The Netherlands Tax and Customs Administration plans a phased shift away from its Microsoft 365 cloud migration: email and calendars are scheduled to move on-premises in 2027, followed later in 2027 and in 2028 by European open-source services for personal storage and collaboration. A government letter dated October 5, 2026, and submitted by State Secretary for Finance Eelco Eerenberg, sets out the planned timetable.
The stages concern specific services, with email and calendars scheduled first. The timetable describes future plans, not a completed migration.
Email and calendars are scheduled first
The administration selected Microsoft 365 in 2025. Its earlier rollout had reached about 5,000 of 47,500 employees across tax, customs and benefits services, according to the reported figures. Under the new schedule, email and calendars are planned to move to on-premises operation in 2027. On-premises services run on infrastructure managed locally by the organization.
European open-source solutions for personal storage and collaboration are planned to follow later in 2027 and in 2028. The shift toward locally controlled systems and European software reflects a broader push for digital sovereignty: greater control over data, infrastructure and dependence on suppliers.
Concerns about the selected cloud design
The Dutch Advisory Council on ICT Assessment raised concerns about the selected public-cloud design, including information security, information processing and future flexibility. The concerns about encryption relate to the configuration chosen for the administration: end-to-end encryption was not enabled by default for one-to-one Teams calls and was unavailable for group calls. Those settings describe that configuration, not every Microsoft 365 setup.
The council also criticized reliance on standard Microsoft encryption rather than Double Key Encryption for sensitive information. Broader concerns included dependence on a single supplier, control of confidential information and the ability to change course later.
Capacity and remaining work
The administration expects increased data-center capacity to make local hosting possible and plans to reuse existing licenses where it can, limiting additional investment. Some planned Microsoft 365 capabilities reportedly have no on-premises equivalent, and the administration is still assessing replacement options and records-management implications.
