| Green Stag Real Estate Limited | Real estate | 2025 |
| Greenacres Equestrian 1 Limited Liability Partnership | | 2015 |
| Greenfield Land & Property Ltd | Construction | 2025 |
| Greenfield Projects and Developments Limited | Construction | 2015 |
| Greengage Tree Limited | Information & communication | 2018 |
| Greenhalgh Limited | Professional & scientific | 2025 |
| Greenloaning Partners Limited | Professional & scientific | 2023 |
| Greenloaning Properties Limited | Real estate | 2017 |
| Greenoak House Residential Management Company Limited | Real estate | 2013 |
| Greenprint Design and Build Ltd | Construction | 2026 |
| Greenstar Management Limited | Administrative & support | 1997 |
| Gregory Fenton Limited | Real estate | 1962 |
| Gretta Ford Consultancy Ltd | Professional & scientific | 2023 |
| Grey Havens Investment Management Limited | Real estate | 2020 |
| Grey State Advisors Limited | Information & communication | 2026 |
| Greyhammer Consulting Ltd | Professional & scientific | 2016 |
| Groom Court Owners Limited | Households | 2003 |
| Groomsport Services Ltd | Hospitality | 2019 |
| Groupmove Ltd | Information & communication | 2025 |
| Grove Home Developments Limited | Real estate | 2021 |
| Grove Home Property Investments Limited | Real estate | 2024 |
| Grove Road Management (Harpenden) Limited | Households | 1972 |
| Gruntled Limited | Information & communication | 2006 |
| GS Land Development Limited | Construction | 2017 |
| GSD Consulting Limited | Information & communication | 2026 |
| Guardsman Guided Walks Ltd | Administrative & support | 2025 |
| Gullwing Communications Limited | Professional & scientific | 2020 |
| Gyrohold Limited | Professional & scientific | 1985 |
| H & H Pubco Ltd | Hospitality | 2025 |
| H ADV LLP | | 2012 |
| H.D.Culley & Company Limited | | 1955 |
| H2 Capital Ltd | Professional & scientific | 2021 |
| Haddenham Flat Management Company Limited | Households | 1983 |
| Haddon Court (Management) Company Limited | Other services | 1965 |
| Haines Media Limited | Information & communication | 2021 |
| Hales Park Management Company Limited | Households | 1983 |
| Haley Bridge Limited | Administrative & support | 2017 |
| Halgabron House Limited | Households | 2004 |
| Halit Yilmaz Ltd | Real estate | 2020 |
| Halo Advertising Limited | Professional & scientific | 2013 |
| Halo Group Africa Ltd | Construction | 2025 |
| Halstead RCS Ltd | Professional & scientific | 2015 |
| Hamilton East Limited | Financial services | 2026 |
| Hamilton EYE Practice Ltd | Health & social care | 2014 |
| Hampstead Legal Consulting Limited | Professional & scientific | 2024 |
| Hanover Grange Limited | Real estate | 2004 |
| Harding Court Freehold Limited | Households | 2018 |
| Hareta Limited | Information & communication | 2023 |
| Harlyn Consulting Ltd | Professional & scientific | 2025 |
| Harmony Way Ltd | Administrative & support | 2021 |
| Harp Property Services Limited | Real estate | 2008 |
| Harpenden Aesthetics Group Limited | Financial services | 2024 |
| Harpenden Aesthetics Ltd | Health & social care | 2010 |
| Harpenden and District Indoor Bowling Club Limited | Arts & recreation | 2017 |
| Harpenden Beauty Limited | Other services | 2026 |
| Harpenden Bedrooms Limited | Wholesale & retail | 2020 |
| Harpenden Biltong Ltd | Hospitality | 2024 |
| Harpenden Blinds Limited | Extraterritorial | 2009 |
| Harpenden Boxing Club CIC | Arts & recreation | 2024 |
| Harpenden Car Sales Limited | Wholesale & retail | 2017 |
| Harpenden Carpentry and Upvc Services Limited | Construction | 2015 |
| Harpenden Common Golf Club Trading Limited | Hospitality | 2016 |
| Harpenden Computer Services Ltd | Administrative & support | 2012 |
| Harpenden Connect | Transport & logistics | 2016 |
| Harpenden Cricket Club | Arts & recreation | 2014 |
| Harpenden Curry Ltd | Hospitality | 2019 |
| Harpenden Cycles Limited | Wholesale & retail | 2013 |
| Harpenden Dental Centre Limited | Health & social care | 2015 |
| Harpenden Doggy Day Creche Ltd | Other services | 2019 |
| Harpenden Electrical Limited | Construction | 2006 |
| Harpenden Estates Limited | Construction | 1973 |
| Harpenden EYE and Medical Practitioners Ltd | Health & social care | 2024 |
| Harpenden Fitted Ltd | Construction | 2025 |
| Harpenden Food and Wine Ltd | Wholesale & retail | 2024 |
| Harpenden Golf Club Limited | Arts & recreation | 1965 |
| Harpenden Handyman Ltd | Construction | 2017 |
| Harpenden Health PCN Limited | Health & social care | 2022 |
| Harpenden Home Handyman Services Ltd | Construction | 2025 |
| Harpenden Home Maintenance Limited | Other services | 2022 |
| Harpenden House Limited | Hospitality | 2014 |
| Harpenden Lighting Design Company Ltd | Construction | 2020 |
| Harpenden Ltd | Extraterritorial | 2010 |
| Harpenden Medical Limited | Health & social care | 2024 |
| Harpenden Mencap | Health & social care | 1994 |
| Harpenden Mill Autocare Limited | Wholesale & retail | 2015 |
| Harpenden Osteopathy & Sports Injury Limited | Health & social care | 2012 |
| Harpenden Pizza Limited | Hospitality | 2018 |
| Harpenden Plumbing and Heating Limited | Construction | 2016 |
| Harpenden Property Maintenance Ltd | Professional & scientific | 2026 |
| Harpenden Rugby Football Club Limited | Arts & recreation | 2017 |
| Harpenden Secondary Education Trust | Education | 2014 |
| Harpenden Spice House Limited | Hospitality | 2024 |
| Harpenden Spice Ltd | Hospitality | 2019 |
| Harpenden Sports Ground,Limited(The) | Real estate | 1925 |
| Harpenden Sushi Ltd | Hospitality | 2017 |
| Harpenden Taxis Ltd. | Transport & logistics | 2000 |
| Harpenden Town Football Club Limited | Arts & recreation | 2007 |
| Harpenden Turkish Barber Ltd | Other services | 2017 |
| Harper & West Limited | Construction | 2011 |
| Harphill Ltd | Professional & scientific | 2011 |