How to Start a Plumbing Business in the UK

Starting a plumbing business in the UK as a sole trader involves a few specific regulatory requirements - particularly around gas work - that you need to have in place before taking on customers.

This guide covers Gas Safe registration, insurance, HMRC setup, and everything else you need to trade professionally from day one.

Do you need to be registered to work as a plumber in the UK?

For general plumbing work - cold water supply, drainage, above-ground pipework, bathroom fitting - there is no mandatory registration in the UK. Any competent person can legally carry out water and drainage plumbing.

For gas work, registration with the Gas Safe Register is a legal requirement.

Gas Safe Register - what it is and how to register

The Gas Safe Register is the official UK gas registration body, appointed by the Health and Safety Executive (HSE). It replaced CORGI in 2009. Carrying out gas work without Gas Safe registration is a criminal offence that can result in prosecution, unlimited fines, and imprisonment.

To register with Gas Safe, you need:

• Relevant gas qualifications - typically ACS (Accredited Certification Scheme) assessments. These cover specific categories of gas work: domestic natural gas (CCN1), domestic appliances (CEN1), gas pipework (CENWAT), and others depending on what you intend to work on
• Gas Safe registration application and fee
• Public liability insurance

Gas Safe cards specify exactly what categories of gas work you are qualified and registered to carry out. Your card must be current and visible when carrying out gas work. Customers can check your registration on the Gas Safe website.

ACS assessments are carried out at approved assessment centres. They must be renewed every 5 years.

G3 qualification for unvented hot water systems

Working on unvented (pressurised) hot water storage systems requires a separate G3 qualification under Building Regulations Part G. This applies to pressurised cylinders such as mains-pressure hot water tanks.

G3 work without the qualification is illegal and unsafe. If you intend to install or service unvented systems, you must hold and be able to evidence this qualification.

Professional memberships - APHC, CIPHE

Professional body membership is not mandatory, but it adds credibility and opens commercial opportunities:

• APHC (Association of Plumbing and Heating Contractors) - trade association with a find-a-contractor directory, training resources, and technical support. Requires evidence of qualifications and insurance.
• CIPHE (Chartered Institute of Plumbing and Heating Engineering) - the professional body. Membership indicates a higher level of professional standing and is increasingly expected by commercial customers.

Insurance: what you need before trading

Public liability insurance is not legally required for general plumbing work but is essential in practice:

• Gas Safe registration requires it
• Most commercial customers require proof of insurance before hiring you
• Water damage claims can be extremely high - even a small leak can cause tens of thousands of pounds in damage

Standard minimum coverage for a plumber in the UK is £1 million to £2 million public liability. Many commercial customers require £5 million or more.

If you employ anyone, employers liability insurance is a legal requirement (minimum £5 million under UK law).

HMRC registration: tax and VAT

Register as self-employed with HMRC through your Personal Tax Account online. You will need to file a Self Assessment tax return each year. See our guide on setting up as a sole trader for the general framework (the process is similar in the UK).

For VAT: most UK plumbing work is subject to 20% standard rate. The 5% reduced rate applies to heating system installation in domestic properties. You must register for VAT when your annual taxable turnover exceeds £90,000. See our UK VAT guide for tradesmen.

If you work as a subcontractor on construction jobs, you will also need to register with the Construction Industry Scheme (CIS). See our CIS guide for UK tradesmen.

What you need before your first job

• Gas Safe registration (if doing gas work) - check this is done before the first gas job
• G3 qualification (if doing unvented hot water system work)
• Public liability insurance certificate
• HMRC Self Assessment registration
• VAT registration if required (£90,000 threshold)
• CIS subcontractor registration (if working for contractors)
• Professional invoicing set up
• Trade account with your main supplier

Quoting and invoicing as a UK plumber

Every job should have a written quote before work starts and a proper invoice after. This is your protection against price disputes, scope creep, and late payment.

See our guides on how to quote a boiler replacement and how to quote a bathroom installation for the practical detail.

Download a free plumber invoice template for UK or get early access to PayReady - it's free. PayReady generates professional plumbing quotes and invoices from your phone with the correct VAT rate pre-set.

Summary: starting a plumbing business in the UK

1. Get Gas Safe registered before carrying out any gas work
2. Obtain G3 qualification for unvented hot water system work
3. Take out public liability insurance (minimum £2m)
4. Register with HMRC for Self Assessment
5. Register for VAT when turnover approaches £90,000
6. Register with CIS as a subcontractor if working for contractors
7. Set up professional invoicing before the first job