| Hadenside Management Company Limited | Households | 1991 |
| Hague Explained CIC | Education | 2023 |
| Hairdressers (Cheshunt) Ltd | Other services | 2021 |
| Hampton Resources Limited | Wholesale & retail | 2006 |
| Hank Zarihs Associates Limited | Financial services | 2016 |
| Harbour Roast Limited | Hospitality | 2025 |
| Hardy Brown Limited | Real estate | 2022 |
| Hardy HR Consulting Limited | Administrative & support | 2023 |
| Hashem Financial Services Limited | Professional & scientific | 2015 |
| HAU Solutions Limited | Information & communication | 2011 |
| Haven Alfresco Ltd | Wholesale & retail | 2024 |
| Havenwood Children's Services Ltd | Health & social care | 2025 |
| Haylock Electrical Services Limited | Construction | 2000 |
| Hazardust Ltd | Water & waste | 2026 |
| HB Travel and Couriers Ltd | Transport & logistics | 2026 |
| Health and Safety Assurance Services Ltd | Professional & scientific | 2001 |
| Healthy Minds Therapy Ltd | Health & social care | 2022 |
| Heartsync Support Limited | Health & social care | 2024 |
| Heartwood Exhibitors Limited | Administrative & support | 2024 |
| Helen Ahmet Legal Ltd | Administrative & support | 2016 |
| Helen Ahmet Property Limited | Real estate | 2022 |
| Helenco Consulting Ltd | Real estate | 2023 |
| HEN House Artists London Ltd | Professional & scientific | 2021 |
| Henry Hadaway Organisation Limited | Information & communication | 1971 |
| Henson Fusion Ltd | Professional & scientific | 2018 |
| Here After NOW Studio Limited | Information & communication | 2024 |
| Hermanos Investments Limited | Construction | 2025 |
| Hertford Eatery Ltd | Hospitality | 2024 |
| Hertfordshire ZOO Limited | Extraterritorial | 2021 |
| Herts 24/7 Plumbing and Heating Ltd | Construction | 2022 |
| Herts Electrical Wholesale Limited | Wholesale & retail | 2004 |
| Herts Prestige UK Limited | Wholesale & retail | 2009 |
| Herts Tuition Ltd | Education | 2019 |
| HEY Presto Magic Limited | Information & communication | 2025 |
| HHO Entertainment Ltd | Manufacturing | 2005 |
| HHO Limited | Manufacturing | 2007 |
| HI Bar Ltd | Hospitality | 2020 |
| Hickman Holdings Ltd | Financial services | 2026 |
| High Food Ltd | Hospitality | 2022 |
| Hilamar Ltd | Other services | 2018 |
| Hillchester Assets LLP | | 2020 |
| Hillsquare Consulting Limited | Real estate | 2017 |
| Hillsquare Property Limited | Real estate | 2020 |
| Hindaw Property Limited | Real estate | 2020 |
| HM Plumbers and Builders Ltd | Construction | 2019 |
| HM Unique Products Ltd | Professional & scientific | 2009 |
| HNF Trading Limited | Information & communication | 2023 |
| Hodges Estates Ltd | Real estate | 2025 |
| Homeaiir Ltd | Wholesale & retail | 2022 |
| Homwood Limited | Financial services | 2025 |
| Hotshot Agency Ltd | Information & communication | 2020 |
| House Manor Management Limited | Households | 2012 |
| House of Penelope P Ltd | Manufacturing | 2026 |
| Hphr Consult Ltd | Professional & scientific | 2020 |
| HTC Legal Services Limited | Professional & scientific | 2021 |
| Hub Repairs Limited | Manufacturing | 2026 |
| Hunter Financial Limited | Financial services | 2014 |
| Hunts Barn Limited | Real estate | 2019 |
| HUS Ragip Productions Limited | Information & communication | 2021 |
| Husky Home Lettings Limited | Real estate | 2025 |
| Huthman Limited | Information & communication | 2016 |
| Hyperaeon Ltd | Information & communication | 2026 |
| HZA Data Systems Limited | Information & communication | 2024 |
| I Bowen Limited | Construction | 2023 |
| I.P. Electrical Appliance Services Limited | Real estate | 1966 |
| IAN Douglas Design & Print Limited | Manufacturing | 2021 |
| IC Boilers Ltd | Construction | 2021 |
| Icam Chocolate UK Ltd | Hospitality | 2010 |
| Icarus Computer Systems Limited | Information & communication | 1979 |
| Iconic Concepts Limited | Education | 2013 |
| ID Plumbing Heating Limited | Construction | 2018 |
| Ideal Nest Limited | Real estate | 2020 |
| IG Meridian Property Group Ltd | Real estate | 2026 |
| Ijoba Financial Services Limited | Financial services | 2025 |
| Imageynation Ltd. | Administrative & support | 2007 |
| Immersive Sport Ltd | Arts & recreation | 2018 |
| Inca Property Limited | Real estate | 2020 |
| Inclusitech Ltd | Administrative & support | 2024 |
| Infiniti Trading Ltd | Wholesale & retail | 2020 |
| Inform Data Solutions Limited | Information & communication | 2023 |
| Information Solutions Architecture Ltd | Information & communication | 2012 |
| Information Technology Solutions Limited | Information & communication | 2015 |
| Inner Power Building Facility Service’S Ltd | Construction | 2025 |
| Innofinity Limited | Wholesale & retail | 2021 |
| Interior Development Solutions Ltd | Construction | 2010 |
| International Academy of Media and Diplomacy Ltd. | Administrative & support | 2020 |
| Investdc Ltd | Construction | 2020 |
| Ipro Systems Ltd | Information & communication | 2018 |
| Ipsum Solutions Limited | Information & communication | 2016 |
| Isrn 2025 Limited | Real estate | 2025 |
| Itt.Trading Ltd | Hospitality | 2019 |
| IVL Accountancy Limited | Professional & scientific | 2018 |
| J G-P Counselling Ltd | Health & social care | 2023 |
| J Pathan Clinical Services Ltd | Health & social care | 2023 |
| J T Bowtell & Associates Professional Services Limited | Public administration | 2024 |
| J.H.Nelson Meat Traders Limited | Wholesale & retail | 2020 |
| JAA Electrical Ltd | Construction | 2023 |
| Jacinta Makeup Ltd | Other services | 2024 |
| Jackpot Media Ltd | Information & communication | 2011 |
| Jacob Macey Ltd | Other services | 2019 |