| Hurn Electrical Ltd | Construction | 2019 |
| Huseyin Askin Ltd | Extraterritorial | 2026 |
| Hutch X Haines - ICU Ltd | Administrative & support | 2024 |
| Hutson Investment Holdings Limited | Real estate | 2025 |
| Hutton Court (London) RTM Company Limited | Real estate | 2025 |
| HUY Hoang II Sewing Co., Ltd | Extraterritorial | 2016 |
| Huzur Retirement Strategies Ltd | Financial services | 2023 |
| HWG Properties Limited | Real estate | 2016 |
| Hy-Grade Domestic Building Services Limited | Construction | 2008 |
| Hyacinth Holdings Limited | Households | 2024 |
| Hybric Limited | Real estate | 2018 |
| Hycom Trading Ltd | Financial services | 2021 |
| Hylas Yachts Limited | Wholesale & retail | 1997 |
| HYM Global Ltd | Information & communication | 2024 |
| Hymnal Global Limited | Administrative & support | 2025 |
| Hyphen Construction LLP | | 2021 |
| Hypnocoaching With OZY Ltd | Other services | 2023 |
| Hyrstdene Residents' Society Limited | Households | 1964 |
| I 2 Chauffeurs Limited | Transport & logistics | 2016 |
| I AM Bert Limited | Administrative & support | 2017 |
| I AM Construction Recruitment Ltd | Administrative & support | 2024 |
| I AM Real Estate Limited | Real estate | 2021 |
| I B Investments Limited | Financial services | 2007 |
| I Love Pensions Ltd | Professional & scientific | 2026 |
| I Monitor FS Ltd | Administrative & support | 2019 |
| I Murrell Plumbing & Heating Ltd. | Construction | 2005 |
| I-Learner Driving School Limited | Education | 2026 |
| I-Shine Cleaners Ltd | Administrative & support | 2019 |
| I. Higginson and Sons Roofing and Building Contractors Limited | Construction | 2003 |
| I. Schein Ltd | Administrative & support | 2014 |
| I.J.K. Enterprises Limited | Arts & recreation | 1977 |
| I.S French Polishing Limited | Construction | 2014 |
| I.T.P.(London)Limited | Financial services | 1944 |
| I2G Consulting Ltd | Professional & scientific | 2021 |
| I3PT Certification (UK) Limited | Construction | 2019 |
| IA Harris & SON Limited | Manufacturing | 2002 |
| IAG Estates Ltd | Construction | 2025 |
| IAM Surgery Limited | Health & social care | 2017 |
| Iamsamdrums Ltd | Arts & recreation | 2022 |
| IAN Cutts Associates Limited | Construction | 1996 |
| IAN Timothy Roberts Limited | Professional & scientific | 2016 |
| IB Legacy Group Ltd | Manufacturing | 2024 |
| IBE Humanoids Ltd | Construction | 2025 |
| IBE Partnership LLP | | 2010 |
| Ibkhas Services Limited | Construction | 2016 |
| Ibo-Express Limited | Wholesale & retail | 2024 |
| Iboaga Limited | Hospitality | 2020 |
| IBS Holdings Limited | Professional & scientific | 2006 |
| Ibzzy Ltd | Transport & logistics | 2025 |
| IC Contractor Services Limited | Administrative & support | 2022 |
| IC Interior Concept Ltd | Construction | 2013 |
| ICD Solutions Ltd | Hospitality | 2013 |
| Ickleh IT Systems Ltd | Information & communication | 2017 |
| Icon Collections International Limited | Financial services | 1999 |
| Iconic Black Taxis London Group Ltd | Administrative & support | 2005 |
| Iconic Business UK Limited | Wholesale & retail | 2024 |
| Iconic Intel Ltd | Information & communication | 2026 |
| Icool Environmental Ltd | Energy | 2020 |
| ICS (Hygiene) Limited | Administrative & support | 2006 |
| ICU Security Systems Ltd | Administrative & support | 2013 |
| ID7 Digital Limited | Information & communication | 2013 |
| Ideal World International UK Ltd | Wholesale & retail | 2022 |
| IDM Exporting Co Ltd | Extraterritorial | 2012 |
| Idyllic Homes Ltd | Real estate | 2020 |
| Ielevate Ltd | Construction | 2024 |
| IEO Services Limited | Administrative & support | 2023 |
| IF Holdings Limited | Financial services | 2020 |
| IG Coaching Ltd | Health & social care | 2022 |
| IG Promotions Limited | Extraterritorial | 2018 |
| IGF 2013 Ltd | Professional & scientific | 2013 |
| IGF8 Ltd | Real estate | 2011 |
| Iggy and Burt Limited | Wholesale & retail | 2017 |
| Ignition Property Investments Limited | Real estate | 2025 |
| Ignixip Limited | Information & communication | 2026 |
| Ihomeuk Ltd | Financial services | 2022 |
| IJK Recordings Limited | Information & communication | 2001 |
| Ikeja Logistic Ltd | Transport & logistics | 2020 |
| Ikonity Ltd | Information & communication | 2025 |
| Ileri Holdings Ltd | Other services | 2023 |
| ILEX-9 Ltd | Information & communication | 2018 |
| Illyria Consulting Limited | Information & communication | 2014 |
| Ilobloom Ltd | Other services | 2024 |
| IM Software Ltd | Information & communication | 2002 |
| Imade Media Limited | Information & communication | 2013 |
| Imageworx Limited | Other services | 2006 |
| IMF Stoves Limited | Construction | 2024 |
| Imir Properties Ltd | Financial services | 2021 |
| IMK Services Ltd | Real estate | 2023 |
| IMN Security Limited | Administrative & support | 2008 |
| Imobile and Phones Ltd | Wholesale & retail | 2026 |
| Impact and Willow Brook Management Company Limited | Households | 2013 |
| Impact Knowledge Education Technology Limited | Education | 2021 |
| Imperial Builders Ltd | Extraterritorial | 2023 |
| Imperial Court (Beckenham) Residents Association Limited | Real estate | 1998 |
| Imperial Court (Management Company) Limited | Real estate | 2008 |
| Imperial Court (Mitcham) RTM Company Limited | Real estate | 2021 |
| Imperial Harmony Limited | Hospitality | 2024 |
| Imperial Manor Limited | Health & social care | 2024 |
| Imperial Service Station Limited | Wholesale & retail | 2000 |
| Imperio Luxury Transport Ltd | Transport & logistics | 2026 |