| Invoicepit App Ltd | Information & communication | 2026 |
| Inyourpostcode Customs Ltd | Professional & scientific | 2026 |
| Iolite Holdings Ltd | Real estate | 2025 |
| Ioniq Solutions Limited | Professional & scientific | 2026 |
| Ionut Car Wash Ltd | Wholesale & retail | 2022 |
| Iosif Vilcec Ltd | Transport & logistics | 2016 |
| Iosiv Transport Limited | Manufacturing | 2025 |
| IOT Academy Limited | Information & communication | 2025 |
| IPH Solutions 2011 Limited | Construction | 2020 |
| Ipower London Ltd | Construction | 2021 |
| IPP Trans Ltd | Transport & logistics | 2019 |
| Iqbalix Construction Ltd | Construction | 2026 |
| Iris Gold Property Ltd | Real estate | 2025 |
| IRL Construction and Maintenance Ltd | Construction | 2026 |
| Irmak Fast Food Ltd | Hospitality | 2019 |
| Irmat Transport Ltd | Transport & logistics | 2022 |
| Iron PUB Company Ltd | Hospitality | 2018 |
| Ironbar Ltd | Professional & scientific | 2015 |
| Ironchef Ltd | Hospitality | 2026 |
| Irzum Hub Ltd | Wholesale & retail | 2025 |
| Isaac Eugene Onyango Omondi Acca CIA Ltd | Information & communication | 2025 |
| Isave UK Limited | Real estate | 2026 |
| Iscu Trans Limited | Transport & logistics | 2016 |
| Isip Logistics Ltd | Transport & logistics | 2025 |
| Islam Estate Ltd | Real estate | 2024 |
| ISM Auto Repairs Ltd | Wholesale & retail | 2020 |
| Ismah Hair & Cosmetic Ltd | Wholesale & retail | 2020 |
| ISO Contractors Limited | Construction | 2014 |
| Israr Ibaad Limited | Wholesale & retail | 2023 |
| Istorm Limited | Information & communication | 2004 |
| Isufi Teaching Classes Limited | Education | 2025 |
| It's NOT Over YET C.I.C. | Health & social care | 2023 |
| ITC Digital Ltd | Administrative & support | 2008 |
| Itcare Ltd | Information & communication | 2022 |
| Itdedon Limited | Construction | 2025 |
| Itechnick Ltd | Wholesale & retail | 2023 |
| ITM Brickwork Ltd | Construction | 2022 |
| Itnetworksacademy Limited | Education | 2021 |
| ITS Deals Limited | Wholesale & retail | 2019 |
| Iulia Cretu Ltd | Health & social care | 2023 |
| Iulian Speeed TM Ltd | Transport & logistics | 2025 |
| Ivanov & Sons Logistics Ltd | Transport & logistics | 2019 |
| Ivape Grays Ltd | Wholesale & retail | 2020 |
| Ivoryrose Cleaning Services Ltd | Other services | 2013 |
| Ivoryrose Company Limited | Real estate | 2018 |
| Ivoryrose Hospitality Services Limited | Administrative & support | 2017 |
| IVY Nails 68E Limited | Other services | 2026 |
| Iwpat Logistics Ltd | Transport & logistics | 2016 |
| Izzy Logic Limited | Information & communication | 2023 |
| J & D8 Properties Ltd | Real estate | 2025 |
| J & E7 Developments Ltd | Real estate | 2022 |
| J & L Cambridge Limited | Real estate | 2024 |
| J & M Belts Limited | Wholesale & retail | 2002 |
| J a Beard Ltd | Construction | 2024 |
| J Brown Property Devlopment Ltd | Construction | 2017 |
| J D Scarlett Limited | Professional & scientific | 2024 |
| J F Hillebrand (1983) Limited | Transport & logistics | 1983 |
| J Harman Services Ltd | Manufacturing | 2021 |
| J J Piling Ltd | Construction | 2026 |
| J K H Investment Property Ltd | Real estate | 2022 |
| J L P (London) Limited | Arts & recreation | 2014 |
| J S M Haulage Ltd | Transport & logistics | 2012 |
| J S Services Transport Ltd | Transport & logistics | 2018 |
| J&B Paving and Landscaping Ltd | Administrative & support | 2026 |
| J&E Estates Ltd | Real estate | 2024 |
| J&Ht Consulting Ltd | Administrative & support | 2017 |
| J&J Flex Properties Ltd | Real estate | 2025 |
| J&M Safety Services Limited | Administrative & support | 2012 |
| J&T Projects Ltd | Real estate | 2024 |
| J'Adore Properties Ltd | Real estate | 2024 |
| J.& F.May Limited | Construction | 1956 |
| J.C. Brickwork Services Limited | Construction | 2003 |
| J.D.I. Electrical Services Limited | Construction | 2022 |
| J.E. Sharp Developments Limited | Wholesale & retail | 1981 |
| J.K Engineering and Services Ltd | Construction | 2021 |
| J.Okwuazi Limited | Construction | 2015 |
| J.P. Scarlet & Associates Limited | Administrative & support | 2006 |
| J.T.L.Steel Fabrications (U.K.) Ltd | Manufacturing | 2006 |
| J3 Facility Management Solution Limited | Transport & logistics | 2025 |
| J4WARD Global Ltd | Real estate | 2019 |
| Jacdieu Care Services Limited | Health & social care | 2025 |
| Jack Healy Ltd | Construction | 2023 |
| Jackdan Trans Ltd | Transport & logistics | 2023 |
| Jackie Meade Limited | Professional & scientific | 2019 |
| Jacob Sales Ltd | Wholesale & retail | 2023 |
| Jacstar Limited | Professional & scientific | 2014 |
| Jaddu Service Ltd | Transport & logistics | 2026 |
| Jade Medical Services Ltd | Health & social care | 2017 |
| Jades Financial Limited | Professional & scientific | 2021 |
| Jafro Foods Limited | Manufacturing | 2018 |
| JAG Singh Ltd | Information & communication | 2017 |
| Jagajo Ltd | Real estate | 2025 |
| Jaguar Travel Ltd | Administrative & support | 2022 |
| Jahnvi Property Investments Ltd | Real estate | 2025 |
| JAI Lettings Ltd | Real estate | 2024 |
| JAK UK Consulting Ltd | Public administration | 2024 |
| Jalios Limited | Financial services | 2014 |
| JAM Rack Jerk Ltd | Hospitality | 2018 |
| JAM Trans Ltd | Transport & logistics | 2021 |
| Jaman Residence Ltd | Real estate | 2020 |