| HMM Effects Ltd | Professional & scientific | 2026 |
| Hmnm Ltd | Financial services | 2023 |
| HMO Trading Limited | Wholesale & retail | 2024 |
| HMX Trading Limited | Wholesale & retail | 2026 |
| HNC Consulting Engineers Ltd | Professional & scientific | 2024 |
| HNJ Enterprises Ltd | Construction | 2025 |
| HNJ Retail Ltd | Wholesale & retail | 2024 |
| HNJ Supermarket Ltd | Wholesale & retail | 2022 |
| Hnmh Investments Limited | Professional & scientific | 2025 |
| HNR Limited | Wholesale & retail | 2006 |
| HNS Cars Ltd | Wholesale & retail | 2022 |
| HNS Solutions Ltd | Professional & scientific | 2021 |
| Hocroft Court Management Limited | Households | 2009 |
| Hodacha Kumpalume Limited | Other services | 2015 |
| Hodari Property Ltd | Real estate | 2023 |
| Hoffman Quarry Limited | Real estate | 2003 |
| Hogg Physio Limited | Health & social care | 2025 |
| Hoggan HR Services Ltd | Administrative & support | 2014 |
| Hoist & FIX Rigging Ltd | Construction | 2024 |
| Hoiyiu Ltd | Wholesale & retail | 2024 |
| Hola Cars Ltd | Wholesale & retail | 2020 |
| Hola Nova Ltd | Administrative & support | 2026 |
| Holdblisk LP | | 2017 |
| Holden Road Management Company Limited | Real estate | 1988 |
| Holdtones Ltd | Information & communication | 2024 |
| Holistic Rejuvenation Ltd | Health & social care | 2017 |
| Holistic Safety Business Limited | Professional & scientific | 2017 |
| Holland Home Energy Services Limited | Construction | 2009 |
| Hollies END 007 Ltd | Financial services | 2018 |
| Hollingsworth Mews (Watford) NO.2 Management Limited | Households | 2020 |
| Holloway Construction Limited | Construction | 2010 |
| Holly Bear Consulting Ltd | Professional & scientific | 2024 |
| Holly Small Design Limited | Information & communication | 2008 |
| Holly Smiles Ltd | Health & social care | 2023 |
| Hollygrove Gardens Management Limited | Households | 2022 |
| Hollywoodn'T Limited | Information & communication | 1994 |
| Holm Oak Park Management (Watford) Limited | Real estate | 1990 |
| Holmbury Taverns Limited | Hospitality | 2020 |
| Holme Road Storage Ltd | Transport & logistics | 2021 |
| Holmes Management (ST. Albans) Limited | Households | 1978 |
| Holmwood Residential Investments Ltd | Real estate | 2023 |
| Holosguard Business Solutions Ltd | Extraterritorial | 2011 |
| Holyrood Court Apartments Limited | Households | 2008 |
| Holyrood Court Management Limited | Households | 1985 |
| Home & Garden Building & Design Limited | Construction | 2021 |
| Home & Healthstuff Limited | Wholesale & retail | 2019 |
| Home Comfort Assured Ltd. | Construction | 2013 |
| Home Comfort Design and Build London Ltd | Construction | 2023 |
| Home Counties Properties Limited | Real estate | 2001 |
| Home Interiors by IBT Ltd | Construction | 2018 |
| Home Pizza Ltd | Hospitality | 2025 |
| Home Property Inventories Ltd. | Other services | 2009 |
| Home-Start Watford and Three Rivers | Health & social care | 2005 |
| Homecure Limited | Construction | 2009 |
| Homefresh Property Services Ltd | Administrative & support | 2025 |
| Homelysource Ltd | Wholesale & retail | 2025 |
| Homes and Manors Ltd | Real estate | 2016 |
| Homeserve Solutions Group Ltd | Construction | 2026 |
| Homeserve-Uk Ltd | Construction | 2025 |
| Homespacesoluions Limited | Construction | 2010 |
| Homestruct Limited | Construction | 2025 |
| Hometown Haulers Ltd | Transport & logistics | 2025 |
| Homigramz Ltd | Wholesale & retail | 2025 |
| Honey Bunch Childcarers Ltd | Health & social care | 2015 |
| Honey Hill Construction Limited | Administrative & support | 2019 |
| Honeyman IT Consulting Ltd | Information & communication | 2008 |
| Honore Enterprises Ltd | Information & communication | 2009 |
| Hoolo Ltd | Information & communication | 2025 |
| Hoopdog Ltd | Construction | 2016 |
| Hope Creativity & Consultancy Ltd | Arts & recreation | 2016 |
| Hope Green Management Company Limited | Real estate | 2005 |
| Hopefit Ltd | Health & social care | 2023 |
| Hopsova Electrical Ltd | Construction | 2026 |
| Horizon Consultancy Services PVT Ltd | Information & communication | 2015 |
| Horizon IT Security & Services Ltd | Information & communication | 2018 |
| Horizons Capital Ltd | Construction | 2022 |
| Horizons Property Investment Ltd | Real estate | 2022 |
| Horn Lane Management Limited | Households | 2011 |
| Hornet Enterprises Limited | Professional & scientific | 2016 |
| Hornets Care Agency Ltd | Health & social care | 2016 |
| Hornhill Ltd | Wholesale & retail | 2021 |
| Horsehaven AP Properties Ltd | Households | 2022 |
| Horseshoe Lane (Garston) Caterers Limited | Hospitality | 1968 |
| Horticultural Coir Ltd. | Wholesale & retail | 1993 |
| HOS HQ Limited | Information & communication | 2026 |
| Hoschil LLP | | 2024 |
| Hosierydirect Ltd | Administrative & support | 2017 |
| Hospicode Direct UK Limited | Manufacturing | 2016 |
| Hospop Construction Ltd | Construction | 2024 |
| Host - IT Limited | Information & communication | 2012 |
| Host Milwaukee Ltd | Wholesale & retail | 2025 |
| Hosted Homes Ltd | Real estate | 2024 |
| Hot Express Watford Ltd | Hospitality | 2023 |
| Hot PIE Property Ltd | Real estate | 2020 |
| Hot Wheels Limited | Wholesale & retail | 2025 |
| Hot-Offer Ltd | Information & communication | 2012 |
| Hotel Puppy Limited | Other services | 2017 |
| Hoti Builders Ltd | Construction | 2018 |
| Hough Property Solutions Ltd | Construction | 2023 |
| House Equity Funding Limited | Financial services | 1994 |