| Helbar Automation Limited | Manufacturing | 2003 |
| Helen Williams Consulting Limited | Information & communication | 2002 |
| Helm London Limited | Wholesale & retail | 2022 |
| Helvadjian Heritage Limited | Professional & scientific | 2025 |
| HEN and Ivln Ltd | Construction | 2020 |
| Henderson Property Management Solutions Ltd | Real estate | 2018 |
| Henstock Mortgage & Protection Consultant Limited | Professional & scientific | 2015 |
| Henstock Residential Limited | Real estate | 2020 |
| Heron CAY Ltd | Professional & scientific | 2024 |
| HGC Group Limited | Construction | 2020 |
| HGM Mechanical Limited | Construction | 2019 |
| HH Therapy Ltd | Health & social care | 2022 |
| HHE Consultancy Ltd | Professional & scientific | 2025 |
| High Grade Metal Polishers Limited | Manufacturing | 2006 |
| High Leas PV Ltd | Energy | 2015 |
| Hill-Allen & Co. (Gidea Park) Ltd | Professional & scientific | 1998 |
| Hillfield Estates Limited | Real estate | 1999 |
| Hills Residential Lettings Ltd | Real estate | 2024 |
| Hilton Engineering Limited | Information & communication | 2004 |
| Hinkco Ltd | Real estate | 2025 |
| Hippocrates Ltd | Financial services | 2023 |
| Hitech IT Consultancy Services Ltd | Information & communication | 2025 |
| Hodgson & Regan Maintenance Ltd | Construction | 2014 |
| Holben Management Ltd | Professional & scientific | 2023 |
| Holdgate Limited | Professional & scientific | 2023 |
| Holme Wood Lane Energy Centre Limited | Energy | 2025 |
| Holmes Automotive Installations Ltd | Wholesale & retail | 2021 |
| Holmes Roofing & Co Limited | Construction | 2023 |
| Holt Physio Ltd | Health & social care | 2015 |
| Home Away Pet Services Ltd | Other services | 2024 |
| Home Counties Motor Maintenance Limited | Wholesale & retail | 2024 |
| Home Lift Aftercare Ltd | Construction | 2019 |
| Home Secure Solutions Limited | Administrative & support | 2010 |
| Homelifts UK Limited | Construction | 2021 |
| Homemates Construction Ltd | Construction | 2025 |
| Homes Direct Development Company Limited | Construction | 2026 |
| Hopestock Ltd | Financial services | 2017 |
| Hopkins International Ltd | Information & communication | 2008 |
| Horchex Ltd | Professional & scientific | 2015 |
| Horror Tales Productions Limited | Information & communication | 2023 |
| House & Co Limited | Professional & scientific | 2011 |
| House of Barker Ltd | Professional & scientific | 2015 |
| House on the Hill Wine Limited | Hospitality | 2024 |
| HOW Construction Ltd | Construction | 2024 |
| Howard & Stapleton Limited | Administrative & support | 2002 |
| Howdenshire Holdings Ltd | Construction | 2020 |
| Howdenshire Homes Ltd | Construction | 2020 |
| Hresult Limited | Professional & scientific | 2019 |
| HRP Bricklaying & Landscaping Limited | Construction | 2025 |
| HRV Solutions Group Ltd | Financial services | 2026 |
| HSE Consulting (UK) Ltd | Professional & scientific | 2010 |
| HSE Group Limited | Public administration | 2024 |
| HSE Property Compliance Ltd | Professional & scientific | 2023 |
| Hse-Compliance Ltd | Professional & scientific | 2023 |
| HSH Property Consultants Limited | Professional & scientific | 2010 |
| Hunt ADR Limited | Professional & scientific | 2016 |
| Hurley Broadoak Ltd | Real estate | 2024 |
| Hutton (Sheldon Court) Management Company Limited | Real estate | 1979 |
| Hyde Wood Topsoil T/A ALL Waste Movements Limited | Water & waste | 1994 |
| HYDRO4PAWS Limited | Other services | 2013 |
| Hydrocarbon Support Services Ltd. | Professional & scientific | 2014 |
| Hypokart Limited | Wholesale & retail | 2025 |
| I & S Health Care Ltd | Health & social care | 2015 |
| ICM Electrical LLP | | 2016 |
| Icshana Ltd | Information & communication | 2024 |
| ICU Plumbing Limited | Construction | 2018 |
| IF Technical Services Ltd | Professional & scientific | 2022 |
| Ileostomy and Internal Pouch Association | Professional & scientific | 2016 |
| Ilford Homes Limited | Health & social care | 2008 |
| Images (Danbury) Limited | Other services | 2019 |
| IMS Consultancy Services (UK) Limited | Information & communication | 2012 |
| Indelsworld Ltd | Manufacturing | 2023 |
| Independent Asbestos Solutions Limited | Construction | 2014 |
| Infinity Medical Limited | Other services | 2005 |
| Ingatestone Gatehouse Residents Association Limited | Households | 1984 |
| Inifer Potter & SON Holdings Limited | Professional & scientific | 2000 |
| Inifer Potter & SON Limited | Wholesale & retail | 2000 |
| Inkgenx Ltd | Information & communication | 2023 |
| Inkspot Limited | Professional & scientific | 2010 |
| INNOV18 Ltd | Wholesale & retail | 2008 |
| Inovivo Ltd | Information & communication | 2019 |
| Intelcomm (UK) Limited | Manufacturing | 1989 |
| Intelligent Planning Limited | Administrative & support | 2015 |
| Investmentleads Ltd | Administrative & support | 2018 |
| Ionic Digital Ltd | Information & communication | 2019 |
| IP Shepard Ltd | Professional & scientific | 2023 |
| Ipeco Holdings Limited | Manufacturing | 1960 |
| IR Telecoms & Management Limited | Information & communication | 2021 |
| Irof Eco Limited | Construction | 2024 |
| Irontrading Limited | Financial services | 2016 |
| Ironwood Capital Developments Ltd | Construction | 2022 |
| Isthmus Consulting Ltd | Professional & scientific | 2017 |
| IT Insight Limited | Information & communication | 1986 |
| Iterz Ltd | Information & communication | 2011 |
| IVY Property Services (Essex) Limited | Construction | 2024 |
| IX Cameras Ltd | Manufacturing | 2014 |
| J & J Restaurants Limited | Professional & scientific | 2003 |
| J & M Investment Holdings | Financial services | 2026 |
| J & P Prior Cleaning Services Ltd | Administrative & support | 2013 |
| J Deklerk Consulting Limited | Professional & scientific | 2023 |