Dutch Tax Office Drops Microsoft 365 Cloud For In-House And Open-Source Tools
The Netherlands’ tax authority has abandoned its planned Microsoft 365 cloud rollout in favour of infrastructure it controls and European open-source software, highlighting how concerns about sensitive information and supplier dependence can change major IT decisions.
What Has Changed?
In a letter to parliament dated 5 October, State Secretary for Finance Eelco Eerenberg confirmed that the Belastingdienst, Customs and Benefits services would adopt an on-premises approach combined with open-source tools. On-premises means software runs on servers the authority owns or controls, rather than through a supplier’s public cloud service.
Email and calendars are due to move to that in 2027, followed by European open-source tools for personal storage and collaboration later in 2027 and during 2028. The letter doesn’t name the actual replacement products, and the detailed design and implementation plan are still being developed.
Explaining the intended outcome, Eerenberg writes, “This allows targeted work towards a sustainable and more autonomous solution for these functionalities.” In practice, that should essentially mean giving the authority more control over its systems and data, with less reliance on a single big supplier.
Why Was Microsoft 365 Chosen Originally?
The reversal follows an October 2025 announcement presenting Microsoft 365 as the only realistic option available at the time. The government said maintaining the existing workplace was becoming more expensive, while the expertise needed to support it was increasingly scarce.
The planned move to Microsoft 365 covered everyday staff tools such as email, calendars and document sharing, while the systems used to assess and collect taxes were to remain in the authority’s own data centre in Apeldoorn. The reversal therefore will really only change how employees communicate and work together, rather than where the core tax systems run.
By July 2026, the Dutch government had formally paused the programme while reconsidering an internally hosted alternative. Its latest letter says increased data-centre capacity has helped make that option possible.
What Went Wrong With The Plan?
By January 2026, the new Microsoft 365 setup had reached around 5,000 of the authority’s approximately 47,500 employees. However, an independent review by the Dutch Advisory Council on ICT Assessment, known as AcICT, found that it did not adequately meet the organisation’s needs.
The reviewers identified problems with how sensitive information was classified and protected, as well as gaps in the backups. For example, some encrypted attachments could not be restored without Microsoft 365, while the backup failed to preserve all Teams content and associated information about files and their use.
These weaknesses also raised some questions about how easily the authority could leave the service. The review found no workable exit plan, an incomplete picture of costs and responsibility divided between teams in ways that made the programme harder to manage. Its criticism therefore concerned how the authority had designed and managed this rollout, rather than suggesting that every organisation using Microsoft 365 faces the same problems.
Why Does Supplier Dependence Matter?
The practical concern is whether an organisation can continue working if access to a supplier’s service changes. For example, holding a separate copy of information offers limited protection if staff can’t restore it, open it or understand how it relates to other records.
For a tax authority handling confidential information, those questions concern both privacy and continuity. Greater control over servers may help reduce some dependencies, but it still requires reliable software, skilled staff and tested recovery arrangements.
The revised plan therefore considers different tools for different functions. Eerenberg’s letter says, translated from Dutch, that this follows advice “not to assume one solution from one supplier, but to examine alternatives for each functionality”.
What Will Be Difficult About Switching?
The authority intends to reuse existing licences where possible to limit additional investment. However, changing direction doesn’t actually remove the need to modernise, and the letter acknowledges that the revised approach affects both the replacement timetable and planned records-management improvements.
Some capabilities intended to help organise and retain information were included in the Microsoft 365 package but are unavailable on-premises. The authority says it’s still assessing how to replace them and has promised a further update.
That matters because storing documents is only part of managing them properly. Staff also need to find the correct version, apply retention rules and preserve records required for accountability.
What Does This Mean For Your Business?
For businesses, the useful lesson from all this is to examine what each service must deliver before choosing where it runs. Email, customer records and collaborative documents may have different requirements. Decisions should account for sensitivity, availability, integration and support, rather than assuming either cloud or on-premises hosting is automatically the safer choice.
Exit planning should also involve practical tests. Businesses should establish what they can export, whether permissions and document history survive, and how quickly staff could resume work elsewhere. A backup that depends on continued access to the original service may provide less independence than expected. Suppliers should explain those limitations before contracts become difficult to leave.
Also, compare the full cost of each option, including migration, training, maintenance, security and records management. Open-source software can offer flexibility, but somebody still needs to support it and keep it secure. The Dutch decision shows why reviewing an earlier choice can be sensible, provided the replacement is assessed just as carefully and delivers the control, usability and continuity the organisation actually needs.
