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HR & Recruitment calendar_today Updated: 15 September 2026 schedule 3 min read

Can I Use and Keep an Employee's National Identification Number?

verified Last reviewed 15 September 2026 · GDPRWise legal team

You may process the number when that is necessary and legally permitted for social security, payroll or other legal obligations, but not as a general internal identifier.

summarize Key Takeaways
  • check_circle Map every storage location and every disclosure of the number to a statutory purpose
  • check_circle Remove the number from systems in which an internal employee number is sufficient
  • check_circle Never use the number as an employee number, username, password or visible badge number
  • check_circle Share it only with parties that need it for a permitted purpose, such as your payroll provider or a competent public authority

You may use an employee’s national identification number (in Belgium the rijksregisternummer, also called the INSZ number) when that is necessary and legally permitted for personnel and payroll administration. But not as a general internal identifier.

What you need it for

Employers need the number, among other things, for social security declarations and for certain social and tax documents. In Belgium, for example, that is the Dimona declaration, which identifies the employee and establishes the link between employee and employer. For certain people without a national register number, Belgian social security assigns a BIS number.

Use the number solely for the statutory or administrative purposes for which you need it. The existence of an employment relationship does not give you a general right to use the number across all your HR systems.

The number is not a special category of data within the meaning of Article 9 GDPR, but it is a specifically protected national identification number. The Belgian data protection authority describes the national register number as an identifier whose use requires a statutory basis or authorisation; other member states have comparable restrictions for their national number.

What you do not do

So do not use the number as a general employee number, username, password, visible number on badges or general key to link files. Assign every employee a separate internal employee number.

Share the number only with parties that need it for a permitted purpose, such as your payroll provider or a competent public authority.

Map it

Map every storage location and every disclosure of the number to a statutory purpose, and remove it from systems in which an internal employee number is sufficient. Which other data from the identity card you may record is explained in Which data from an employee’s identity card may I record?

Use of the number falls under the principles of purpose limitation and data minimisation (Article 5(1)(b) and (c) GDPR) and relies on a legal obligation as its legal basis (Article 6(1)(c) and 6(3) GDPR). Article 87 GDPR lets member states set specific conditions for processing a national identification number, and Article 32 GDPR requires you to secure it appropriately. In Belgium, the Act of 8 August 1983 organising a National Register of natural persons and the social security and tax legislation apply on top of that.

auto_awesome Do you know where the national number sits in your systems?

GDPRWise maps your HR processes and systems, so you can confine sensitive identifiers to the places where they belong.

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This article was written by the GDPRWise team and reviewed by our privacy experts. We regularly review our content for accuracy and legal correctness.