| Hcdb Holdings Limited | Construction | 2025 |
| Hcdb Property Limited | Real estate | 2026 |
| HD Consulting Services Limited | Professional & scientific | 2021 |
| HD Productions Limited | Information & communication | 2013 |
| HD Spine Limited | Health & social care | 2022 |
| HD Watford Ltd | Wholesale & retail | 2022 |
| HD Wholesale Ltd | Wholesale & retail | 2026 |
| HDA Demolition & Plant Hire Limited | Construction | 2015 |
| Hdal Limited | Wholesale & retail | 2019 |
| HDS Public Service Ltd | Construction | 2022 |
| Heal Fast Limited | Public administration | 2025 |
| Health & Safety Consultants & Advisors Limited | Administrative & support | 2008 |
| Health House Pharma Limited | Wholesale & retail | 2019 |
| Health Outcomes Solutions Limited | Professional & scientific | 2008 |
| Healthable Ltd | Wholesale & retail | 2023 |
| Healthcare on the Go Ltd | Health & social care | 2022 |
| Healthcare-It Ltd | Information & communication | 2024 |
| Healthrx Group Limited | Wholesale & retail | 2023 |
| Healthy Bites Living Ltd | Hospitality | 2021 |
| Healthy Heel Ltd | Public administration | 2025 |
| Healthy Living (UK) Limited | Health & social care | 2017 |
| Healthy Smiles by Hardev Seehra Limited | Health & social care | 2021 |
| Hearn Engineering Limited | Professional & scientific | 2014 |
| Heartmender Limited | Health & social care | 2022 |
| Heartqbed Ltd | Health & social care | 2025 |
| Heartwood ASH Limited | Construction | 2015 |
| Heath Cleaning Ltd | Administrative & support | 2020 |
| Heath Design & Build Ltd | Construction | 2020 |
| Heath END Ventures Limited | Construction | 2001 |
| Heath Park House Residents Company Limited | Households | 2004 |
| Heath Surveys Limited | Construction | 2008 |
| Heathbuild Limited | Information & communication | 2015 |
| Heathcroft 2002 Limited | Households | 2002 |
| Heather and Rose Health Limited | Wholesale & retail | 2019 |
| Heathfield Close Management Company Limited | Households | 2019 |
| Heathfield Consulting Limited | Professional & scientific | 2007 |
| Heathfield Court (St.Albans) Management Co. Ltd | Households | 1987 |
| Heatsafe Solutions Ltd | Construction | 2020 |
| Heatx Ltd | Construction | 2018 |
| Heavenly Desserts Watford Limited | Hospitality | 2025 |
| Heavenly Dreamwear Ltd | Wholesale & retail | 2020 |
| Heavens Flowers Ltd | Wholesale & retail | 2019 |
| Hecate Bidco Limited | Financial services | 2021 |
| Hecate Cleanco Limited | Financial services | 2021 |
| Hecate Consulting Ltd | Professional & scientific | 2024 |
| Hecate Holdco Limited | Financial services | 2021 |
| Hecla Consulting Ltd | Information & communication | 2020 |
| Hectic Shoot Limited | Information & communication | 1997 |
| Hedgerow Group Limited | Administrative & support | 1999 |
| Hedu Consulting Ltd | Professional & scientific | 2019 |
| Heel Harmony Ltd | Health & social care | 2024 |
| Heene Road Veterinary Practice Limited | Professional & scientific | 2003 |
| Heer International Ltd | Wholesale & retail | 2025 |
| Heera Engineering Limited | Professional & scientific | 2017 |
| Hegde Imaging Solutions Ltd | Health & social care | 2024 |
| Heidelberg Consulting Limited | Professional & scientific | 2021 |
| Heidic Growth & Go Limited | Wholesale & retail | 2023 |
| Height and Hustle Limited | Professional & scientific | 2026 |
| Heirloomjewells Limited | Wholesale & retail | 2021 |
| Heirlooms of Tomorrow Ltd | Wholesale & retail | 2025 |
| Heksh Limited | Wholesale & retail | 2015 |
| Helembyn Ltd | Construction | 2024 |
| Helen Exley Creative Limited | Arts & recreation | 2010 |
| Helex Healthcare UK Ltd | Wholesale & retail | 2026 |
| Helio Holdings Limited | Financial services | 1997 |
| Hellolithuania C.I.C. | Health & social care | 2025 |
| Helloshine Ltd | Administrative & support | 2022 |
| Hellstrom IT Ltd | Information & communication | 2019 |
| Helms Holdings Ltd | Professional & scientific | 2023 |
| Helola Services LLP | | 2025 |
| HELP2ASPIRE CIC | Health & social care | 2022 |
| Helping Hands Supported Living CIC | Health & social care | 2023 |
| Helping Hands Watford Ltd | Health & social care | 2009 |
| Hemel Optics Limited | Health & social care | 2012 |
| Hemel Tamil Association | Education | 2016 |
| Hemp Biologix Limited | Professional & scientific | 2017 |
| Hemsons UK Limited | Professional & scientific | 2018 |
| Hench West Watford Ltd | Hospitality | 2025 |
| Henco Heating Limited | Construction | 2000 |
| Henderson Bond Limited | Administrative & support | 2018 |
| Heni Global Ltd | Wholesale & retail | 2025 |
| Hennessy Worldwide Ltd | Information & communication | 2022 |
| Hennumi Ltd | Manufacturing | 2016 |
| Henriks Recovery Ltd | Transport & logistics | 2025 |
| Henry Construction Limited | Construction | 1973 |
| Henry Finance Ltd | Administrative & support | 2021 |
| Henry Fraser Enterprises Limited | Arts & recreation | 2018 |
| Henry Fraser Limited | Education | 2016 |
| Henry Investments Limited | Administrative & support | 2011 |
| Hensure Limited | Construction | 2020 |
| Henwell Properties Limited | Real estate | 2000 |
| Heor Consult Ltd | Professional & scientific | 2019 |
| HEP System Software Solutions Ltd | Information & communication | 2017 |
| Hepta Global Limited | Administrative & support | 2012 |
| HER Bloom Room Ltd | Wholesale & retail | 2026 |
| Hera Housing Ltd | Real estate | 2025 |
| Heracles Financial Services Ltd | Professional & scientific | 2021 |
| Herbal Health Ceylon UK Ltd | Health & social care | 2025 |
| Herbert Oconnor Ltd | Real estate | 2026 |
| Here 2 Build London Ltd | Construction | 2025 |