A recognised social secretariat is a non-profit association (vzw/asbl) recognised by the Belgian Minister of Social Affairs to file NSSO (RSZ/ONSS) declarations on behalf of employers. Only such an association may collect the social security contributions of its affiliated employers and use the name "social secretariat": that is Article 27 of the Act of 27 June 1969. A social bureau has no such recognition. It does the work and is your point of contact, but it does not collect contributions and does not call itself a social secretariat. Business Centrum is such a social bureau in Ghent, with Acerta, recognised under number 250, as its social secretariat.
Recognised social secretariat or social bureau: the difference in one table
Belgian law knows two kinds of representatives (mandataries) that handle an employer's social security: the recognised social secretariat and the social service provider without recognition. A social bureau is not a legal category. It is an office that runs your HR administration and either acts as a provider itself or works with a recognised secretariat. What a social bureau does for an SME in practice has its own guide. This page is about who may do what.
| Recognised social secretariat | Social service provider without recognition | Social bureau with a recognised secretariat behind it | |
|---|---|---|---|
| Who recognises it? | the Minister of Social Affairs | nobody | not the bureau, but the secretariat |
| Legal form | must be a non-profit association | free | free |
| Name "social secretariat" | yes, reserved | prohibited | prohibited for the bureau |
| Collect and transfer NSSO contributions | yes, exclusive right | prohibited | the secretariat collects |
| File Dimona and DmfA | yes, under your mandate | yes, under your mandate | the secretariat files |
| Guarantee for your contributions | yes, at the National Bank or the Deposit and Consignment Office | no | yes, the secretariat's |
| On the yearly list in the Official Gazette | yes | no | only the secretariat |
| Who pays the NSSO? | you pay the secretariat | you pay the NSSO yourself | you pay the secretariat |
| Your point of contact | the secretariat | the provider | the bureau |
The last column is how Business Centrum works: you talk to us, Acerta files the declarations and collects the contributions. The split per task is on the page about Business Centrum and Acerta.
What the law says about a recognised social secretariat
The rule is in Article 27, paragraph 2, of the Act of 27 June 1969, the act that organises social security for employees. Three sentences do the work (our translation of the official Dutch and French text):
- The use of the name "social secretariat" is reserved exclusively for representatives recognised as a social secretariat under the rules set by the King.
- Recognition gives the social secretariat the exclusive right to collect the contributions owed by its affiliated employers, by bank transfer only, and to pass them on to the National Social Security Office.
- Without that recognition, a social service provider is prohibited from collecting contributions.
Paragraph 1 calls recognised secretariats social service providers too: they are providers with a recognition. Paragraph 3 lets the minister withdraw recognition on a report from the NSSO inspectorate. For example when the secretariat knowingly breaks social law, when it stays below the minimum number of employers or employees for 4 consecutive quarters, or when the quality barometer shows a lasting lack of quality.
The NSSO administrative instructions put it just as briefly: providers are not recognised by the minister and do not enjoy the privileges of recognised social secretariats. Nor may they use the title social secretariat or collect contributions the way recognised secretariats do.
Recognition as a social secretariat: the conditions in the Royal Decree
The conditions are in Articles 44 to 49 of the Royal Decree of 28 November 1969. A secretariat applies to the Minister of Social Affairs, who decides on a report from the NSSO inspectorate. The ministerial decree is published in extract in the Belgian Official Gazette.
| Condition | What the Royal Decree requires | Article |
|---|---|---|
| Legal form | a non-profit association whose sole purpose is to complete its affiliated employers' formalities and inform them | art. 44, § 1, 1° |
| Employers' organisation | a representative employers' organisation as founding member, with at least 2 representatives on the board | art. 44, § 1, 2° |
| Size | at least 300 affiliated employers, or 100 employers with at least 5,000 employees between them | art. 44, § 1, 3° |
| Guarantee | from € 37,184.03 to € 185,920.14, depending on the affiliates' headcount | art. 48, § 1, 2° |
| File | a complete file per employer, kept in Belgium, open to the inspectorate | art. 48, § 1, 3° |
| Company auditor | an independent recognised auditor who checks the financial transactions | art. 48, § 1, 4° |
| Wording | on every document "VZW - Sociaal Secretariaat", the recognition number and the date of the ministerial decree | art. 48, § 1, 7° |
| End of mandate | report the end of an employer's mandate to the NSSO inspectorate at least 15 days before it ends | art. 48, § 1, 9° |
The guarantee covers affiliated employers' losses if the secretariat fails to pass on to the NSSO the money it collected from them. That is the practical value of recognition: you pay a supervised association with a guarantee behind it.
Social secretariat recognition number: how to read and check it
The words "erkend sociaal secretariaat nr." or "secrétariat social agréé n°" followed by a number on a payslip or invoice are the wording that Article 48 of the Royal Decree requires. The Official Gazette publishes the full list every year. The latest list we found appeared in the Gazette of 15 July 2025, with the situation on 20 June 2025. It contains 25 recognised secretariats with an active head office. Branches carry their own number in the same series, such as 251 and 252 at Acerta.
| Number | Name on the list | Head office |
|---|---|---|
| 100 | Group S - Sociaal Secretariaat | Brussels |
| 110 | Attentia | Brussels |
| 120 | Securex, Sociaal Secretariaat | Brussels |
| 150 | Sociaal Secretariaat der Notarissen van België | Brussels |
| 200 | UCM - Secrétariat social | Namur |
| 250 | Acerta | Leuven |
| 280 | SST | Tournai |
| 300 | Partena, Sociaal Secretariaat voor Werkgevers | Brussels |
| 370 | Secrétariat social Le Cap | Chaineux |
| 510 | Liantis ESS | Bruges |
| 540 | Sodalis | Sint-Michiels |
| 600 | Sociaal Secretariaat Easypay | Leuven |
| 640 | SD VZW | Antwerp |
| 650 | Nationale Patroonsdienst | Merksem |
| 710 | Orbiss | Antwerp |
| 750 | Sodibe | Antwerp |
| 810 | Sociaal Secretariaat voor Handel en Ambacht | Sint-Denijs-Westrem |
| 850 | Sodiwe | Mechelen |
| 870 | Accuria | Sint-Niklaas |
| 910 | Centrum voor Loonbeheer | Alken |
| 920 | SSE | Meulebeke |
| 950 | Salar | Kasterlee |
| 960 | Besox | Knokke-Heist |
| 980 | DPS | Aalst |
| 995 | Paycover | Brussels |
Source: Belgian Official Gazette, 15 July 2025, FPS Social Security, list of recognised employers' social secretariats on 20 June 2025. Names and addresses may have changed since. How large each secretariat is, according to its own publications, is in our overview of the largest social secretariats.
To be sure, check three things:
- The number is on the list. A number you cannot find in the Official Gazette is not a recognition. Employers can also request the list from the NSSO inspection directorate.
- The representative in Mahis. The social security application Mahis shows which representative may file declarations for your company. That is the party that files your Dimona declaration and your DmfA. You find your employer number as explained for the NSSO number.
- Who you pay the contributions to. If you pay a secretariat, it must be recognised. If you pay the NSSO directly, you work with a provider or do it yourself.
Non-recognised social secretariat: what a social bureau or provider may and may not do
"Non-recognised social secretariat" is a contradiction in terms: without recognition an office may not call itself a social secretariat. It can be a social service provider or a social bureau.
Allowed. Running your HR administration: collecting hours worked, preparing payroll, drafting contracts, tracking leave and absence, answering your questions. With a mandate you sign and that is reported to the NSSO, a provider may also file the Dimona and DmfA for you. According to the NSSO, the vast majority of employers are represented this way.
Not allowed. Collecting and transferring social security contributions, and using the name social secretariat.
What that changes for you. With a provider without recognition, you pay the contributions to the NSSO yourself and follow up those payments. With a social bureau that uses a recognised secretariat, payment runs through that secretariat, just as with a direct affiliation. In every case the obligations remain yours as the employer: the representative fulfils them in your name. What happens if it makes a mistake is in our guide on a social secretariat mistake.
Supervision: what the NSSO checks at a recognised secretariat
Recognised secretariats are supervised by the NSSO inspectorate. According to the NSSO annual report, it carried out 6,650 investigations at recognised social secretariats in 2025. Since 20 February 2017 a quality barometer applies, with 6 control areas: silent employers, technical checks, financial checks, system checks on priority and other anomalies in the DmfA, and cross-checks between Dimona and DmfA. The financial checks apply only to recognised secretariats. The law allows the other parts to be applied to providers as well.
According to the same report, 83% of employers were affiliated with a recognised social secretariat in 2025. It is not compulsory: you may file your own declarations. What you then take on is explained in is a social secretariat mandatory.
Changing representative: what recognition changes
Whether you move from a recognised secretariat to a social bureau or the other way round, the mandate with the NSSO only transfers at the start of a new quarter. Your old representative must give the new one all the information it needs about previous quarters. A recognised secretariat reports the end of your mandate to the NSSO inspectorate. How to handle it in practice and which notice periods the contracts contain is in changing your social secretariat and social secretariat notice period. If you are a new employer, the guide on joining a social secretariat sets out the steps.
Five misconceptions about recognised social secretariats
- "Every office that runs payroll is a social secretariat." No. Only the 25 associations on the list. Accountants, payroll companies and social bureaus are not, even when they do excellent work.
- "A recognised secretariat takes over my responsibility." It completes the formalities in your name, as your representative. You remain the employer.
- "A social bureau is less safe." That depends on who collects the contributions. If the bureau works with a recognised secretariat, your money runs through that secretariat and its guarantee.
- "The largest secretariat is the best." Size says something about scale, not about who knows your file. How to choose is in which social secretariat to choose and, for Ghent and East Flanders, in how to choose a social secretariat in Ghent.
- "A foreign payroll provider can collect contributions here." Not without Belgian recognition. What such a provider can do is in how to choose a payroll provider in Belgium.
How Business Centrum and Acerta work together
Business Centrum is a social bureau in Ghent, founded in 2013, and a recognised partner of Acerta. We run your HR administration: payroll administration, Dimona, employment contracts and leave. Acerta, recognised under number 250, files the declarations with the NSSO and collects the contributions. What you do directly with Acerta and what goes through us is listed task by task in Acerta or Business Centrum. What it costs to work with a secretariat or a bureau is in social secretariat cost.
Want to know who files declarations for your company today, and whether that is in order? Our social secretariat service reviews it with you. Ask for a call back and Business Centrum will contact you.