| Hopkinson Piano UK Co., Ltd | Professional & scientific | 2014 |
| Horace Assets Limited | Real estate | 2008 |
| Horace George Holdings Ltd | Hospitality | 2025 |
| Horizons Child Psychology Services Ltd | Health & social care | 2008 |
| Horse Feeding Solutions Ltd | Manufacturing | 2025 |
| Horseboxseller Ltd | Wholesale & retail | 2015 |
| Horsemanship Showcase Ltd | Information & communication | 2023 |
| Horsenality Ltd | Information & communication | 2022 |
| House of Solutions Limited | Information & communication | 2005 |
| Housty Homelift Co., Limited | Manufacturing | 2021 |
| Houz Mortgages Ltd | Financial services | 2022 |
| Howard Biopharma Consulting Limited | Professional & scientific | 2021 |
| HPS (Group) Limited | Professional & scientific | 2014 |
| HR Unboxed Ltd | Information & communication | 2025 |
| Hsauditco Limited | Professional & scientific | 2025 |
| Hshin World Enterprise Ltd | Professional & scientific | 2014 |
| Huafeng Exact Hardware Limited | Professional & scientific | 2009 |
| Huatone.It Co., Ltd | Professional & scientific | 2025 |
| Hubei Machinery & Equipment Overseas Industry Ltd | Professional & scientific | 2007 |
| Huffler.Com Ltd | Extraterritorial | 2012 |
| Hugeland Chemical Co., Limited | Professional & scientific | 2008 |
| Human Core Ltd | Professional & scientific | 2013 |
| Humbert & Ellis Ltd | Wholesale & retail | 2003 |
| Hunter Hounds Ltd | Wholesale & retail | 2020 |
| Hunters Coaches of Daventry Limited | Transport & logistics | 2007 |
| Hydrogen MX Ltd | Manufacturing | 2020 |
| Hylical Industrial Limited | Professional & scientific | 2007 |
| Hynton Consultants Limited | Professional & scientific | 2015 |
| IAN Cook Limited | Real estate | 1973 |
| IAN Halton Training Limited | Other services | 2005 |
| Iansb Ltd | Real estate | 2026 |
| ICA Express Ltd | Hospitality | 2024 |
| ICC Consultants Ltd | Professional & scientific | 2021 |
| Iconic Cinema Holdings Limited | Wholesale & retail | 2026 |
| Icosa Academy Ltd | Professional & scientific | 2026 |
| Icosa Ltd | Professional & scientific | 2024 |
| ID Bathrooms & Kitchens Ltd | Construction | 2023 |
| Ideal Independent Installations Ltd | Manufacturing | 2012 |
| Igryk Ltd | Construction | 2025 |
| II - VI U.K. Limited | Wholesale & retail | 1996 |
| Ikonic Transport Limited | Transport & logistics | 2018 |
| Iley Tech Limited | Information & communication | 2015 |
| Imimone Co., Ltd | Professional & scientific | 2026 |
| Immaculate Grace Care Ltd | Health & social care | 2014 |
| Immia Limited | Education | 2026 |
| Impower Events Ltd | Administrative & support | 2025 |
| In-Site Electrical Distributors Limited | Wholesale & retail | 1996 |
| IN1968 Ltd | Information & communication | 2021 |
| Indian Curry Chef Ltd | Hospitality | 2025 |
| Indigo Media & Events Ltd | Professional & scientific | 2010 |
| Indigo Mindful Solutions Ltd | Health & social care | 2023 |
| INDIGO23 Limited | Arts & recreation | 2011 |
| Indulgence Skin Laser & Beauty Clinic Ltd | Health & social care | 2016 |
| Industry & Supply Mercantile Store Ltd | Wholesale & retail | 2025 |
| Infinity Aerobatics Ltd | Extraterritorial | 2024 |
| Informed Accounting Solutions Limited | Professional & scientific | 2020 |
| Inmile Tech Limited | Wholesale & retail | 2021 |
| Inn Transport Ltd | Transport & logistics | 2022 |
| Inner Beam Counselling Limited | Health & social care | 2025 |
| Innova Building Ltd | Construction | 2024 |
| Innovations Plus Limited | Professional & scientific | 2011 |
| Insite Commercial Properties Ltd | Real estate | 2015 |
| Insite Electrical Wholesalers Limited | Wholesale & retail | 2019 |
| Inspiron Systems Ltd | Manufacturing | 2011 |
| Insulglass Limited | Manufacturing | 2008 |
| Integra Publishing Ltd | Information & communication | 2022 |
| Integrity CBT Ltd | Health & social care | 2014 |
| International Drinks Specialists LLP | | 2020 |
| International Management System Certification Group (UK) Limited | Professional & scientific | 2014 |
| Inveniet Limited | Professional & scientific | 2016 |
| Invleon Electric Co., Ltd | Professional & scientific | 2020 |
| ION Martin Ltd | Transport & logistics | 2020 |
| Ipabc Limited | Extraterritorial | 2013 |
| Irina Automation Technology Co., Limited | Wholesale & retail | 2020 |
| Irontree Ltd | Professional & scientific | 2024 |
| Irorun Foodhub Limited | Wholesale & retail | 2025 |
| Iscom Limited | Water & waste | 2010 |
| Island Commercial Vehicles Limited | Wholesale & retail | 1998 |
| Isotest Limited | Professional & scientific | 2020 |
| Ispeedcourier Ltd | Transport & logistics | 2025 |
| Ivps Technology UK Co., Ltd | Professional & scientific | 2016 |
| IVY Rose Developments Ltd | Real estate | 2024 |
| IVY Rose Investments Ltd | Financial services | 2019 |
| J & H Coffee Limited | Hospitality | 2017 |
| J Brougham Limited | Construction | 2019 |
| J Davis Holdings Limited | Professional & scientific | 2016 |
| J Dixon Builders (UK) Ltd | Other services | 2017 |
| J Howard Rigging Ltd. | Information & communication | 2021 |
| J M G Specialised Engineering Limited | Manufacturing | 1999 |
| J Nails Daventry Ltd | Other services | 2023 |
| J P Leeding Limited | Construction | 2012 |
| J P M Carpentry Ltd | Construction | 2016 |
| J&B Warren Ltd | Transport & logistics | 2025 |
| J&J Cladding Ltd | Construction | 2026 |
| J&J Removals and Storage Ltd | Transport & logistics | 2024 |
| J&P ENG Ltd | Professional & scientific | 2014 |
| J-Control Germany Industrial Co., Ltd | Manufacturing | 2021 |
| J.Divitae Ltd | Wholesale & retail | 2026 |
| J.P. Nightingale Ltd | Real estate | 2023 |
| JA Electrics Limited | Construction | 2004 |