| Hannah FRY Limited | Education | 2016 |
| Hannah Meur Design Limited | Professional & scientific | 2015 |
| Hannington Developments Ltd | Wholesale & retail | 2006 |
| Hansib Publications Limited | Administrative & support | 1997 |
| Hanuman Stevenage Limited | Hospitality | 2024 |
| Happy Daze Care Ltd | Health & social care | 2025 |
| Happy POM Poms Limited | Health & social care | 2022 |
| Happy PUB Group Ltd | Hospitality | 2025 |
| Harbour Homes Holdings Ltd | Financial services | 2020 |
| Harbour Homes UK Limited | Health & social care | 2007 |
| Harbour Living Solutions Ltd | Extraterritorial | 2014 |
| Hard Assets Ltd | Real estate | 2019 |
| Harding Advisory Partners Limited | Professional & scientific | 2025 |
| Hardware Garden & Pet Supplies Limited | Wholesale & retail | 1998 |
| Harkness Hall (Group) Limited | Information & communication | 1999 |
| Harkness Screens (Holdings) Limited | Information & communication | 2006 |
| Harkness Screens (UK) Limited | Information & communication | 1991 |
| Harkness Screens (USA) Limited | Information & communication | 1997 |
| Harlequin Design (London) Limited | Manufacturing | 2004 |
| Harlequin Fabrication Ltd | Professional & scientific | 2025 |
| Harlequin Open System Tools Limited | Extraterritorial | 2020 |
| Harlequin Workshops Limited | Manufacturing | 2014 |
| Harley Plumbing & Heating Ltd | Construction | 2026 |
| Harmer Green Ventures Ltd | Administrative & support | 2015 |
| Harmonica Holdings Limited | Arts & recreation | 2023 |
| Harmonica Mastery Limited | Arts & recreation | 2021 |
| Harnik Ltd | Health & social care | 2025 |
| Harrington PM Limited | Households | 2026 |
| Harrison Homes Commercial Limited | Construction | 2026 |
| Harrison Homes Developments Limited | Construction | 2015 |
| Harrison Turner Group Ltd | Construction | 2023 |
| Harrison's Plumbing & Heating Limited | Construction | 2018 |
| Harrison-Field Limited | Manufacturing | 1993 |
| Harrisons Wharf (Phase II) Management Company Limited | Households | 2001 |
| Harry's Seafood & Fish Limited | Hospitality | 2013 |
| Hartland Court (Management) Co.Limited | Households | 1972 |
| Hartlands Investments Ltd | Real estate | 2024 |
| Harts Consulting Partners Limited | Other services | 2017 |
| Harwood Park Crematorium (Management) Limited | Other services | 1993 |
| Harwood Park Crematorium Limited | Other services | 1988 |
| Harwood Park Holdings Limited | Financial services | 2018 |
| Haset Multisectors Ltd | Health & social care | 2024 |
| Haus Commercial Limited | Other services | 2017 |
| Hauxbourn Homes Ltd | Real estate | 2026 |
| Havelock Advisers Limited | Professional & scientific | 2015 |
| Haven First | Hospitality | 1997 |
| Haven Tax Service Limited | Professional & scientific | 1993 |
| Havenbrook Ltd | Hospitality | 2019 |
| Hawk KBF Ltd | Construction | 2023 |
| Hawkins Screeding Company Limited | Construction | 1999 |
| Hawkstone Builders Ltd | Construction | 2010 |
| Hawkwell Services Limited | Construction | 1999 |
| Hawthorn Land Limited | Real estate | 2018 |
| Haydenlang Limited | Construction | 1978 |
| Hayder & Co Ltd | Hospitality | 2020 |
| Hayer Partnerships Ltd | Other services | 2023 |
| Hayes VS Limited | Professional & scientific | 2017 |
| Haysi Ventures Limited | Information & communication | 2016 |
| Hayward Blanes Properties Limited | Real estate | 2017 |
| Hazelmere Stryd Properties Ltd | Real estate | 2026 |
| HC Cleaning Services Ltd | Administrative & support | 2020 |
| Head Cases (Europe) Limited | Manufacturing | 2010 |
| Head Cases (US) Limited | Manufacturing | 2013 |
| Head Clinic Limited | Administrative & support | 2011 |
| Head Concierge Limited | Administrative & support | 2003 |
| Headline Security Management Limited | Administrative & support | 1999 |
| Heads of Department Limited | Education | 2025 |
| Healhaus Ltd | Health & social care | 2026 |
| Health Cuts Limited | Arts & recreation | 2008 |
| Health Dimensions International Ltd | Health & social care | 2014 |
| Health Oasis Ltd | Health & social care | 2024 |
| Healthcare Professionals Across the Borders | Health & social care | 2021 |
| Healthcare Professionals Initiative UK Ltd | Education | 2023 |
| Healthcare Today Limited | Administrative & support | 2013 |
| Healthii People Group Ltd | Administrative & support | 2025 |
| Healthwatch Hertfordshire Limited | Health & social care | 2012 |
| Healthwatch Hertfordshire Trading Limited | Health & social care | 2024 |
| Healthy Careers Limited | Administrative & support | 2025 |
| Healthy Innovations Limited | Administrative & support | 2026 |
| Healthy Smile Clinic Limited | Health & social care | 2021 |
| Healthy Wayz Limited | Health & social care | 2020 |
| Heanly Harris Limited | Professional & scientific | 2022 |
| Hearn Medical Ltd | Health & social care | 2025 |
| Hearts Services Herts Limited | Health & social care | 2011 |
| Heartview Windows Ltd | Construction | 2024 |
| Heartwood Welding Company Limited | Construction | 2013 |
| Heat Elite Limited | Construction | 2020 |
| Heath Cafe Bar Limited | Hospitality | 2018 |
| Heath Company Holdings Limited | Financial services | 2021 |
| Heather and Smoke Productions Ltd | Education | 2021 |
| Heather Isle Media Limited | Professional & scientific | 2026 |
| Heather Thompson Social Work Ltd | Health & social care | 2026 |
| Heating Helpers Limited | Construction | 2019 |
| Heatsafe Plumbing and Heating Ltd | Construction | 2014 |
| Heatstream Limited | Construction | 2015 |
| Heckford Norton LLP | | 2013 |
| Heckford Norton Services Limited | Extraterritorial | 2013 |
| Hecquet Enterprises Limited | Professional & scientific | 2020 |
| Hecquet Holdings Limited | Professional & scientific | 2025 |
| Hedgehog Books Ltd | Wholesale & retail | 2020 |