NEN 4400 audit: how the inspection works step by step
In practice, a NEN 4400 audit is an inspection of your personnel, payroll and financial records by an inspection body. It tests your company against NEN 4400-1 or NEN 4400-2, depending on where you are established. According to Kiwa , the inspection focuses on three pillars: personnel records, payroll records and financial records. If the result is positive, the company is then listed in the SNA register .
This page describes how such an inspection works, what the auditor wants to see and which mistakes often lead to findings. To choose the standard part, read NEN 4400-1 versus NEN 4400-2 first. For the application itself, see applying for the SNA certificate.
Last checked: 28 October 2026.
What exactly is a NEN 4400 audit?
The market uses the word “audit” loosely. SNA (Stichting Normering Arbeid, the Dutch Foundation for Labour Standards) itself speaks of an inspection. An inspection body accredited by the RvA (Raad voor Accreditatie, the Dutch Accreditation Council) checks your records against the standard. It is not a management system audit like the one for ISO 9001. The inspector does not review quality manuals. The inspector looks for evidence that you work the way the standard describes.
The difference from the requirements checklist matters. You use the checklist to prepare. The audit is the moment when someone from outside looks at your records, and every document must match the others.
The process in six steps
The order below follows the steps that Kiwa describes. Other inspection bodies may have small differences.
Registration with SNA and choosing the inspection body
You first register with SNA and choose an inspection body. According to SNA, a first inspection can only take place once you have been active for at least three months and have made wage payments or tax remittances. Kiwa says the inspection can start within four weeks of the application. That is Kiwa’s statement about its own offer, not a rule from SNA or the law.
Supplying documents in advance
The registration requires a Chamber of Commerce extract (KvK-uittreksel) that is no more than three months old, according to the SNA FAQ . The inspection body decides which other documents you send in advance. Make sure the legal name is the same everywhere.
The inspection on site or remotely
The inspector goes through your records. They select a sample of staff and assignments and follow each one from start to finish: from registration, through hours and pay, to payment and tax returns. A person responsible within your company is often also interviewed.
Findings and deviations
Every deviation is recorded. Examples include a missing identity check, a timesheet that does not match the pay, or a payment without a traceable assignment. Not every deviation means you fail. SNA does not set a fixed deadline for correcting findings in its FAQ, but it advises fixing mistakes as quickly as possible. Your correction must cover the whole affected group of files, not only the files where the error was found.
Correction and check
You correct the deviation and record clearly what you changed. The inspector then checks whether the correction works. At a follow-up inspection, the inspector often looks again at the same parts.
Decision and declaration
The report goes to an assessor who decides on the certification. If the decision is positive, the company is listed as certified in the SNA register. You can then download the declaration of registration. Until you have a positive result, your company can be on the list of ongoing applications for up to three months at most. See checking the SNA register for how to check the status yourself.
Which documents does the auditor ask for?
An inspector looks for coherence. They want to see that one person or one assignment matches across all records. The table below is a working overview based on what SNA and Kiwa mention: identity, tax returns, payment of wages, right to work, and the link between hours, pay and invoices. The inspection body decides the exact selection.
| Area | What the auditor wants to see | Commonly requested evidence |
|---|---|---|
| Identity and right to work | Check carried out before the first deployment | Copy of identity document, check note |
| Employment contract | Agreements are recorded in writing | Signed contract, collective labour agreement (cao) classification |
| Hours | Hours worked are authorised | Timesheet with signature or approval |
| Pay | Pay matches hours and legislation | Payslip, payroll journal |
| Payment | Payments can be traced to staff | Bank statement, payment list |
| Tax returns | Payroll taxes (loonheffingen) and VAT match the records | Return, confirmation of receipt |
| Direction | Clear who directs the work | Assignment, hirer’s contract |
A fictional sample example
Staffing agency Delta selected one employee during an inspection. The inspector chooses one assignment, for example 120 hours in March at client Noord. They ask for the timesheet, the payslip, the payroll journal, the payment to the employee and the invoice to the client.
If the timesheet shows 120 hours but the payslip shows 116 hours, that is a deviation. It may be a justified correction, but only if the correction is in the file with a date and a reason. This example is fictional and is meant to show how the process works.
The inspector does not only check whether a document exists. They check whether the figures match. A correction with a date and reason in the file can explain a difference. A difference without an explanation remains a deviation.
Common mistakes
- Different names or numbers. The legal name on the contract differs from the one on the payslip or the Chamber of Commerce extract.
- Missing corrections. A change in the time registration was made, but the original value was thrown away. Always keep corrections.
- Loose documents. An identity document was checked, but there is no date or initials on it.
- Unclear division of roles. When hiring out staff, it is not recorded who directs the work. This makes the choice of module harder.
- Documents only for the inspection. A folder is prepared that does not match the actual records. The sample follows the real chain, not the folder.
How do you prepare for the audit?
- Choose one recent assignment and follow it through your entire administration. If you cannot do that in one day, there is a gap.
- Keep a log of deviations and corrections, with a date and a person responsible.
- Make sure one person can answer the inspector’s questions about the chain and the administration.
- Make an overview of your modules and activities, so the inspection matches your contracts. See applying for the SNA certificate for the modules.
Frequently asked questions
How often does an inspection take place?
According to Kiwa, inspections normally take place every six months. Under certain conditions, a yearly frequency is possible. SNA does not state a frequency in its FAQ, so this is Kiwa’s statement. Check the frequency with your own inspection body. See the validity of the certificate for what happens if a follow-up inspection does not take place.
Can I have an audit without having staff?
That depends on your activity. Since November 2025, SNA has had a separate standard for intermediary services with self-employed workers, which is read together with NEN 4400-1 or -2. See NEN 4400 for self-employed workers.
Is an internal audit the same as an inspection?
No. An internal check helps you prepare. The inspection is carried out by an inspection body accredited by the RvA. See inspection and accreditation for the roles.