| Ideal Hvac Limited | Financial services | 2018 |
| Idream Galaxy Ltd | Administrative & support | 2023 |
| Iedit Limited | Information & communication | 2011 |
| IGI Fitting Crew Limited | Other services | 2019 |
| Ihealthnano Ltd | Other services | 2021 |
| IJ Facilities Management Limited | Administrative & support | 2014 |
| IKK UK 2 Ltd | Real estate | 2023 |
| IL Acquisitions Limited | Information & communication | 2020 |
| IL Holdco Limited | Financial services | 2020 |
| Ilaiv ALB Limited | Wholesale & retail | 2026 |
| Ilearnexperts Ltd | Information & communication | 2009 |
| Ileasecars Limited | Administrative & support | 2013 |
| ILM Global Education Group Ltd | Information & communication | 2026 |
| Ilupeju Transport Ltd | Transport & logistics | 2022 |
| IM Luxury Garden & Build Ltd | Construction | 2026 |
| Imag Electronics Holdings Limited | Wholesale & retail | 2013 |
| Imagine Computing Limited | Real estate | 2001 |
| Imagine Freehold Limited | Financial services | 2021 |
| Imola Properties Limited | Real estate | 2018 |
| Impact Sports Management Limited | Arts & recreation | 2004 |
| Imperial Coins (Group) Limited | Extraterritorial | 2004 |
| Imperial Coins (Investments) Limited | Administrative & support | 2004 |
| Imperial Coins (London) Limited | Administrative & support | 2007 |
| Imperial Coins Limited | Wholesale & retail | 2003 |
| Imperium Group Ulev Ltd | Construction | 2020 |
| Imperium Holdings London Ltd | Real estate | 2018 |
| Imperium Holdings SB Ltd | Real estate | 2025 |
| Impero Security Limited | Administrative & support | 2023 |
| IN Grime WE Trust Ltd | Wholesale & retail | 2017 |
| Inchcape Residents Association Limited | Construction | 1970 |
| Incka Ltd | Professional & scientific | 2020 |
| Incorporated Limited | Other services | 2023 |
| Independent Care (Essex) Limited | Real estate | 2015 |
| Independent Doctors Federation | Other services | 1992 |
| Independent Scrap Co. Limited | Water & waste | 2003 |
| Indescon Court Trustee 1 Limited | Administrative & support | 2020 |
| Indescon Court Trustee 2 Limited | Administrative & support | 2020 |
| Indifood Ltd | Hospitality | 2026 |
| Indigo Clothing Ltd | Wholesale & retail | 2002 |
| Indigo UK Strategic Land Investments LP | | 2011 |
| Indo-Global Cultural Forum | Arts & recreation | 2023 |
| Industrial Facades Logistics Ltd | Construction | 2019 |
| Industry Expo Limited | Administrative & support | 2019 |
| Infinistats Ltd | Information & communication | 2012 |
| Infinitas Security Limited | Administrative & support | 2010 |
| Infinite 360 Works Ltd | Construction | 2025 |
| Infinity Cabling Limited | Information & communication | 2013 |
| Infocomms Consultancy Limited | Information & communication | 2012 |
| Ingheads Properties Limited | Real estate | 2016 |
| Ingleton Electrical Services Ltd | Construction | 2025 |
| Inhaus Elemental Solutions Ltd | Professional & scientific | 2019 |
| Initium Consulting Ltd | Professional & scientific | 2016 |
| Inkshed Creative Ltd | Administrative & support | 2014 |
| Inlife Management Ltd | Professional & scientific | 2018 |
| Innovate Design and Build Ltd | Construction | 2019 |
| Innovation Roofing & Building Solutions Ltd | Construction | 2026 |
| Innovative Icons Limited | Wholesale & retail | 2014 |
| Inoa Dryline Ltd | Construction | 2023 |
| INOV8 Tech Ltd | Information & communication | 2026 |
| Insecta Pest Solutions Ltd | Administrative & support | 2023 |
| Insert Independent Ltd | Information & communication | 2013 |
| Inside JOB by Lellow Limited | Other services | 2016 |
| Insideinfo Music Ltd | Information & communication | 2011 |
| Insideout Advisors Limited | Professional & scientific | 2016 |
| Instal Team Limited | Construction | 2014 |
| Instar Capital Limited | Financial services | 2026 |
| Integra Back Office Solutions Limited | Professional & scientific | 2012 |
| Integra Software Solutions Limited | Information & communication | 2016 |
| Integrating the Enterprise Limited | Professional & scientific | 2008 |
| Integrative Acupuncture Ltd | Health & social care | 2020 |
| Intellicycle UK Limited | Wholesale & retail | 2025 |
| Interim Recruitment Services Limited | Administrative & support | 2021 |
| Interiors Simple Fitted Limited | Construction | 2022 |
| Internal Solutions and Services Limited | Construction | 2009 |
| International Huckleberry Chicken Limited | Hospitality | 2020 |
| International Pleasure Motors PVT Ltd | Wholesale & retail | 2024 |
| Internet Communications Limited | Information & communication | 1994 |
| Interstellar Holdings Limited | Financial services | 2023 |
| Intersys Holdings Limited | Financial services | 2023 |
| Intersys Limited | Information & communication | 1996 |
| Intersys Software Limited | Wholesale & retail | 2024 |
| Into Infinity Limited | Wholesale & retail | 2020 |
| Intuitive Techniques Limited | Administrative & support | 2010 |
| Investor in Customers Ltd | Administrative & support | 2006 |
| Invicta Commerce Limited | Wholesale & retail | 2022 |
| Inwood Partners Limited | Manufacturing | 2022 |
| IPP Building Maintenance Limited | Construction | 2008 |
| IPS Vision Ltd | Information & communication | 2007 |
| Ipsonne Holdings Limited | Financial services | 2017 |
| IRC Entertainment Limited | Information & communication | 2025 |
| Irie Ventures Ltd | Professional & scientific | 2024 |
| Iron Forge Fitness Ltd | Education | 2025 |
| ISA Express Ltd | Transport & logistics | 2020 |
| Isaac Services Limited | Water & waste | 2026 |
| ISD Properties Limited | Construction | 1965 |
| Island Blue London Limited | Manufacturing | 2015 |
| Islandbridge Algers Limited | Construction | 2017 |
| Islandbridge Chigwell Limited | Administrative & support | 2016 |
| Islandbridge Loughton Limited | Construction | 2016 |
| Islandbridge Properties Limited | Real estate | 2009 |