Jan van Nass

Jan specialises in complex litigation with a focus on contract law and liability law. He is well versed in matters relating to commercial contracts, M&A transactions and earn-outs, failed negotiations and discovery proceedings. Jan also has particular focus on liability in the corporate sphere, such as auditor liability and director and shareholder liability. He represented clients across various sectors including energy, oil, finance, accountancy and government. Jan has been in practice as an attorney since 2007. Prior to co-founding Ysquare, Jan worked in the commercial litigation departments of Allen & Overy and BarentsKrans for over 8 years, litigating a variety of contentious matters. Subsequently, Jan gained practical experience by working as in-house counsel at KPMG for several years, managing the company’s professional liability cases. He completed the Grotius postgraduate course on National and International Contract Law as well as a postgraduate course on Financial-Economic Criminal Law at the VU University Amsterdam. Jan is admitted to the Dutch Bar and is a member of the Corporate Litigation Association, the Accounting Law Association and the Procedural Law Association.


Post M&A
Litigation for the sellers of an education company regarding an earn-out and alleged warranty breaches

Various disciplinary and civil proceedings regarding the auditors’ professional liability

Litigation for a Dutch oil refinery regarding a contractual dispute with a technology supplier.

Summary arbitral proceedings for a Dutch energy provider regarding a contractual dispute with a strategic supplier

Litigation for the former CEO of a public company regarding directors’ liability in bankruptcy

Litigation for a foreign central bank regarding its alleged liability in respect of the bankruptcy of a Dutch subsidiary bank

Litigation for a public institution regarding a contractual dispute with a union


Since 2019
Ysquare | Attorney

2016 – 2019
KPMG | Attorney (in-house)

2012 – 2016
BarentsKrans | Attorney

2007 – 2012
Allen & Overy LLP | Attorney


VU Amsterdam | Postgraduate in Financial-Economic Criminal Law

Grotius Academy | National and International Contract Law

Leiden University | LL.M.

Université Paul Valéry, Montpellier | Diplôme approfondi de langue française


Case comment on Accountancy Division 6 September 2019, Tijdschrift Tuchtrecht 2020/10 

De accountantsorganisatie en het inzagerecht van art. 843a Rv, MvV 2019/11, pp.  398-405

Case comment on CBB 18 June 2019, JOR 2019/196 (AFM / EY)

Gegevensverstrekking door de accountant op grond van art. 126nd Sv, Sanctierecht & Onderneming 2018, nr 1, pp. 28-32

Case comment on Supreme Court 26 April 2013, JBPR 2013/41 (Bruscom)


Dutch, English, French, German