| Intro Beauty Limited | Wholesale & retail | 2025 |
| Intuitech Solutions Ltd | Information & communication | 2020 |
| Invesdom Limited | Information & communication | 2013 |
| Investomate Ltd | Real estate | 2020 |
| Investro Properties Ltd | Real estate | 2023 |
| Invinceable Corals Ltd | Manufacturing | 2014 |
| Iomech Ltd | Professional & scientific | 2019 |
| Ionica Wine Ltd | Wholesale & retail | 2019 |
| IP Intelligence Limited | Administrative & support | 2020 |
| Ipac Technologies Limited | Information & communication | 2007 |
| IPG Services Ltd | Administrative & support | 2019 |
| IPM Civils Ltd | Construction | 2024 |
| IPR Electrical Ltd | Construction | 2021 |
| Iris One United Ltd | Education | 2024 |
| Iris Property Limited | Real estate | 2020 |
| Iron Rose Tattoo Limited | Other services | 2015 |
| Ironaxe IAO Ltd | Manufacturing | 2025 |
| Ironmoor Ltd | Wholesale & retail | 2013 |
| Isambard Consulting Limited | Extraterritorial | 2011 |
| Isaytheword Limited | Information & communication | 2022 |
| ISC Associates Ltd | Extraterritorial | 2025 |
| Iscientia Limited | Information & communication | 2007 |
| Isfi Express Limited | Wholesale & retail | 2021 |
| Isfi Properties Limited | Real estate | 2022 |
| Isha Rentals Ltd | Real estate | 2023 |
| Ishanan Limited | Information & communication | 2015 |
| Ishm Ltd | Health & social care | 2024 |
| Islamic Infrastructure Finance Forum Ltd | Other services | 2020 |
| ISM Logistics Ltd | Transport & logistics | 2025 |
| Isomade UK Limited | Wholesale & retail | 2020 |
| Isteni Flips Limited | Real estate | 2024 |
| Istoria Tours Ltd | Administrative & support | 2022 |
| IT Alliance Limited | Wholesale & retail | 2006 |
| IT Heroes Ltd | Information & communication | 2023 |
| IT Systems Solutions Limited | Information & communication | 2004 |
| Italian Journeys Limited | Administrative & support | 2003 |
| ITC Zone Ltd | Wholesale & retail | 2024 |
| ITM Services Limited | Professional & scientific | 2025 |
| ITP Cabling Ltd | Information & communication | 2012 |
| Itsumo Developing Ltd | Wholesale & retail | 2015 |
| It’S a Duck Ltd | Arts & recreation | 2025 |
| Iusta Cura Limited | Health & social care | 2024 |
| Ivan Musheto Ltd | Transport & logistics | 2011 |
| IVI Ventures Ltd | Professional & scientific | 2019 |
| Ivix Limited | Information & communication | 2014 |
| IVM Computing Ltd | Information & communication | 2025 |
| IVO Joinery Ltd | Construction | 2018 |
| Ivomes Consulting & Services Limited | Professional & scientific | 2009 |
| Ivpt Services Ltd | Construction | 2023 |
| IVS Decorating Ltd | Construction | 2016 |
| IVY Gate Property Group Limited | Real estate | 2013 |
| Iwaw Club Ltd | Education | 2020 |
| IX Electronic Exchange Limited | Information & communication | 2013 |
| IX III ER Ltd | Real estate | 2025 |
| IX Iiia ER Ltd | Real estate | 2025 |
| Izigo Ltd | Administrative & support | 2017 |
| IZZ Tech Ltd | Construction | 2024 |
| Izzi Properties Limited | Real estate | 2022 |
| Izzuddin Consultancy Ltd | Professional & scientific | 2002 |
| J & C Construction (Surrey) Ltd | Construction | 2012 |
| J & I Holdings Limited | Real estate | 2003 |
| J & N Legacy Ltd | Real estate | 2025 |
| J and J Eames Limited | Real estate | 2016 |
| J C Elite Limited | Real estate | 2020 |
| J C S Plumbing & Heating Limited | Construction | 2015 |
| J Childs Mortgages Limited | Professional & scientific | 2025 |
| J D Estimating Ltd | Professional & scientific | 2025 |
| J Devine Civil Engineering Ltd | Construction | 1974 |
| J G Waste Clearance Ltd | Water & waste | 2025 |
| J Mark Fisher Carshalton Limited | Wholesale & retail | 2026 |
| J Mcgrath & Sons Construction Limited | Construction | 2005 |
| J Property Rentals Ltd | Real estate | 2023 |
| J R Morris Construction Ltd | Construction | 2025 |
| J S Clarke Electrical Limited | Construction | 2003 |
| J Wardley Ltd | Manufacturing | 1973 |
| J White Technical Services Ltd | Construction | 2019 |
| J&D PVT Limited | Information & communication | 2015 |
| J&F Medicos Healthcare Ltd | Health & social care | 2015 |
| J&H Movies Ltd | Information & communication | 2020 |
| J&J Ceramics LAB Ltd | Health & social care | 2022 |
| J&M Capital Investment Group Limited | Real estate | 2026 |
| J&M Mechanical Services Group Limited | Construction | 2022 |
| J&M Studios Ltd | Professional & scientific | 2020 |
| J&S Rental Management Limited | Real estate | 2023 |
| J&Z DEN Practice Limited | Health & social care | 2025 |
| J-E-S London Limited | Construction | 2011 |
| J. a. H. Boyle Anaesthesia Limited | Health & social care | 2013 |
| J. Devine Plant Hire Limited | Administrative & support | 1982 |
| J. J. C. Wickham Limited | Construction | 2004 |
| J. Phillips Electrical Contractors Limited | Construction | 2003 |
| J.B. Communications Limited | Arts & recreation | 1970 |
| J.C.M. Retail Limited | Wholesale & retail | 2006 |
| J.G Property and Landscaping Services Ltd | Professional & scientific | 2026 |
| Jack Stalwart Limited | Information & communication | 2020 |
| Jackrabbit Comics Limited | Information & communication | 2023 |
| Jacob Oxford Ltd | Information & communication | 2026 |
| Jacs Care Consultancy Limited | Health & social care | 2016 |
| Jade Autos Ltd | Wholesale & retail | 1999 |
| Jaden Productions Limited | Arts & recreation | 2019 |
| Jaffna Spice Ltd | Hospitality | 2024 |