The Netherlands' Tax and Customs Administration has scrapped its planned Microsoft 365 public-cloud rollout and will pursue an on-premises, open-source path instead. Roughly 5,000 employees had already migrated to Microsoft 365 before the Dutch Advisory Council on ICT Assessment recommended reversing the rollout in June. The government paused the plan in July, and the new decision replaces the cloud deployment with an approach built around on-premises systems and European open-source software. The administration will keep its existing Microsoft software in place for now rather than immediately swapping it out.
State Secretary for Finance Eelco Eerenberg laid out the timetable in a letter to Parliament. Mail and calendar services are to be delivered on-premises in 2027, followed later that year and into 2028 by European open-source options for personal storage and collaboration. Eerenberg said this would move the government toward a more sustainable and autonomous solution for those functions. The on-premises email and calendar environment will still rely on Microsoft software, including Outlook, while the open-source work covers storage and collaboration.
The ICT assessment concluded the Microsoft 365 public-cloud design fell short on information security, information processing and future-proofing. It also flagged concerns about keeping confidential documents on American servers instead of the government networks previously used. The proposed setup relied on standard Microsoft encryption rather than Double Key Encryption, which would have given the administration more control. The assessment further noted that end-to-end encryption would not have been enabled by default for one-to-one Teams calls and would have been unavailable for group calls under the chosen configuration. Those findings applied to the deployment design, not to every possible Microsoft 365 configuration.
Vendor lock-in, reduced flexibility, digital sovereignty worries and the lack of an adequate exit strategy were also identified as showstoppers. The decision lands amid a broader European push, with the Linux Foundation releasing its 2026 State of Open Source in Europe report at the Open Source Summit Europe. The report found that 94 percent of European Union organizations consider digital sovereignty important, with 61 percent calling it very important. Linux Foundation Europe general manager Thierry Carrez said in a keynote that Europe has heard the message on digital sovereignty.
Linux Foundation board chair Nithya Ruff said onstage at the summit that the need for digital sovereignty is global, citing Sierra Leone, the US and China. The Netherlands is also examining a government-wide shift from Windows and proprietary software to Linux and open-source programs. Switzerland's military and other agencies have announced moves to Linux and openDesk, a German open-source office suite, and Austria, France, Germany and Ireland have also pursued Linux migrations.
Other Dutch government agencies are developing Digitaal Autonome Werkomgeving Overheid, or Digital Autonomous Work Environment for Government, starting with replacing the Windows desktop with the Dutch Linux distribution NixOS. France's La Suite and Germany's openDesk are under consideration for the desktop suite, along with a possible homegrown version of MijnBureau. That self-hosted suite combines Nextcloud for storage and collaboration, Collabora for office documents, Element for messaging and OpenProject for work management. No specific open-source programs or software stacks have been chosen yet for the tax administration.
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