| Icost-Ms Limited | Administrative & support | 2011 |
| ICP Building Solutions Group Limited | Financial services | 2015 |
| Icris Construction Ltd | Construction | 2025 |
| ICS SY Holdings Limited | Financial services | 2021 |
| ICX4 Ltd | Information & communication | 2013 |
| ID Checked Ltd | Information & communication | 2025 |
| Idahoaltrincham Limited | Wholesale & retail | 2025 |
| Idea Real Estate Limited | Real estate | 2025 |
| Idealworld Limited | Professional & scientific | 2024 |
| Identity Withheld Ltd | Professional & scientific | 2013 |
| IES Consulting Services Ltd | Professional & scientific | 2024 |
| IF Agency Group Ltd | Financial services | 2025 |
| Ifagency Limited | Professional & scientific | 2004 |
| Ifit Health & Fitness (Holdings) Limited | Other services | 1994 |
| Ifit Health & Fitness Limited | Other services | 1994 |
| IG IT Services Ltd | Information & communication | 2021 |
| IG Medical Services Ltd | Health & social care | 2021 |
| IGE Dollar Treasury Services | Financial services | 1919 |
| IGE USA Holdings | Financial services | 2015 |
| IGE USA Investments Limited | Professional & scientific | 1996 |
| Igent AI Limited | Information & communication | 2023 |
| Iglb Properties Limited | Real estate | 2019 |
| Ignatious Computer Services Limited | Information & communication | 2019 |
| Igroup 8 Limited | Administrative & support | 1999 |
| Ihadonelikethat Limited | Wholesale & retail | 2021 |
| Ihtek Limited | Professional & scientific | 2026 |
| IHU Creative Limited | Professional & scientific | 2025 |
| Iinneryou Ltd | Wholesale & retail | 2024 |
| Ije-Hospitality Ltd | Hospitality | 2020 |
| IJP Market Intelligence Limited | Financial services | 2024 |
| IKB Shine Limited | Real estate | 2023 |
| Ikon Consultancy Limited | Extraterritorial | 2004 |
| Ikonects Ltd | Real estate | 2023 |
| Iktec Limited | Professional & scientific | 2015 |
| Ikyzu Ltd | Hospitality | 2025 |
| Ilaria Coser Limited | Professional & scientific | 2022 |
| ILB Engineering(Uk) Limited | Professional & scientific | 2023 |
| Ilead Training Ltd | Education | 2026 |
| Iles Legal Limited | Professional & scientific | 2020 |
| Illamasqua (Holdings) Limited | Professional & scientific | 2007 |
| Illamasqua Limited | Wholesale & retail | 2007 |
| Illumina Business Limited | Administrative & support | 2022 |
| Illumion Ltd | Professional & scientific | 2022 |
| Ilmani Engineering Limited | Professional & scientific | 2015 |
| IM Dent Ltd | Health & social care | 2025 |
| Imaan MCR Ltd | Real estate | 2021 |
| Image Property Investments (UK) Limited | Real estate | 2011 |
| Imagine C.G.A. Ltd. | Administrative & support | 1993 |
| Imanash Ltd | Health & social care | 2021 |
| Imda Ltd | Real estate | 2021 |
| IMG UK Holdings Limited | Administrative & support | 2026 |
| Immo Cmac UK Ltd | Real estate | 2018 |
| Imoon Lighting (GB) Limited | Wholesale & retail | 2022 |
| Impact Project Management Services Limited | Professional & scientific | 2022 |
| Imperial Renovation Manchester Ltd. | Administrative & support | 2021 |
| Implandent Ltd | Health & social care | 2011 |
| Implement LS Limited | Administrative & support | 2014 |
| Imprint Publishing Ltd | Extraterritorial | 2019 |
| Improveasy (Eco) Ltd | Professional & scientific | 2022 |
| Improveasy (GCS) Ltd | Professional & scientific | 2022 |
| Improveasy (Installs) Ltd | Construction | 2017 |
| Improveasy (Services) Ltd | Professional & scientific | 2022 |
| Improveasy Ltd | Administrative & support | 2011 |
| Impuls Limited | Information & communication | 2022 |
| IN Group Holdings Limited | Extraterritorial | 2022 |
| IN Transit Carriers LLP | | 2018 |
| IN2CORPORATE Limited | Wholesale & retail | 2012 |
| Inact Limited | Administrative & support | 2014 |
| Inamilla Limited | Professional & scientific | 2023 |
| Inar Group Ltd | Professional & scientific | 2018 |
| Inar Properties Limited | Real estate | 2020 |
| Inarisec Limited | Professional & scientific | 2024 |
| Incentives for Administrative Consultants and Training Limited | Professional & scientific | 2019 |
| Incisive Smiles Holdings Limited | Financial services | 2018 |
| Incisive Smiles Woking Limited | Health & social care | 2019 |
| Include (Cheshire) Ltd | Health & social care | 2009 |
| Inclusiveedge Consulting Limited | Professional & scientific | 2023 |
| Inclusiville Empower C.I.C. | Hospitality | 2023 |
| Incol Partnership Ltd | Professional & scientific | 2019 |
| Income Plus Services (UK) Limited | Administrative & support | 2013 |
| Incredibble Limited | Professional & scientific | 2018 |
| Independent Catering Consultant Ltd | Hospitality | 2020 |
| Independent Psychiatry Consultancy (IPC) Limited | Health & social care | 2018 |
| Independent Roofing Inspection Specialists Ltd | Construction | 2013 |
| Independent Veterinary Behaviour Services Ltd | Professional & scientific | 2026 |
| Indian Lotus PVT Ltd | Professional & scientific | 2009 |
| Indigo Environmental Holdings Limited | Financial services | 2018 |
| Indigo Environmental Limited | Manufacturing | 2017 |
| Indigo EX Ltd | Wholesale & retail | 2025 |
| Indigo Lyon Limited | Wholesale & retail | 2009 |
| Indigo Octagon Ltd | Information & communication | 2011 |
| Indigo Orthodontic Solutions Ltd | Health & social care | 2019 |
| Indigo Polymers Limited | Administrative & support | 2018 |
| Indusganga Ltd | Wholesale & retail | 2023 |
| Industrial Facilities Management Limited | Professional & scientific | 2017 |
| Industrial Panel Systems Limited | Manufacturing | 2007 |
| Industrial Pipework & Mechanicals Limited | Construction | 2019 |
| Indy & FAI Collections Limited | Wholesale & retail | 2024 |
| Ineffable Intelligence Ltd | Professional & scientific | 2025 |
| Inevso Limited | Information & communication | 2017 |