Algorithm Correctness of employee insurance and health insurance contributions

Dutch Tax and Customs Administration

This page contains information about the algorithm Correctness of employee insurance and health insurance contributions. The algorithm supports Tax and Customs Administration employees in monitoring differences between the premiums declared in the submitted wage return and the calculated premiums. The algorithm helps Tax Administration employees react to possible discrepancies.

Last change on 2nd of July 2025, at 11:03 (CET) | Publication Standard 1.0

• Publication category: Impactful algorithms
• Impact assessment: Field not filled in.
• Status: In use

General information

Theme

Public finance

Begin date

Field not filled in.

Contact information

[e-mail]

Link to publication website

https://over-ons.belastingdienst.nl/onderwerpen/omgaan-met-gegevens/algoritmeregister/

Link to source registration

https://over-ons.belastingdienst.nl/onderwerpen/omgaan-met-gegevens/algoritmeregister/algoritme-juistheid-premie-werknemersverzekeringen-en-zorgverzekeringswet/

Responsible use

Goal and impact

The Tax Authority checks withholding agents for correct and complete declaration and payment of payroll taxes. Payroll taxes consist of wage tax, national insurance contributions, employee insurance and the income-related Healthcare Insurance Act contribution. Withholding agents (such as an employer, pension fund or benefits agency) deduct wage tax and national insurance contributions, and in some cases the income-related Healthcare Insurance Act contribution, from their employee's wages. They remit these to the tax authorities. The employee insurance contributions and usually the income-related Healthcare Insurance Act contribution are not deducted from the employee's wage, as the employer itself remits these to the Tax Office.

The algorithm looks at the contribution data from the wage tax return, which relate to employee insurance and health insurance. It calculates what the amount of the contributions should be. This is done on the basis of the declared premium wage for employee insurance and the calculated contribution wage for the Health Insurance Act.

These contribution amounts are compared with the contribution amounts indicated in the wage declaration. Verification of the amounts takes place periodically. Both positive and negative differences identified are looked at.

The premium data are part of the employee data processed by the Tax and Customs Administration and the UWV. A general description of how the Wage Return Chain works is published on the Wage Return Chain website. (https://www.loonaangifteketen.nl/ )

Based on the clues from the algorithm, the handler can assess the difference between the calculated premium and the declared premium. It is the Inland Revenue handler who ultimately determines whether there is a difference. If necessary, the handler can contact the withholding agent to further explain the difference with a request to the withholding agent to correct the differences.

Considerations

Monitoring the differences between the declared premium amounts according to the submitted wage return and the calculated premium amounts is important for the withholding agent. Because this is the way to achieve correct premium and data delivery in the wage declaration. We want to do this monitoring carefully. The algorithm can support a Tax Administration employee in this. Based on the differences indicated by the algorithm, the assessment is therefore more careful, efficient and uniform.

Human intervention

Human intervention in the Tax Administration context implies that a competent and knowledgeable employee plays a substantial role in decision-making.

The operation of the algorithm always involves human intervention. The algorithm detects and selects. It is the Tax Administration employee who makes the decision whether to contact the withholding agent.

Risk management

The General Administrative Law Act (Awb) requires the government's actions to be transparent and lawful. The Tax Administration observes the general principles of good governance when applying and developing algorithms.

The algorithm uses data collected under various tax laws. As required by the AVG, no more data is used than necessary.

The selection rules are reviewed periodically and adjusted if necessary to remain compliant with laws and regulations.

Legal basis

1. General State Tax Act:
2. General Administrative Law Act:
3. General Data Protection Regulation:
4. General Data Protection Regulation Implementation Act:
5. Payroll Tax Act 1964:
6. Social Insurance (Funding) Act:
7. General provisions Citizen Service Number Act:
8. Archives Act 1995:
9. Recovery Act:
10. Unemployment Act:
11. Sickness Act:
12. Work and Income according to Labour Capacity Act:
13. Disability Insurance Act:
14. Health Insurance Act:
15. Work and Income Implementation Structure Act:

Links to legal bases

• Algemene wet inzake rijksbelastingen: : https://wetten.overheid.nl/BWBR0002320/
• Algemene wet bestuursrecht: : https://wetten.overheid.nl/BWBR0005537/
• Algemene verordening gegevensbescherming: : https://eur-lex.europa.eu/legal-content/NL/TXT/HTML/?uri=CELEX:32016R0679
• Uitvoeringswet algemene verordening gegevensbescherming: : https://wetten.overheid.nl/BWBR0040940/
• Wet op de loonbelasting 1964:: https://wetten.overheid.nl/BWBR0002471/
• Wet financiering sociale verzekeringen:: https://wetten.overheid.nl/BWBR0017745/
• Wet algemene bepalingen Burgerservicenummer:: https://wetten.overheid.nl/BWBR0022428/
• Archiefwet 1995: : https://wetten.overheid.nl/BWBR0007376/
• Invorderingswet:: https://wetten.overheid.nl/BWBR0004770/
• Werkloosheidswet:: https://wetten.overheid.nl/BWBR0004045/
• Ziektewet:: https://wetten.overheid.nl/BWBR0001888/
• Wet werk en inkomen naar arbeidsvermogen:: https://wetten.overheid.nl/BWBR0019057/
• Wet op de arbeidsongeschiktheids verzekering:: https://wetten.overheid.nl/BWBR0002524/
• Zorgverzekeringswet:: https://wetten.overheid.nl/BWBR0018450/
• Wet structuur uitvoeringsorganisatie werk en inkomen:: https://wetten.overheid.nl/BWBR0013060

Elaboration on impact assessments

• Privacy and AVG

The use of data is tested against the General Data Protection Regulation (AVG). Reviewing personal data reveals any privacy risks and allows appropriate measures to be taken.

The AVG prescribes that no more data should be used than necessary. This is called data minimisation. The Tax Administration regularly examines whether the data used are still necessary and may therefore be used.

• Use of special personal data

The algorithm accuracy of employee insurance contributions and health insurance law does not use special personal data.

• Equality and non-discrimination

The algorithm is assessed in line with applicable non-discrimination principles for direct and indirect discrimination. The selection rules assess only the declared contribution rates and employee insurance contributions. Processing as little personal data as possible reduces the risk of direct discrimination. Employees involved in developing and managing the algorithms receive training on data protection and bias.

Operations

Data

1. Identifying data (including LH number)
2. Payroll tax details
3. Payroll tax return details
4. Premium percentages, maximum contribution payroll taxes

Links to data sources

• Identificerende gegevens (o.a. LH-nummer): Belastingdienst
• Relatiegegevens Loonheffingen: Belastingdienst
• Aangiftegegevens Loonheffingen: Belastingdienst
• Premiepercentages, maximum premieloon Loonheffingen: Belastingdienst

Technical design

The algorithm consists of selection rules created by content experts based on laws, regulations and expertise.

The algorithm is not self-learning. That means it does not evolve as it is used.

External provider

The algorithm was developed by Tax Administration staff and is also maintained internally.