| Issb Limited | Administrative & support | 1979 |
| Issy Consulting Ltd | Professional & scientific | 2012 |
| Issy Hope Projects | Other services | 2025 |
| Issy Investments Ltd | Financial services | 2018 |
| Issy Properties Ltd | Real estate | 2022 |
| Issy View Nanny Care Ltd. | Health & social care | 2023 |
| IT Concepts Ltd | Information & communication | 2013 |
| IT ERP Solutions Ltd | Information & communication | 2025 |
| IT IS Done Limited | Information & communication | 2018 |
| IT Planners Limited | Professional & scientific | 2025 |
| It's Bazaar Limited | Wholesale & retail | 2023 |
| ITA Aktagro Ltd | Administrative & support | 2023 |
| Italia Special Food Ltd | Wholesale & retail | 2018 |
| Italian Breaks Limited | Administrative & support | 2008 |
| Italian Exclusive Food Ltd | Hospitality | 2016 |
| Italian Living Style Ltd | Wholesale & retail | 2024 |
| Italian Merchant Ltd | Wholesale & retail | 2024 |
| Italian Touch Ragu Limited | Hospitality | 2023 |
| Italko Vegan Limited | Hospitality | 2016 |
| Italora World Ltd | Real estate | 2023 |
| Italy & Italy Limited | Administrative & support | 2020 |
| Italy Dema Green Fertilizer Co., Ltd | Administrative & support | 2024 |
| Itbp Limited | Information & communication | 2009 |
| Ite-Consulting Ltd | Information & communication | 2006 |
| Itea NGO Ltd | Information & communication | 2024 |
| Itea Solutions Limited | Information & communication | 2022 |
| Itech Warehouse Ltd | Wholesale & retail | 2018 |
| Itford Farm Ltd | Real estate | 2006 |
| Ithaca Aesthetic Surgery Limited | Health & social care | 2021 |
| Ithraa Ltd | Information & communication | 2025 |
| Itievk Limited | Information & communication | 2010 |
| Itihad Management Limited | Real estate | 2017 |
| ITS a Girls World Ltd | Other services | 2015 |
| ITS Hardy Homes Limited | Construction | 2023 |
| Itseven Ltd | Information & communication | 2017 |
| IUK Tech Ltd | Wholesale & retail | 2025 |
| Iulabs Ltd | Wholesale & retail | 2022 |
| Iunlock Tech Limited | Wholesale & retail | 2015 |
| Ivanovaice Ltd | Other services | 2025 |
| Ivanrey Entertainment Limited | Administrative & support | 2024 |
| Ives Plumbers Merchants Limited | Administrative & support | 2007 |
| Ivies Social Care Limited | Health & social care | 2014 |
| Iview International Limited | Administrative & support | 2019 |
| Ivory Estates Ltd | Real estate | 2025 |
| Ivory World Travels and Tours Limited | Administrative & support | 2013 |
| IVP Building Contractors Ltd | Construction | 2026 |
| IVY Chanel Limited | Administrative & support | 2016 |
| IVY Development Group Ltd | Administrative & support | 2015 |
| IVY London Ltd | Hospitality | 2019 |
| IVY Reign Ltd | Professional & scientific | 2024 |
| Ivy-Rose Hair Ltd | Other services | 2021 |
| Ivytree Nursery Twickenham Ltd | Education | 2024 |
| IYI Consultancy Ltd | Financial services | 2020 |
| Iyqon Ltd | Arts & recreation | 2020 |
| IZ Real Estate Limited | Professional & scientific | 2025 |
| Izza Limited | Other services | 2012 |
| J & a Autos Ltd | Professional & scientific | 2013 |
| J & a Commerce Ltd | Wholesale & retail | 2018 |
| J & B Impress Company Limited | Administrative & support | 1998 |
| J & D Inns Ltd | Hospitality | 2019 |
| J & Freitas Builders & Plumbers Ltd. | Administrative & support | 2019 |
| J & J Building Services (UK) Ltd | Construction | 2018 |
| J & J Confectionery Limited | Wholesale & retail | 1998 |
| J & K Apartments Limited | Hospitality | 2004 |
| J & N Homes Limited | Real estate | 2017 |
| J & S General Stores Limited | Wholesale & retail | 2001 |
| J & Z Data Solutions Ltd | Information & communication | 2022 |
| J a G Consultants Ltd | Other services | 2023 |
| J a Horney Ltd | Construction | 2015 |
| J ADU Security Limited | Information & communication | 2016 |
| J B Cradles & Scaffolding Ltd | Construction | 2018 |
| J C & T Properties Limited | Real estate | 2014 |
| J Cafe Limited | Hospitality | 2017 |
| J Coyne Properties Limited | Real estate | 2019 |
| J Dimond Conservation Limited | Other services | 2007 |
| J Griffith Properties Ltd | Hospitality | 2024 |
| J Group Consulting Ltd | Professional & scientific | 2014 |
| J H Baggri Limited | Real estate | 2019 |
| J J Electrical Installations Ltd | Construction | 2008 |
| J J Yavika Trade Software Ltd | Information & communication | 2025 |
| J L Skipper Ltd | Arts & recreation | 2024 |
| J Loading Construction Ltd | Construction | 2025 |
| J M M Sports Ltd | Transport & logistics | 2025 |
| J MAX Consulting Limited | Administrative & support | 2017 |
| J Murphy & Sons of Shirley Ltd | Construction | 2009 |
| J O Plumbing and Heating Ltd | Construction | 2017 |
| J P Developments and Rentals Ltd | Construction | 2019 |
| J P Noel-Cephise Limited | Professional & scientific | 2013 |
| J P Slater Properties Ltd | Real estate | 2022 |
| J Preedy Ltd | Professional & scientific | 2024 |
| J Robinson Pharmacies Limited | Health & social care | 2006 |
| J S M Holdings Limited | Real estate | 1983 |
| J S Miami Ltd | Hospitality | 2016 |
| J T Forry Housing Projects Ltd | Real estate | 2020 |
| J Tailor Optics Ltd | Wholesale & retail | 2024 |
| J Tang Actuarial Limited | Professional & scientific | 2024 |
| J Urquhart Limited | Education | 2017 |
| J&A Waste Removals Ltd | Water & waste | 2022 |
| J&E Construction Ltd | Construction | 2021 |
| J&E Home Care Group Ltd | Health & social care | 2025 |