| Humdania Ltd | Real estate | 2020 |
| Hunterx Limited | Wholesale & retail | 2025 |
| Huzi Ltd | Wholesale & retail | 2024 |
| HVY Limited | Administrative & support | 2011 |
| Hybreeze Refrigeration & Air Conditioning Ltd | Manufacturing | 2019 |
| Hydraulic Solutions Limited | Other services | 1995 |
| Hydronair Ltd | Wholesale & retail | 2022 |
| HYK Consultants UK Ltd | Professional & scientific | 2024 |
| I Ahmed Transport Ltd | Transport & logistics | 2026 |
| I AM Unstoppable Limited | Manufacturing | 2019 |
| I B London Constructions Ltd | Construction | 2023 |
| I Henry Building Maintenance Ltd | Construction | 2025 |
| I Mirza Limited | Health & social care | 2018 |
| I-Care Medical Ltd | Health & social care | 2015 |
| I.G. Welding Ltd | Construction | 2025 |
| I.T.N Gardening Services Limited | Administrative & support | 2015 |
| I2I Marketing Solutions Limited | Professional & scientific | 2000 |
| IAN Johnson Construction Services Limited | Professional & scientific | 2009 |
| IB Barber Coulsdon Ltd | Other services | 2024 |
| Ib&Z Ltd | Wholesale & retail | 2019 |
| Ibbtech Limited | Information & communication | 2018 |
| Ibus Limited | Transport & logistics | 2026 |
| Ice Cream Birmingham Ltd | Hospitality | 2026 |
| Iclick Technologies Ltd | Information & communication | 2024 |
| Iclublondon Limited | Professional & scientific | 2013 |
| Icon Tax Limited | Professional & scientific | 2011 |
| Icon TEX Limited | Wholesale & retail | 2025 |
| ID Bespoke Ltd | Construction | 2019 |
| Ideal Drilling Ltd | Financial services | 2022 |
| Ideal Land Solutions Limited | Construction | 2017 |
| Ideal London Ltd | Wholesale & retail | 2018 |
| Idenity Worldwide Limited | Information & communication | 2026 |
| Idiaz Property Solutions Ltd | Real estate | 2022 |
| Idiia Ltd | Households | 2017 |
| Idoma Tech Limited | Other services | 2024 |
| IDS Design&Build Ltd | Construction | 2016 |
| Ignatov Ltd | Other services | 2013 |
| Ignis Code Limited | Information & communication | 2023 |
| IGT Lift Ltd | Construction | 2017 |
| Ih&Mac Properties Ltd | Households | 2019 |
| Ihsaan Productivity Ltd | Wholesale & retail | 2024 |
| Ije-Eze Limited | Health & social care | 2018 |
| Ijet Ltd | Administrative & support | 2025 |
| IK Decorating Limited | Construction | 2025 |
| IK Merton Care & Education Center Limited | Other services | 2022 |
| IK Muslim Needs Limited | Other services | 2022 |
| Ikhaya Imba Properties Ltd | Real estate | 2026 |
| Ikor Ltd | Wholesale & retail | 2025 |
| ILE Iyan by Pods Ltd | Hospitality | 2025 |
| Illyrian Motors Ltd | Wholesale & retail | 2026 |
| IM Fitness Ltd | Arts & recreation | 2017 |
| Imanos Ltd | Wholesale & retail | 2025 |
| Imkrc Limited | Wholesale & retail | 2020 |
| Immersia Labs Limited | Information & communication | 2025 |
| Impact Beyond the Brand Limited | Professional & scientific | 2026 |
| Impeccable Shop Ltd | Wholesale & retail | 2023 |
| Impel Overseas Education Ltd | Information & communication | 2022 |
| Imperiabuild Limited | Construction | 2024 |
| Imperial Care Services Limited | Other services | 2016 |
| Imperial Collection Ltd | Wholesale & retail | 2026 |
| Imperial Telecomms Limited | Information & communication | 2014 |
| Imperium Financial Services Ltd | Professional & scientific | 2016 |
| Impress Care Ltd | Health & social care | 2016 |
| Impreza Enterprise Ltd | Other services | 2024 |
| Improve Confidence in Life Limited | Administrative & support | 2017 |
| Imran Shah Limited | Transport & logistics | 2025 |
| IN Veritas Medics Ltd | Wholesale & retail | 2021 |
| Incore IT Ltd. | Wholesale & retail | 2021 |
| Incrementum Associates Ltd | Real estate | 2022 |
| Indulge Trading Ltd | Wholesale & retail | 2024 |
| Industates Limited | Extraterritorial | 1973 |
| Industrial GAS Springs Group Holdings Limited | Financial services | 2018 |
| Industrial GAS Springs Limited | Manufacturing | 1983 |
| Industrial Projects Solutions Ltd | Construction | 2026 |
| Industrial Siteworks Solutions Ltd | Construction | 2012 |
| Infinite Construction and Building Ltd | Construction | 2024 |
| Infinite Snds Ltd | Arts & recreation | 2024 |
| Infinitebinary Limited | Information & communication | 2023 |
| Infinitesoul 73 Ltd | Construction | 2022 |
| Infinity Creative Arts Ltd | Arts & recreation | 2022 |
| Infinity Learning Ltd | Education | 2021 |
| Informdata Ltd | Other services | 2013 |
| INFORNOTHING80 Limited | Construction | 2020 |
| Infranexus Limited | Construction | 2026 |
| Ingenea Limited | Professional & scientific | 2005 |
| Ingeniusly Corporate Ltd | Professional & scientific | 2024 |
| Ingira | Arts & recreation | 2012 |
| Inkko Ltd | Construction | 2011 |
| Inli Ltd | Other services | 2015 |
| Innodia Ltd | Information & communication | 2011 |
| Innovate & Create Construction Ltd | Construction | 2025 |
| Inovate London Limited | Construction | 2011 |
| Inspire Youths CIC | Health & social care | 2020 |
| Inspired by Africa Ltd | Wholesale & retail | 2021 |
| Inspired Consultants Ltd | Information & communication | 2022 |
| Instructify Limited | Professional & scientific | 2024 |
| Insubuild Solutions Ltd | Construction | 2024 |
| Intalock Limited | Professional & scientific | 2012 |
| Integral Accounts Limited | Professional & scientific | 2024 |
| Integral Recruiters Global Ltd | Administrative & support | 2024 |