After training as a business economist in Amsterdam, Jan developed into a very experienced CFO, supplemented with more than 10 years of experience in the interim market at PWC and later Conquaestor. In recent years, Jan was a member of the management of Conquaestor and responsible for the interim activities. He has also worked for many years as an interim manager in both financial and general management roles, including at Unilever Bestfoods and Nevi. In his role as Managing Partner, Jan is ultimately responsible for Mandaat and the first point of contact for all interim questions in the Netherlands.


Established back in 2000, Mandaat has risen to prominence as a leading provider of Interim Management solutions on both a national and international scale. The company's ethos revolves around practicality, personalization, and a steadfast focus on delivering tangible solutions and outcomes. In 2016, Mandaat solidified its global presence by joining forces with WIL Group, an endeavour aimed at fortifying and expanding its international reach. Since 2020 Mandaat is part of JBR, by origin corporate finance practice, which lays an even stronger foundation to support her clients. The company's primary goal is to offer managerial support that empowers clients to achieve successful business implementations.

Aligned with this mission, Mandaat equips its clients with seasoned management professionals, along with coaching and strategic guidance during challenging phases. Moreover, the company offers Flexpats, a unique service where skilled Dutch Interim Managers are deployed to overseas subsidiaries of Netherlands-based enterprises.

Leveraging its robust Dutch network, Mandaat identifies top-tier professionals with specialized functional and industry-specific backgrounds. Mandaat's leadership, including Executive Partner Jan Kalisvaart and associate Diederik van den Biggelaar, possess extensive experience as Interim Managers themselves.

This has created Mandaat’s unique personal approach, where the company seeks to establish what type of specialist the client needs.  Its expertise has led Mandaat to become the recommended firm among banks in Holland to assist with the recovery and restructuring of companies in distress.

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Het Rond 6a,
3701 HS Zeist,
The Netherlands

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+31 (0) 30 699 90 06


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