| Hertfordshire & Middlesex Wildlife Trust Limited | Arts & recreation | 1964 |
| Hertfordshire Aesthetics Academy Limited | Education | 2023 |
| Hertfordshire Aesthetics Limited | Health & social care | 2023 |
| Hertfordshire Community Kitchen CIC | Education | 2023 |
| Hertfordshire Funeral Service Limited | Extraterritorial | 2002 |
| Hertfordshire Overnight Limited | Transport & logistics | 1997 |
| Hertfordshire Resin Specialists Ltd | Construction | 2025 |
| Hertfordshire Sound and Light Ltd | Arts & recreation | 2022 |
| Hertfordshire Sports Holdings Limited | Professional & scientific | 2011 |
| Hertfordshire Tiny Tats & Piercing Limited | Other services | 2023 |
| Hertfordshire Vehicle Storage Limited | Transport & logistics | 2018 |
| Hertfordshirehouseclearance Limited | Transport & logistics | 2024 |
| Herts Airports Taxis Ltd | Transport & logistics | 2024 |
| Herts Bespoke Ltd | Wholesale & retail | 2025 |
| Herts Care Staff Ltd | Administrative & support | 2017 |
| Herts Cleaning and Maintenance Ltd | Administrative & support | 2026 |
| Herts Couriers Services Limited | Transport & logistics | 2022 |
| Herts Cupping Ltd | Health & social care | 2023 |
| Herts Dermatology Ltd | Health & social care | 2025 |
| Herts Direct Cremations Ltd | Other services | 2022 |
| Herts Fencing Contractors Ltd | Construction | 2025 |
| Herts Groundworks and Civils Ltd | Construction | 2026 |
| Herts Gynae Limited | Extraterritorial | 2011 |
| Herts Homes Ltd | Real estate | 2011 |
| Herts Marketing Specialist Ltd | Wholesale & retail | 2026 |
| Herts Master Locksmith Ltd | Other services | 2023 |
| Herts Osteopathy Limited | Health & social care | 2018 |
| Herts PCI CIC | Other services | 2016 |
| Herts Property Developments Ltd | Construction | 2022 |
| Herts Radiology Limited | Health & social care | 2014 |
| Herts Renewable Energy Solutions Ltd | Energy | 2015 |
| Herts Resin Ltd | Construction | 2023 |
| Herts Special Vehicles Limited | Wholesale & retail | 2024 |
| Herts Sticker Club Ltd | Wholesale & retail | 2026 |
| Herts Tints Ltd | Professional & scientific | 2012 |
| Herts Wellness Ltd | Other services | 2026 |
| Hesketh (ST. Albans) Limited | Real estate | 2009 |
| Hesketh Homes (Herts) Limited | Construction | 2014 |
| Heti's Colours Limited | Professional & scientific | 2011 |
| Heverin Haulage Limited | Water & waste | 1998 |
| Hewitt Stone Limited | Wholesale & retail | 2012 |
| Hewlett Packard Enterprise UK Pension Trustee Limited | Other services | 2016 |
| Hexagon Management Limited | Professional & scientific | 1992 |
| Hexzagon New Homes Limited | Financial services | 2015 |
| Heydon & Carr Limited | Construction | 2007 |
| Heydon Holdings Limited | Financial services | 2017 |
| Heydon Investments Limited | Real estate | 2018 |
| HG Land & Property Ltd | Construction | 2023 |
| HGS Media Limited | Professional & scientific | 2014 |
| HH Talent Limited | Administrative & support | 2021 |
| Hhsp Ltd | Construction | 2022 |
| HHV Property Ltd | Extraterritorial | 2023 |
| HHZ11 Limited | Professional & scientific | 2021 |
| Hi-Fi City Limited | Wholesale & retail | 1990 |
| Hi-Pro Sports Limited | Wholesale & retail | 1996 |
| Hicks Consulting Services Ltd | Professional & scientific | 2020 |
| Hidden Beauty by Catherine Costas Ltd | Other services | 2021 |
| Higem Limited | Financial services | 2014 |
| High Elms Tree Surgery Limited | Agriculture & fishing | 2004 |
| High END Goods Ltd | Wholesale & retail | 2019 |
| High Oaks 1964 Limited | Extraterritorial | 2014 |
| High ST W5 Holdco Limited | Financial services | 2026 |
| High Street Imports Ltd | Wholesale & retail | 2024 |
| Highacre, 1 Old Park Road, Management Company Limited | Households | 1991 |
| Higher Arcade Ltd | Extraterritorial | 2024 |
| Highfield Commercial Cleaning Services Ltd | Administrative & support | 2026 |
| Highfield Hall Management Company Limited | Households | 1989 |
| Highfield Park Trust | Arts & recreation | 1996 |
| Hill Mcmanus Limited | Education | 2008 |
| Hillbury Consulting Ltd | Professional & scientific | 2026 |
| Hillhouse Integrated Services Ltd | Information & communication | 2026 |
| Hillmorton Financial Services Limited | Financial services | 2001 |
| Hills Yard Mews Management Company Limited | Households | 2016 |
| Hillside Garden Limited | Hospitality | 2019 |
| Hillside Power Development Ltd | Professional & scientific | 2025 |
| Hippo Components Limited | Wholesale & retail | 2017 |
| Hire Online Ltd | Information & communication | 2019 |
| Historyriot Ltd | Education | 2021 |
| HITCHIN(516) DCL Ltd | Real estate | 2016 |
| HITCHIN(516A) DCL Ltd | Real estate | 2016 |
| Hive Financial Limited | Professional & scientific | 2024 |
| Hive Medical Ltd | Health & social care | 2021 |
| HJC Digital Ltd | Professional & scientific | 2021 |
| HJG Investments Limited | Real estate | 2022 |
| HLG Marketing Ltd | Professional & scientific | 2026 |
| HMC Property Group Acquisitions Ltd | Real estate | 2025 |
| HMC Property Group Ltd | Real estate | 2022 |
| HO, Brennan & Associates (UK) Limited | Real estate | 2018 |
| Hobbco Tools Limited | Wholesale & retail | 2018 |
| Hobby Republik Ltd | Administrative & support | 2023 |
| Hocking Technology Partners Ltd | Information & communication | 2024 |
| Hodden Grey Ltd | Administrative & support | 2025 |
| Hodge & Co. Ltd. | Professional & scientific | 2012 |
| Hoenle UV UK Ltd | Wholesale & retail | 2003 |
| HOL Consultants Ltd | Extraterritorial | 2021 |
| Holden Facilities Limited | Construction | 2022 |
| Holding Homes Ltd | Real estate | 2024 |
| HOLIDAYLETS4U Ltd | Real estate | 2026 |
| Holiving Ltd | Information & communication | 2021 |
| Holland Fresh Food Limited | Hospitality | 2024 |