| Harex Group Limited | Professional & scientific | 2024 |
| Harolie Ltd | Health & social care | 2020 |
| Harpenden Maths LLP | | 2026 |
| Harper AMY Ltd | Professional & scientific | 2023 |
| Harpers Event Staff Ltd | Hospitality | 2024 |
| Harriet Kelsall Jewellery Design Trustees Limited | Other services | 2025 |
| Harris Building Contractors Limited | Construction | 2014 |
| Harrpro Limited | Real estate | 2016 |
| Harry Larkin Limited | Information & communication | 2018 |
| Harwood Education Ltd | Education | 2018 |
| Hasbilalsum Limited | Real estate | 2021 |
| Hatfield Park Homes Limited | Construction | 2020 |
| Hausu London Ltd | Hospitality | 2023 |
| Hawk Medical Technologies Ltd | Wholesale & retail | 2021 |
| Hawkes Electrical Herts Limited | Construction | 2018 |
| Hawkins Development Projects Ltd | Construction | 2022 |
| Hawkins(Clothiers)Limited | Wholesale & retail | 1955 |
| Hayden Wealth Ltd | Professional & scientific | 2018 |
| Haynes & Haynes Ltd | Professional & scientific | 2023 |
| Haywood Equestrian Limited | Administrative & support | 2004 |
| Hazel Avenue Ltd | Real estate | 2026 |
| Hazelwood Securities Limited | Financial services | 2002 |
| HBL Homes Ltd | Real estate | 2023 |
| HBP Hairdressing Academy Ltd | Education | 2025 |
| HD Refinails Limited | Manufacturing | 2026 |
| HDA Auto Services Limited | Wholesale & retail | 2015 |
| HDA Network Properties Limited | Real estate | 2024 |
| HDT London Limited | Professional & scientific | 2022 |
| Head Services Ltd | Wholesale & retail | 2022 |
| Headcount Payroll Services Limited | Administrative & support | 2025 |
| Headway Hertfordshire Limited | Health & social care | 2001 |
| Heale's Clinics LLP | | 2001 |
| Heales Business Services Ltd | Administrative & support | 1999 |
| Heales Enterprises Ltd. | Information & communication | 2000 |
| Heales Health Services Ltd. | Health & social care | 2005 |
| Heales Innovation Limited | Health & social care | 2005 |
| Heales Medical CIC | Health & social care | 2026 |
| Heales Wellness Ltd. | Health & social care | 2005 |
| Health by Holly Ltd | Health & social care | 2025 |
| Heaps Thirsty Ltd | Financial services | 2024 |
| Hear & There Ltd | Health & social care | 2025 |
| Hearsave Limited | Wholesale & retail | 2015 |
| Heath Cars Ltd | Wholesale & retail | 2019 |
| Heathbush Limited | Construction | 1981 |
| Heather Morgan Property Limited | Real estate | 2026 |
| Heathmount International Limited | Administrative & support | 2000 |
| Heathrow Community Engagement Board Limited | Other services | 2018 |
| Hedgeplace Limited | Households | 1995 |
| Hedley & Weller Ltd | Financial services | 2017 |
| Heliconia Resorts Ltd | Real estate | 2018 |
| Helicopter Sharing Limited | Other services | 2011 |
| Helping Herts Homeless | Health & social care | 1997 |
| Hemingford Lodge (ST Ives) Ltd | Real estate | 2010 |
| Henderson's Property Investments Limited | Real estate | 2021 |
| Henlow Building Supplies Limited | Construction | 1981 |
| Henlow Lakes & Riverside Limited | Arts & recreation | 1989 |
| Henrymichaelgroup Limited | Administrative & support | 2026 |
| Herbert Maintenance Limited | Administrative & support | 2013 |
| Heritage Building Company Limited | Construction | 2021 |
| Heritage Land & Property Overseas Limited | Extraterritorial | 2010 |
| Heritage Lime Rendering Limited | Construction | 2026 |
| Heritage Slimline Limited | Construction | 2024 |
| Hermitage Services Management Limited | Professional & scientific | 2026 |
| Heroprops Ltd | Information & communication | 2023 |
| Hertfordshire Building Services Ltd | Construction | 2024 |
| Hertfordshire Carpentry Ltd | Construction | 2023 |
| Hertfordshire Construction Ltd | Construction | 2013 |
| Hertfordshire Drives and Landscapes Ltd | Construction | 2021 |
| Hertfordshire Property Solutions Limited | Construction | 2015 |
| Herts & Essex Financial Services Limited | Financial services | 2017 |
| Herts Cleaning Company Ltd | Administrative & support | 2025 |
| Herts Enviro Services Ltd | Water & waste | 2017 |
| Herts Hearing Limited | Wholesale & retail | 2019 |
| Herts Heating and Plumbing Services Ltd | Construction | 2022 |
| Herts Plumbing Limited | Construction | 2012 |
| Herts Surveying Limited | Other services | 2022 |
| HES Training Limited | Education | 2025 |
| Hesleyside Enterprises Limited | Education | 2006 |
| Hestia Consultants Ltd | Professional & scientific | 2025 |
| HET EOT Limited | Extraterritorial | 2025 |
| Heuston Enterprises Limited | Wholesale & retail | 1997 |
| Hewitt Day Limited | Construction | 2006 |
| Hewitt Heritage Investments Limited | Financial services | 2025 |
| HEX TEC Ltd | Manufacturing | 2011 |
| Hexagon Apartments Management Company Limited | Real estate | 2015 |
| Hexagon Wellness Ltd | Administrative & support | 2017 |
| Hexton Origins Ltd | Hospitality | 2023 |
| HF People Development Ltd | Professional & scientific | 2020 |
| HFR Management Limited | Professional & scientific | 2024 |
| HG Developments Limited | Financial services | 2011 |
| HG Drylining Limited | Construction | 2017 |
| HG Group (Holdings) Limited | Professional & scientific | 2020 |
| HG Homes Limited | Construction | 2025 |
| HG Living Limited | Construction | 2021 |
| HG M & E Limited | Construction | 2017 |
| HG Mercury Limited | Financial services | 2016 |
| HG Offsite Systems Ltd | Manufacturing | 2022 |
| HG Roofing Limited | Construction | 2025 |
| HG Vision Limited | Professional & scientific | 2026 |
| HGD Egham Limited | Construction | 2020 |