Dutch Tax Administration drops its move to Microsoft 365
The Belastingdienst, Customs and Benefits now choose their own servers and European open source for email, files and collaboration, from 2027.
The Dutch Tax and Customs Administration (Belastingdienst), Customs (Douane) and the Benefits Agency (Toeslagen) will not move their office software to Microsoft 365 after all. In a letter to the House of Representatives of 5 October 2026, State Secretary for Finance Eelco Eerenberg wrote that the three organisations now choose an on-premises solution combined with open source: the software runs on servers of the Belastingdienst or servers it controls.
From Microsoft 365 to its own servers
- October 2025: the government informed parliament that the Belastingdienst, Toeslagen and Douane would move their office automation to Microsoft 365.
- 11 June 2026: the State Secretary made digital autonomy a priority for the Belastingdienst, with more data centre capacity of its own and a further push on open source.
- 9 July 2026: after critical advice from the Advisory Council on ICT Assessment (AcICT), which concluded that the current approach would not lead to a suitable working environment, the Microsoft 365 programme was paused and the on-premises scenario was to be worked out again.
- 5 October 2026: the choice for on-premises and open source. The State Secretary says this is now possible partly because the Belastingdienst has managed to increase its data centre capacity.
The plan
- 2027: email and calendar first, on-premises.
- Later in 2027 and in 2028: European open source solutions for personal storage and collaboration.
- The approach follows the AcICT advice not to start from one solution from one supplier, but to look at alternatives for each function. Existing licences are reused where possible to limit extra investment.
The letter is open about the cost of the change: some planned tools for records management were part of the Microsoft 365 package and are not available on-premises. The Belastingdienst is working out what is needed, and the State Secretary will report on it in the next progress letter at the latest.
Why it matters
Here a large national administration chooses, function by function, where its email, files and collaboration run. Choosing per function only works when documents move freely between tools, so open, standard file formats matter as much as where the servers are.
Sources
- Tweede Kamer: Toekomstbestendigheid Belastingdienst, letter of the State Secretary for Finance (5 October 2026)
- Kamerstuk 31066 nr. 1550: response to the AcICT advice on the M365 rollout (9 July 2026)
- Rijksoverheid: Digitale autonomie prioriteit voor Belastingdienst (11 June 2026)
- Rijksoverheid: Kamerbrief over overstap kantoorautomatisering naar M365 (2 October 2025)
For information only, not legal advice. Last updated 22 October 2026.
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