| Harpenden Wills Limited | Professional & scientific | 2018 |
| Harpenden Window Company Limited | Construction | 1986 |
| Harrall Care Services Limited | Health & social care | 2009 |
| Harriet Fleming Surveyors Ltd | Other services | 2019 |
| Harrigson Limited | Manufacturing | 2024 |
| Harris Begley Lifetime Partners Limited | Financial services | 2003 |
| Harry Needham Limited | Professional & scientific | 2021 |
| Harry&Alvin Properties Limited | Real estate | 2021 |
| Hartline Limited | Information & communication | 2023 |
| Harvec Limited | Wholesale & retail | 2020 |
| Harvest of Grace CIC | Hospitality | 2025 |
| Hashtagjustbecausegifts Limited | Wholesale & retail | 2022 |
| Hatch END R&Mc Energy Ltd. | Manufacturing | 2017 |
| Hatfield Care Ltd | Health & social care | 2018 |
| Hattron Investments Limited | Financial services | 2024 |
| Haulers Hub Ltd | Transport & logistics | 2023 |
| Haus of Vanity Ltd | Other services | 2010 |
| Haven Spirits Ltd | Wholesale & retail | 2020 |
| Havewell Construction Ltd | Construction | 2017 |
| Hawa Multicultural Services CIC | Health & social care | 2022 |
| Hawk Ventures Limited | Construction | 2002 |
| Hawker Trading Limited | Administrative & support | 1997 |
| Hayaah Group Ltd | Hospitality | 2021 |
| Haydn Scenery Limited | Construction | 2025 |
| Hayes Carpentry Limited | Construction | 2021 |
| Haylock Estates Ltd | Real estate | 2025 |
| Hayter Builders Limited | Construction | 2013 |
| Haywire Industries Ltd. | Arts & recreation | 2016 |
| Hazels ST Albans Ltd | Hospitality | 2024 |
| Hazelwood Investment Group Limited | Real estate | 2025 |
| Hazlewoodbuild Ltd | Construction | 2025 |
| HBB Financial Limited | Financial services | 2007 |
| HBF Ventures Ltd | Hospitality | 2025 |
| HCE Consulting Ltd | Professional & scientific | 2026 |
| HCG 1 Ltd | Wholesale & retail | 2025 |
| Hcvc Anello SPV 2021 LLP | | 2021 |
| Hcvc GIRAFFE360 SPV 2021 LLP | | 2021 |
| Hcwc Pilates Ltd | Arts & recreation | 2022 |
| HD Plastics Limited | Manufacturing | 2025 |
| Head's UP Hair Home(H.U.H.H) Limited | Other services | 2014 |
| Headline Event Management Limited | Administrative & support | 1996 |
| Headliner Collective Ltd | Professional & scientific | 2026 |
| Heads in Herts Ltd | Health & social care | 2025 |
| Headway Recruitment Services Limited | Administrative & support | 2009 |
| Healing Jesus Crusade | Other services | 2016 |
| Health LAB Group Ltd | Health & social care | 2025 |
| Health Matas Limited | Professional & scientific | 2024 |
| Healthcare Governance Ltd | Other services | 2014 |
| Healthicity Ltd | Health & social care | 2022 |
| Healthpharma Solutions Ltd | Professional & scientific | 2024 |
| Healthtech Ventures LLP | | 2021 |
| Healthy Grill House Ltd | Hospitality | 2025 |
| Hearing Direct International Limited | Wholesale & retail | 2021 |
| Heartcooked Holdings Limited | Financial services | 2025 |
| Heartwood Accountants Limited | Professional & scientific | 2021 |
| Heartwood Garden Design Ltd | Administrative & support | 2022 |
| Heartwood Group Ltd | Real estate | 2019 |
| Heartwood Secretarial Services Ltd | Administrative & support | 2022 |
| Heartwood Shutters Limited | Construction | 2015 |
| Heartwood Tea Rooms Ltd | Hospitality | 2023 |
| Heath Lodge Veterinary Services Limited | Professional & scientific | 2001 |
| Heather Trefusis Art Ltd | Manufacturing | 2021 |
| Heatherwood (Yiewsley) Management Company Limited | Administrative & support | 1988 |
| Heathfield Advisory Ltd | Professional & scientific | 2023 |
| Heatrite Plumbing and Heating Ltd | Construction | 2023 |
| Heaven IS a Cupcake Ltd | Hospitality | 2015 |
| Hedge Lake Ltd | Financial services | 2026 |
| Hedizaju Ltd | Financial services | 2010 |
| Helen Ashley Limited | Arts & recreation | 2008 |
| Helen Wright Coaching Ltd | Administrative & support | 2024 |
| Helena Howbury Limited | Real estate | 2005 |
| Helium Engineering Limited | Professional & scientific | 2017 |
| Helix One Ltd | Information & communication | 2026 |
| Hellenic Dynamics PLC | Professional & scientific | 2007 |
| Hello Lucky Limited | Wholesale & retail | 2024 |
| Hellonext (UK) Limited | Transport & logistics | 2013 |
| Helping People Succeed Ltd | Professional & scientific | 2017 |
| Hemstrom Limited | Wholesale & retail | 2024 |
| HEN Kinz Ltd | Hospitality | 2025 |
| Henarch Galleries Fine Art Limited | Wholesale & retail | 2019 |
| Heng Corp Ltd | Real estate | 2022 |
| Henmid Ltd | Health & social care | 2012 |
| Henne's Pet Shop Ltd | Wholesale & retail | 2025 |
| Henno Finishes Limited | Professional & scientific | 2011 |
| Henrietta Flood Ltd | Professional & scientific | 2016 |
| Heola Limited | Administrative & support | 2015 |
| Hera Wellbeing Collective CIC | Health & social care | 2023 |
| Herbscape CIC | Agriculture & fishing | 2023 |
| Hercules Events Limited | Arts & recreation | 2011 |
| Hercules Professional Services Ltd | Information & communication | 2016 |
| Hercules Properties Limited | Real estate | 2020 |
| Herga Court Watford Ltd | Households | 2002 |
| Heritage Design Projects Limited | Manufacturing | 2006 |
| Herkomer SET Services Ltd | Information & communication | 2025 |
| Hermes Pension Trustees Limited | Administrative & support | 2008 |
| Heron Close Management Company Limited | Households | 2014 |
| Hers N Sirs Hair Limited | Other services | 2003 |
| Hertford Corn Exchange Ltd | Hospitality | 2025 |
| Hertford Counselling Service Limited | Health & social care | 2014 |
| Hertford Mechanical Limited | Construction | 2013 |