| Herts Vehicle Solutions Ltd | Wholesale & retail | 2023 |
| Hesd DM 1 Ltd | Energy | 2024 |
| Hessa's Homeless Hounds C.I.C. | Health & social care | 2023 |
| HIB Engineering Ltd | Professional & scientific | 2026 |
| High Cross Service Station Limited | Wholesale & retail | 2016 |
| High Gale Law Limited | Financial services | 2016 |
| High Oak Business Centres (Hertford) Limited | Education | 2017 |
| High Oak Business Centres Limited | Financial services | 2007 |
| High Oak Enterprises Limited | Real estate | 2009 |
| High Oak Ventures Limited | Other services | 2026 |
| Highmill Management Company Limited(The) | Households | 1968 |
| Hillside Capital Partners Limited | Real estate | 2024 |
| Hilton Angling Ltd | Manufacturing | 2008 |
| Hind Property Group Ltd | Real estate | 2025 |
| Hind Quarters Polo Ltd | Arts & recreation | 2024 |
| Hirschfield Software Limited | Information & communication | 2021 |
| HLE Plumbing and Heating Ltd | Construction | 2023 |
| Hlsm Holdings Ltd | Real estate | 2024 |
| Hoddesdon Taxis Ltd | Transport & logistics | 2024 |
| Hodgson & Hart Ltd | Financial services | 2018 |
| Holdbrook Consult Ltd | Administrative & support | 2026 |
| Holland Heating Ltd | Construction | 2022 |
| Hollister Homes Ltd | Construction | 2021 |
| Hollister Property Coaching Ltd | Education | 2025 |
| Hollyhock Limited | Agriculture & fishing | 1990 |
| Hollywood Film Company UK Limited | Professional & scientific | 2026 |
| Holt Interests Ltd. | Real estate | 1998 |
| Holts Abattoir Ltd | Manufacturing | 2018 |
| Holtswatch Limited | | 1977 |
| Home and Garden Builders Limited | Construction | 2021 |
| Home Counties Asbestos Ltd | Professional & scientific | 2018 |
| Home Counties Golf & Leisure Limited | Construction | 2003 |
| Home Counties Haulage Ltd | Transport & logistics | 2012 |
| Home Farm Developments Limited | Construction | 1986 |
| Homeley Ltd | Real estate | 2023 |
| Homes BB Limited | Real estate | 2022 |
| Homeshield Windows & Cladding Ltd | Construction | 2013 |
| Honest Plumbing Co Ltd | Construction | 2022 |
| Hooked UP Cranes Ltd | Manufacturing | 2025 |
| Hornets Enterprises Limited | Financial services | 2016 |
| Horslen Sturge Property Investment Ltd | Real estate | 2022 |
| Hort Damn Limited | Administrative & support | 2025 |
| Horticman Limited | Agriculture & fishing | 2006 |
| Horus Consultants Limited | Professional & scientific | 2013 |
| Hospital Gateway Ltd | Information & communication | 2025 |
| Houghton Residential Lettings Limited | Real estate | 2014 |
| House of L.A Limited | Other services | 2025 |
| Housonmarketing Limited | Professional & scientific | 2016 |
| Howlett’S Professional Tree Services Ltd | Agriculture & fishing | 2024 |
| HP Finance & Leasing Limited | Financial services | 2018 |
| HR2GO Consultancy Ltd | Professional & scientific | 2021 |
| HSD Cables Ltd | Wholesale & retail | 2024 |
| HSM Housing Limited | Real estate | 2025 |
| Hudsons Stoves Ltd | Construction | 2013 |
| Huez Holdings Ltd | Financial services | 2018 |
| HUMPHREY11 Ltd | Professional & scientific | 2025 |
| Hunsdon Skip Hire Ltd | Water & waste | 2011 |
| Hunt & Forage Limited | Manufacturing | 2020 |
| Hunter & Hunter Maclean Ltd | Transport & logistics | 2019 |
| Hvac Design Solutions Ltd | Administrative & support | 2024 |
| Hyphosxai Ltd | Information & communication | 2026 |
| I Building Limited | Construction | 2017 |
| I Fence Ltd | Administrative & support | 2013 |
| I W 8 Construction Ltd | Construction | 2023 |
| I.H.H.Q. Limited | Real estate | 2001 |
| IAA Trade Services Ltd | Construction | 2026 |
| IAN Bowles Mountaineering Ltd | Construction | 2019 |
| IAN Clarke Russell Engineering Limited | Manufacturing | 2009 |
| ICB Alarm Systems Limited | Administrative & support | 2026 |
| Iconic Trading Cards Limited | Wholesale & retail | 2026 |
| Idiom Ltd | Administrative & support | 2019 |
| IL Food Limited | Wholesale & retail | 2014 |
| IMD Trading Ltd | Wholesale & retail | 2010 |
| Impact Compliance Solutions Limited | Public administration | 2016 |
| Impact Management & Consultancy Limited | Administrative & support | 2023 |
| IN Silico Translation Limited | Professional & scientific | 2011 |
| IN the MAD House Darts Ltd | Wholesale & retail | 2025 |
| Inclusion Project Management Limited | Professional & scientific | 2017 |
| Incorporated Sierra Leone Missionary Association(The) | Professional & scientific | 1906 |
| Infinibyte Ltd | Information & communication | 2012 |
| Inn Catering Limited | Hospitality | 2011 |
| Innovation & Technology Ltd | Professional & scientific | 2015 |
| Innovation Property Management Limited | Households | 2019 |
| Inside Talk Limited | Health & social care | 2023 |
| Insight DC Ltd | Professional & scientific | 2025 |
| Insight Integration London Limited | Construction | 2017 |
| Insightful Media Ltd | Information & communication | 2018 |
| Inspire Prestige Cars Limited | Wholesale & retail | 2014 |
| Inst.Edp Limited | Other services | 2021 |
| Instant Access Technologies Limited | Information & communication | 2002 |
| Intega Ltd | Professional & scientific | 2008 |
| Integrity Interiors Ltd | Construction | 2023 |
| Intelligent Electrical Services Ltd | Construction | 2010 |
| Interiofix Ltd | Construction | 2025 |
| Intimate Worship Experience Ltd | Other services | 2024 |
| IO Automation Limited | Manufacturing | 2019 |
| IQ Van's Transport & Logistics Ltd | Transport & logistics | 2025 |
| Ironex Limited | Construction | 2026 |
| Isiks Kitchen Ltd | Hospitality | 2019 |
| Isittoolate Ltd | Information & communication | 2010 |