| Here WE Care Limited | Administrative & support | 2024 |
| Heritage Oak Group Limited | Real estate | 2025 |
| Heritage Trees Limited | Agriculture & fishing | 2014 |
| Hermes of Mayfair Ltd. | Wholesale & retail | 2015 |
| Hermiston Court Limited | Households | 1958 |
| Hermitage Designs Ltd | Real estate | 2013 |
| Heroes Global Venture Ltd | Other services | 2021 |
| Herons Football Club Limited | Arts & recreation | 2026 |
| Herren Ltd | Construction | 2015 |
| Hertford Decor Limited | Real estate | 1958 |
| Hertford END Court Limited | Households | 1999 |
| Hertford Investment Company Limited | Real estate | 1958 |
| Hertfordshire Bake House Limited | Hospitality | 2020 |
| Hertfordshire Construction Supplies Ltd | Real estate | 2023 |
| Hertfordshire Design & Planning Ltd | Professional & scientific | 2014 |
| Hertfordshire Electrical Services Ltd | Construction | 2022 |
| Hertfordshire Mind Trading Limited | Education | 2025 |
| Hertingford Limited | Extraterritorial | 2021 |
| Herts Art Club Ltd | Health & social care | 2025 |
| Herts Beds & Bucks Farmers Limited | Agriculture & fishing | 1998 |
| Herts Building Experts Limited | Construction | 2025 |
| Herts Cars Watford Ltd | Transport & logistics | 2024 |
| Herts Cleaning Angels Ltd | Households | 2017 |
| Herts Cleaning Services Ltd | Administrative & support | 2017 |
| Herts Design & Build Ltd | Construction | 2014 |
| Herts Floor Sanding & Fitting Ltd | Manufacturing | 2025 |
| Herts Flooring Solutions Ltd | Construction | 2025 |
| Herts Food & Wine Ltd | Wholesale & retail | 2020 |
| Herts Glass Windows and Doors Ltd | Other services | 2020 |
| Herts Haven Ltd | Real estate | 2024 |
| Herts Homeless Alliance Ltd | Hospitality | 2021 |
| Herts Mind Network | Health & social care | 2005 |
| Herts Prestige Autohaus Ltd | Wholesale & retail | 2025 |
| Herts Property Company Ltd. | Real estate | 2022 |
| Herts Property Experts Ltd | Real estate | 2026 |
| Herts Property Group Ltd | Real estate | 2024 |
| Herts Property Holdings Ltd. | Real estate | 2026 |
| Herts Smile LAB Ltd | Manufacturing | 2024 |
| Herts Soft Play Hire Ltd | Other services | 2023 |
| Hertsmere Living Limited | Real estate | 2022 |
| Hesmondhalgh Homes Limited | Real estate | 1981 |
| Hesston Ltd | Wholesale & retail | 2014 |
| Heward Property Company Limited | Real estate | 2020 |
| Hewfic | Financial services | 2023 |
| Hewn Space Ltd | Real estate | 2020 |
| HEX LAB Ltd | Manufacturing | 2026 |
| Hexabax UK Ltd | Professional & scientific | 2017 |
| Hexagon Acquisitions Ltd | Real estate | 2018 |
| Hexagon Letting Co Ltd | Real estate | 2012 |
| Hexair Systems Limited | Manufacturing | 2026 |
| HEY Insights Limited | Information & communication | 2025 |
| HEY Kitty KAT Ltd | Wholesale & retail | 2019 |
| Heymaa Limited | Hospitality | 2006 |
| Heymaa Partnership LLP | | 2006 |
| Heymaa Watford Limited | Hospitality | 1994 |
| Heyo Afro Foods Ltd | Wholesale & retail | 2023 |
| Heyo Limited | Construction | 2015 |
| HF Plumbing & Heating Ltd | Construction | 2020 |
| Hfcpbussiness Limited | Hospitality | 2024 |
| HFM Solutions Limited | Professional & scientific | 2011 |
| Hfrough Ltd | Households | 2025 |
| HGC Technologies UK Ltd | Wholesale & retail | 2020 |
| Hgcy Limited | Other services | 2017 |
| Hgrafters Ltd | Administrative & support | 2025 |
| Hgsj Properties Ltd | Real estate | 2018 |
| HH 2020 Limited | Administrative & support | 2020 |
| HHG Financial Services Ltd | Professional & scientific | 2018 |
| HHM Freehold Management Limited | Households | 2020 |
| Hi-Standard Builders Limited | Construction | 2011 |
| HIA Marketing Ltd | Professional & scientific | 2024 |
| HIA Media Ltd | Information & communication | 2024 |
| HIA Network Ltd | Financial services | 2018 |
| HIA Property Ltd | Real estate | 2020 |
| Hiba Noor Films Ltd | Professional & scientific | 2024 |
| Hibernia Developments Limited | | 2014 |
| HIC Treasury Limited | Professional & scientific | 1982 |
| Hickey Heating Services Limited | Construction | 2010 |
| Hietanen Consultancy Ltd | Information & communication | 2025 |
| Higgs, Harding and Allen Limited | Construction | 2018 |
| High Bridge Business Solutions Ltd | Professional & scientific | 2011 |
| High Bridge Property Management Ltd | Real estate | 2022 |
| High Cornerstone Projects Ltd | Construction | 2025 |
| High Cross Ventures 1 Limited | Financial services | 2025 |
| High Cross Ventures 2 Limited | Financial services | 2025 |
| High Cross Ventures Limited | Financial services | 2015 |
| High Elms Consulting Ltd. | Information & communication | 2011 |
| High Performance Contractors Ltd | Construction | 2024 |
| High ST Properties Ltd | Real estate | 2026 |
| High Voltage Substation Services Limited | Manufacturing | 2008 |
| Highbury Connect Limited | Information & communication | 2026 |
| Highend Accessories Ltd | Wholesale & retail | 2017 |
| Highfield SB Limited | Financial services | 2016 |
| Highgrove Planning Consultants Limited | Real estate | 2023 |
| Highland Mobile Trading Ltd | Wholesale & retail | 2023 |
| Highlands Properties Holdings Limited | Professional & scientific | 2008 |
| Highlight Developments Limited | Real estate | 2019 |
| Hight Ltd | Information & communication | 2017 |
| Highview Court RTM Company Limited | Households | 2010 |
| Highwood Financial Services Group Limited | Administrative & support | 2009 |
| Highwood Management Services Ltd | Administrative & support | 2009 |