| Group Seventeen Limited | Professional & scientific | 2025 |
| Group Y Limited | Professional & scientific | 2012 |
| Grow Better Limited | Professional & scientific | 2022 |
| Grow Brand Limited | Wholesale & retail | 2021 |
| Grow Chiswell Green Ltd | Arts & recreation | 2022 |
| Grow With Lucy Limited | Administrative & support | 2021 |
| Grsj Consulting Limited | Professional & scientific | 2017 |
| Gryphon Financial Management Limited | Professional & scientific | 2016 |
| Guest Marketing Limited | Professional & scientific | 2025 |
| GUI Design Collective Limited | Professional & scientific | 2024 |
| GW Risk Limited | Administrative & support | 2006 |
| Gwigu Ltd | Wholesale & retail | 2017 |
| Gworktops Limited | Construction | 2006 |
| GX Trade Limited | Transport & logistics | 2021 |
| Gym Bell Ltd | Other services | 2010 |
| Gymspiration Sports Mats Ltd | Wholesale & retail | 2014 |
| Gymtro Limited | Other services | 2017 |
| Gymtro ST Albans Ltd | Arts & recreation | 2022 |
| Gynaemedics Ltd | Health & social care | 2024 |
| Gynecomastia Medics UK Limited | Extraterritorial | 2020 |
| Gyoury Self Partnership (ST. Albans) LLP | | 2002 |
| Gyoury Self Partnership Consulting Engineers (ST Albans) Ltd | Professional & scientific | 2015 |
| H & G Property Ventures Limited | Real estate | 2019 |
| H & S Accounting Ltd | Professional & scientific | 2016 |
| H J Heating Services Limited | Construction | 2006 |
| H M Renovations Limited | Manufacturing | 2020 |
| H&Rb Properties Ltd | Real estate | 2020 |
| H. T. C. Fastenings Limited | Wholesale & retail | 1976 |
| H14 Energy Limited | Energy | 2014 |
| H2O Power Generation Ltd | Energy | 2014 |
| H6 Properties Limited | Real estate | 2020 |
| HAC Plant Hire Ltd | Administrative & support | 2005 |
| Hackett Equine Ltd | Arts & recreation | 2019 |
| Hackett Equine Online Ltd | Wholesale & retail | 2020 |
| Hackett Land Limited | Real estate | 2007 |
| Hackett Securities Limited | Real estate | 2007 |
| Hackwood Design Ltd | Professional & scientific | 2013 |
| Haddon & James Logistics Ltd | Other services | 2017 |
| Haddon & James Retail Limited | Other services | 2017 |
| Hadji Medical Group Ltd | Health & social care | 2024 |
| Haiders Capital Ltd | Financial services | 2017 |
| Hair Medical Products Limited | Other services | 2020 |
| Hair Medical UK (Chiswick) Limited | Other services | 2026 |
| Hair Medical UK Limited | Other services | 2018 |
| Haive Systems Ltd | Construction | 2017 |
| Hakka Express Kitchen Limited | Hospitality | 2023 |
| Halifield Land Trading Limited | Real estate | 2024 |
| Hallmark Consultants Ltd | Information & communication | 2012 |
| Halo Power Ltd | Energy | 2019 |
| Haloearth Limited | Information & communication | 2026 |
| Halogen Digital Limited | Other services | 2016 |
| Hamblin Sullivan Associates Ltd | Administrative & support | 2014 |
| Hamerton Enterprises (NO.1) Ltd | Construction | 2025 |
| Hamerton Enterprises Ltd | Construction | 2025 |
| Hamerton Installations Ltd | Construction | 2025 |
| Hamilton Performance Operations Ltd | Professional & scientific | 2025 |
| Hamish Hunter Ltd | Real estate | 2020 |
| Hammer Enterprises Ltd | Construction | 2025 |
| Hammersmatch Properties Limited | Construction | 1981 |
| Hammock Consultancy Ltd | Professional & scientific | 2025 |
| Hamps 52 Exhibition Limited | Transport & logistics | 2022 |
| Hampsfell Limited | Real estate | 2019 |
| Hampstead Consulting Ltd | Professional & scientific | 2013 |
| Hampstead Gymnastics Club C.I.C. | Education | 2022 |
| Hanburys Business Solutions Ltd | Professional & scientific | 2025 |
| Hand Rails R US Ltd | Information & communication | 2014 |
| Handley Page Limited | Extraterritorial | 2007 |
| Handy Floors Ltd | Administrative & support | 2023 |
| Hannah Hope Nutrition Ltd | Health & social care | 2006 |
| Hanoli Ltd | Professional & scientific | 2025 |
| Hanrahan Access Platform Specialists Limited | Administrative & support | 2019 |
| Hanrahan Group Limited | Administrative & support | 2023 |
| Hans Homes Limited | Real estate | 2026 |
| Hanse Haus Modular Limited | Construction | 2017 |
| Hanworth Contractors Ltd | Construction | 2014 |
| Happy Home Coaching Ltd | Education | 2015 |
| Happy Human Project Ltd | Education | 2022 |
| Happy Whale Limited | Administrative & support | 2009 |
| Happy Works Enterprises Ltd | Professional & scientific | 2015 |
| Happycrew Childcare Ltd | Health & social care | 2021 |
| Harabara Ltd | Hospitality | 2023 |
| Haraval Enterprises Ltd | Wholesale & retail | 2024 |
| Harbottle Trustee Company NO 1 Limited | Professional & scientific | 2017 |
| Harbottle Trustee Company NO 2 Limited | Professional & scientific | 2017 |
| Harbour Porsche Limited | Wholesale & retail | 2026 |
| Hard Advisory Service Ltd. | Financial services | 2012 |
| Hardenstance Limited | Information & communication | 2016 |
| Hardings Properties Limited | Real estate | 2020 |
| Harentor Limited | Wholesale & retail | 2020 |
| Harfi Limited | Wholesale & retail | 2018 |
| Harford Specialised Services Limited | Construction | 1989 |
| Hargrave Property Management Limited | Real estate | 2023 |
| Harlequin Windows and Doors Limited | Construction | 2011 |
| Haroon Global Limited | Real estate | 2016 |
| Harp Roofing Ltd | Construction | 2025 |
| HARPEN268 Ltd | Information & communication | 2022 |
| Harpenden Colts FC | Arts & recreation | 2016 |
| Harpenden Hawks Netball Ltd | Education | 2021 |
| Harpenden Heat Pumps Ltd | Construction | 2025 |
| Harpenden Road Limited | Financial services | 2022 |