and cases involving contested deputyships and attorneyships.
He appeared in Re P [2010] Ch 33 which was the first reported decision of a High Court Judge (Lewison J) on the jurisdiction to make statutory wills under the Mental Capacity Act 2005 and the principles to be applied. He has also appeared in the following cases:
He has also been involved as a mediator in Court of Protection matters acting under a pilot scheme promoted by the Office of the Public Guardian.
He has acted in a number of unreported Court of Protection matters involving multi million pound estates.
A commanding presence – he’s a man of few words but what he says is worth its weight in gold.” “A good advocate with a breadth of experience in this area.”
Chambers UK 2015 – Court of Protection
“He has great presence.” “An excellent barrister with fantastic drafting skills – he always makes time for you.”
Chambers UK 2014 – Court of Protection
“The “charismatic” Michael O’Sullivan “is accomplished and well earns his reputation.” O’Sullivan often acts in high-value Court of Protection matters in which substantial assets are in question, and offers “practical advice at a practical price.”
Chambers UK 2013 – Court of Protection
The “charismatic” Michael O’Sullivan is another top pick for property and affairs applications, and also has more than his share of reported decisions in his favour. He is well liked for his “calm and reasoned approach,” and, moreover, his “great sense of humour” is a treasured asset in what can be a gruelling and sensitive area of practice.
Chambers UK 2012 – Court of Protection
Michael is regularly instructed by major insurers in relation to defence of professional negligence claims involving chancery matters such wills, estate administration and failed inheritance and capital gains tax planning transactions. His knowledge of tax gained from his private client trust practice means that he is au fait with the law of taxation. He has also acted in a number of cases that involved claims against Court of Protection deputies.
He is instructed by one of the country’s largest firms in connection with bank will writing schemes.
He has done numerous application for rectification of wills and has advised on the steps required to cure defects in wills or trust documents.
Recent matters
Acting in the defence of a multi-million pound claim brought against a solicitor and professional attorney in relation to the estate of a substantial land owner which was settled at mediation. The case involved allegations of tax planning negligence and breach of duty while acting as attorney.
Defending a large well-known City firm against a professional complaint that arose out of a deed of variation/tax planning transaction.
Acting for a prominent private client firm in relation to alleged bad drafting of a deed of appointment.
Advising an aristocratic family in relation to a claim against solicitors concerned with a badly-drafted deed of appointment.
Acting for defendant solicitors in a multi-party negligence claim involving failed inheritance tax planning involving FORTRA gilts. The claim was brought in the Isle of Man.
In his first fifteen years of practice Michael did a large volume of real property litigation. As a result of this has a thorough grounding in the law of property and the law of landlord and tenant. He has acted in the High Court, Court of Appeal, County Court and Lands Tribunal in:
In addition he has advised in relation to non-contentious transactions and has drafted leases, mortgages, and option agreements.
Michael has a substantial non-contentious practice involved with inheritance tax and capital gains tax planning related to trusts and estates. In addition he advises on income tax issues related to trusts and estates including pre-owned assets tax. He has also acted in cases involving SDLT and Stamp Duty.
He regularly drafts deeds of variation under Section 142 IHTA and deeds of appointment and trust deeds, wills and other documents concerned with tax planning. He has advised in relation to ta- planning arrangements.
He has advised in relation to the dismantling of past schemes such as double trust schemes.
He has acted for taxpayers against the Revenue in Tribunal proceedings.
He is currently involved in a number of claims against solicitors arising out of failed SDLT saving schemes.
As the father of a disabled child he has a special interest in disabled trusts and the taxation thereof and personal injury trusts.
“He has great presence.” “An excellent barrister with fantastic drafting skills – he always makes time for you.”
Chambers UK 2014 – Court of Protection
“Clients warm to due to his “approachable and user-friendly manner.” As well as being a noted expert on mental capacity issues, he is highly sought after for advice and representation on the spectrum of tax, trusts and estates matters, and related professional negligence cases.”
Chambers UK 2012 – Chancery Traditional
Michael is an accredited mediator and was trained by ADR Chambers. He has a growing mediation practice and has conducted mediations in the following areas
He acted as mediator in a number of Court of Protection mediations under a pilot scheme promoted by the Office of the Public Guardian. Michael’s knowledge of taxation issues enables him to assist parties in seeing angles that their own advisers may have overlooked.
As an advocate Michael has attended countless mediations in the course of his practice.
He is well liked for his “calm and reasoned approach,” and, moreover, his “great sense of humour” is a treasured asset in what can be a gruelling and sensitive area of practice.
Chambers UK 2012 – Court of Protection
In the course of practice Michael has litigated a number of partnership disputes and is well versed in the subject. Many of these cases have involved large agricultural partnerships often where land is held under settlements (including Settled Land Act strict settlements). He has however also acted in relation to more humble businesses such as restaurants.
Recent matters
MA Cantab (Magdalene College Cambridge 1982-85)
Inns of Court Law School 1985-86 called to Bar Lincoln’s Inn July 1986
BCL Oxon (St Catherine’s College Oxford 1986-87)
Hubert Greenland Scholar Lincoln’s Inn
Pupillage 1987-88 (pupil Masters included Charles J and Norris J as they now are)
Accredited Mediator – ADR Chambers
Michael is the author of:
Michael is also a contributing author to the chapters on Purpose Trusts and Protective Trusts in Tolleys Trust Drafting and Precedents.
Michael is the author of Lexis Nexis practice notes on
Michael has written various articles, including:
Michael is the author of:
Michael is also a contributing author to the chapters on Purpose Trusts and Protective Trusts in Tolleys Trust Drafting and Precedents.
Michael is the author of Lexis Nexis practice notes on
Michael has written various articles, including:
ACTAPs newsletter 2005: Professional negligence in relation to tax planning
Click here to view Michael’s Privacy Notice.
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