An installation company needs two statutory certificates, depending on the work. To install, repair and maintain boilers, water heaters and gas fires, the business must be CO certified and the fitter must hold a Proof of Competence. For work on the refrigerant of a heat pump or air conditioner, a BRL 100 company certificate and a BRL 200 personal certificate are required. There is no certificate for drinking water, but there is a statutory standard.
In short
- Only a CO certified business may work on gas appliances. The client who hires someone else is also liable to penalties.
- For refrigerant you need BRL 100 for the business and BRL 200 per fitter. Since 2025 this also applies to propane and CO₂.
- Drinking water work must meet NEN 1006. No certificate is needed for it, but clients and insurers may ask for a recognition.
In this article
- Which certificates are required by law for an installation company?
- What does CO certification for work on gas appliances involve?
- Where does CO certification stand in 2026?
- Which F-gas certificates do you need?
- What does F-gas Regulation 2024/573 change for servicing in 2026?
- Which rules apply to work on drinking water installations?
- What do the insurer and the client ask of an installation company?
Which certificates are required by law for an installation company?
Plumber or installer is not a protected profession in the Netherlands. The requirement lies in certain types of work. A certificate is required for work on gas combustion appliances and for work with refrigerants. Not for drinking water, sanitary fittings and indoor drainage, but there the Buildings (Living Environment) Decree prescribes standards.
Besides the requirements there are voluntary recognitions, such as InstallQ's for Gas or Water. Techniek Nederland writes that recognition is not required by law, but that quality schemes sometimes become mandatory through insurers' requirements (Techniek Nederland). At InstallQ a recognition costs a one-off €285 registration in 2026 and €141 per field per year (InstallQ).
What does CO certification for work on gas appliances involve?
Only a certificate holder may install, repair, maintain and commission a gas combustion appliance. This also covers the combustion air supply and the flue gas outlet. That is what Article 6.45 of the Buildings (Living Environment) Decreesays. It concerns boilers, water heaters, gas fires and gas stoves.
The rule applies to whoever carries out the work and to whoever has it carried out. Ondernemersplein writes that working without a CO certificate is a criminal offence, and that the client who commissions the work is also liable to penalties (Ondernemersplein). A housing association or contractor that hires you therefore has its own interest in your certificate being valid.
Certification has two tracks. The business works to an assessment guideline, such as InstallQ's BRL 6000-25 or Kiwa's BRL K25000, with a quality manual and an audit by a certification body. The business is then listed in the register of gas combustion installations and uses the CO-VRIJ logo (Ondernemersplein). An assessment guideline is a set of requirements against which the certification body tests the business.
The fitter needs a Proof of Competence. The fitter obtains it through a theory test and a practical exam. It is valid for 5 years and is stored in the Vakpaspoort Techniek app (Vakmanschap CO). Make sure every fitter carries the Vakpaspoort, because a client may ask for identification.
If a certificate holder measures more carbon monoxide than the statutory limit in a space where people may be present, the certificate holder reports it immediately to the occupant and the owner, the municipality and the certification body (Article 6.46 Buildings (Living Environment) Decree). The limit itself is set in a ministerial regulation.
Where does CO certification stand in 2026?
The requirement has applied since 1 April 2023 and remains unchanged in 2026. A 2024 evaluation found that the system had not been in place long enough to say anything for certain about its effectiveness. The researchers did see that the quality of work at certified businesses has improved (letter to parliament on the CO system evaluation).
According to the same letter, by the end of 2024 more than 3,100 businesses were certified and about 23,000 fitters had obtained their proof of competence. Costs for self-employed people and small firms turned out higher than expected. Rates charged to consumers have risen, partly because of the system and partly because of higher staff and material costs (letter to parliament on the CO system evaluation).
In July 2025 the ministry announced a few changes. Municipalities will only be notified of a near-accident if the installer has not resolved the problem immediately. There will be no statutory requirement for periodic boiler maintenance. Initiatives are under way to make things simpler for the self-employed and small firms, such as apps and a review of the certification schemes (Volkshuisvesting Nederland).
Supervision lies with the municipality as the competent authority. The ministry entered talks with municipalities about whether they can supervise enough (letter to parliament on the CO system evaluation). A client, principal or insurer can consult the register themselves.
What the certificate costs depends on the certification body. There is no fixed price. In 2026 InstallQ does charge the certification body a levy of €277 a year for a business with up to 6 FTE field staff holding only the basic certificate and sub-area 25 (InstallQ). So ask more than one body for a quote.
Which F-gas certificates do you need?
Anyone working on the refrigerant circuit of a heat pump or air conditioner needs a BRL 200 personal certificate. The business needs a BRL 100 company certificate. A self-employed person needs both (ILT). A refrigerant is the substance in the closed circuit that moves heat.
The requirement covers installation, servicing, maintenance, repair, leak checks, decommissioning and recovery. Installations with F-gases must be checked for leaks every year by someone with the right certificate. You keep the logbook for 5 years (Ondernemersplein). In the Centraal Register Techniek a client can see whether your business and your fitters are certified.
Under the new European rules the certificate requirement also applies to natural refrigerants, such as propane, CO₂ and ammonia (IPLO). According to the trade association NVKL this has been mandatory since 29 September 2025. Anyone certified under the old rules must recertify for the first time before 12 March 2029, and every 7 years after that (NVKL). For a business that installs propane heat pumps, this is new.
In a monobloc heat pump the refrigerant circuit is sealed at the factory. Techniek Nederland writes that no mandatory certification applies to monobloc systems, but that it does for split systems (Techniek Nederland). The government pages do not mention that exception. If your fitter does open the circuit, the requirement certainly applies.
The ILT checks whether fitters and businesses hold a valid certificate and imposes a sanction if one is missing (ILT). According to IPLO, a business that hires a fitter or subcontractor for refrigerant work must establish that they hold the right certificates (IPLO).
What does F-gas Regulation 2024/573 change for servicing in 2026?
Since 1 January 2026 you may no longer refill air conditioners and heat pumps with virgin refrigerant with a GWP above 2,500. Until 2032 it is still allowed with recycled or reclaimed refrigerant (IPLO). GWP stands for global warming potential: how strongly a gas warms the climate compared with CO₂.
The regulation has applied since 11 March 2024. The quota system reduces the quantity of HFCs on the European market step by step, to zero in 2050 (European Commission). HFCs are the most widely used F-gases in refrigeration and heat pumps.
So with a maintenance contract for older air conditioners or heat pumps with such a refrigerant, from 2026 you can no longer solve every leak by refilling. Set out in the contract what you will do if the unit may no longer be refilled, and discuss replacement with the client in good time.
Which rules apply to work on drinking water installations?
No certificate is required for drinking water work. A drinking water and hot water installation must meet NEN 1006, for existing buildings and new builds (Articles 3.109, 3.110, 4.202 and 4.203 Buildings (Living Environment) Decree). NEN 1006 is the standard for tap water installations. Anyone who does not follow that standard delivers work that does not comply with the law.
The owner of a domestic installation ensures that the installation poses no risk of contaminating the mains and the drinking water (Article 31 Drinking Water Act). In practice the owner therefore expects you to get backflow protection and materials right. Record what you did, for example with a pressure test and a completion report.
Strict legionella rules apply only at priority locations, such as care institutions, swimming pools, hotels and guesthouses with more than 5 beds, and campsites. There a business with a BRL 6010 certificate draws up the risk analysis and the management plan, and the water is sampled every six months (Ondernemersplein). These rules do not apply to an ordinary home. Legionella grows in water between 25 and 55 degrees.
Dutch research showed that a new appliance can also be a source. Of 23 patients with Legionnaires' disease between May 2022 and August 2023, 21 had received a new flow-through water heater of one brand less than six months earlier. The same legionella strain was found in the homes of 20 of the 21 patients investigated (Reukers and others, 2026). The researchers point out that disinfection after installing a water heater is not mandatory in the Netherlands.
The study concerns one brand and one outbreak and does not prove that every new appliance is a risk. The lesson is still useful for how you work: follow the manufacturer's instructions when commissioning, flush the pipes and record the hot water temperature at the furthest tap.
What do the insurer and the client ask of an installation company?
A business client may ask for proof of certificates, because with gas work the client can be liable to penalties itself (Ondernemersplein). With refrigerant work, a business that contracts out work must establish the contractor's certificates (IPLO). So keep a folder ready with your certificates, register numbers and your fitters' Vakpaspoorts.
Business liability insurance (AVB) is not mandatory, but a client or trade association may ask for it. Insurers use your SBI code among other things to set the premium. If you do work that does not match your registered activities, that can affect your cover (KVK). The SBI code is the code for your activities in the Business Register.
So ask your insurer whether work on gas appliances and refrigerant is covered by the policy, and what happens if a certificate expires. Ask about care, custody and control as well. That is damage to something you are working on, such as the boiler you are servicing. According to Techniek Nederland, many standard liability policies exclude it (Techniek Nederland).
Five things to have ready
Your CO certificate and register listing, the Proof of Competence of every fitter who works on gas, BRL 100 and BRL 200 if you work on refrigerant, a policy that covers gas and refrigerant work, and a completion report for each drinking water job.
Sources
- Buildings (Living Environment) Decree (Besluit bouwwerken leefomgeving), Articles 3.109, 3.110, 4.202, 4.203, 6.45 and 6.46, in force from 24 September 2026. wetten.overheid.nl
- Techniek Nederland, Quality schemes, consulted 28 October 2026. technieknederland.nl
- InstallQ, InstallQ 2026 rates, consulted 28 October 2026. installq.nl
- Ondernemersplein, CO certificate (carbon monoxide) for heating engineers, consulted 28 October 2026. ondernemersplein.overheid.nl
- Vakmanschap CO, Proof of Competence, consulted 28 October 2026. vakmanschapco.nl
- Minister of Housing and Spatial Planning, letter on the evaluation of the CO system, parliamentary paper 32 757, no. 190, 19 November 2024. officielebekendmakingen.nl
- Volkshuisvesting Nederland, Changes to the CO system: improved reporting of near-accidents, 4 July 2025. volkshuisvestingnederland.nl
- Human Environment and Transport Inspectorate (ILT), Certificates for working with F-gases and ozone-depleting substances, consulted 28 October 2026. ilent.nl
- Ondernemersplein, Certificate for working with F-gases, consulted 28 October 2026. ondernemersplein.overheid.nl
- IPLO, Ozone and F-gases: installers, consulted 28 October 2026. iplo.nl
- NVKL, F-gas Regulation flyer, Regulation (EU) 2024/573, version 3 February 2026. nvkl.nl
- Techniek Nederland, From gas boiler to heat pump installer in 5 steps, consulted 28 October 2026. technieknederland.nl
- European Commission, F-gas legislation, consulted 28 October 2026. climate.ec.europa.eu
- Drinking Water Act (Drinkwaterwet), Article 31, in force from 1 January 2024. wetten.overheid.nl
- Ondernemersplein, Preventing legionella, consulted 28 October 2026. ondernemersplein.overheid.nl
- Reukers, D.F.M., Euser, S.M., Bartels, A.A., Keet, M.G., Boot, M., Ruijs, W.L.M. and Brandsema, P.S. (2026). Outbreak of Legionnaires' disease linked to newly installed residential water heaters, the Netherlands, 2022-2023. Emerging Infectious Diseases, 32(7), 1039-1045. doi.org
- KVK, Do I need business liability insurance?, updated 17 August 2026. kvk.nl
- Techniek Nederland, Are you covered for care, custody and control during repairs?, 6 January 2025. technieknederland.nl