| Innovacare Solutions Limited | Administrative & support | 2025 |
| Inserco Industrial (Controls) Limited | Energy | 2003 |
| Inserco Industrial Holdings Limited | Financial services | 2014 |
| Insight Support Services Limited | Education | 2023 |
| Integral Info Solutions Ltd | Information & communication | 2019 |
| Integral Security Solutions Ltd | Administrative & support | 2016 |
| Inter-Fret Consolidators PVT Ltd | Wholesale & retail | 2018 |
| Intercity Fibre Limited | Construction | 2022 |
| International College of Contemporary Sciences Ltd | Education | 2025 |
| Intimate Walk Global Ltd | Wholesale & retail | 2024 |
| Intune Property Investment Solutions Limited | Real estate | 2016 |
| ION Tours and Travel Ltd | Hospitality | 2022 |
| Ionel Trans Ltd | Transport & logistics | 2018 |
| Ionut Ciuciuc Ltd | Construction | 2016 |
| Ipex Container Line Ltd | Wholesale & retail | 2010 |
| Iralphlewis Ltd | Information & communication | 2014 |
| Irobun Limited | Health & social care | 2020 |
| Irobun Property Limited | Real estate | 2026 |
| Ironworks Consulting Ltd | Information & communication | 2026 |
| Isha Estates Limited | Real estate | 2020 |
| Isparkle Detailing Ltd | Wholesale & retail | 2023 |
| Isupply International Ltd | Administrative & support | 2025 |
| IT Networks Ltd | Professional & scientific | 2015 |
| IT Solutions Consulting Ltd | Information & communication | 2021 |
| It&T Solution Limited | Information & communication | 2023 |
| It's a Flukie! Creation Ltd | Manufacturing | 2018 |
| Itqan Rany Ltd | Information & communication | 2021 |
| Ivax Properties Ltd | Real estate | 2022 |
| IVO Biogas Limited | Professional & scientific | 2020 |
| IVO Group Ltd | Wholesale & retail | 2015 |
| Ixami Ltd | Wholesale & retail | 2023 |
| Ixra Limited | Information & communication | 2026 |
| Iykeson Enterprise Ltd | Construction | 2017 |
| Iykonic Logistics Limited | Wholesale & retail | 2026 |
| Iyscom Traders Limited | Wholesale & retail | 2024 |
| Iyva Properties Ltd | Real estate | 2025 |
| IZ Traders Limited | Information & communication | 2017 |
| J & R Services Limited | Construction | 2017 |
| J & R Supplies Limited | | 1985 |
| J a Allen Consultancy Services Limited | Professional & scientific | 2016 |
| J Accend Ltd | Professional & scientific | 2016 |
| J S Buckland Building and Maintenance Limited | Construction | 2020 |
| J&D Construct Limited | Construction | 2019 |
| J&G UK Construction Limited | Construction | 2014 |
| J&L Bates Carpentry Limited | Construction | 2022 |
| J&M Suppliers Ltd | Wholesale & retail | 2020 |
| J. Price Heating Ltd | Construction | 2024 |
| J. Willard Healthcare Services Limited | Administrative & support | 2012 |
| Jabar Properties Limited | Real estate | 2019 |
| Jacg MED Ltd | Health & social care | 2026 |
| Jack Clark Rainham Limited | Real estate | 1944 |
| Jackson Reforms Ltd | Construction | 2025 |
| Jackson's Lettings & Sales Ltd | Real estate | 2013 |
| Jaffri Elite Trader Limited | Hospitality | 2024 |
| Jaiv Ltd | Wholesale & retail | 2010 |
| Jake IT Solutions Limited | Professional & scientific | 2018 |
| Jake Samuels Ltd | Construction | 2024 |
| Jamaicanpassion Ltd | Hospitality | 2017 |
| Janakey Ltd | Wholesale & retail | 2018 |
| Jans Services Ltd | Administrative & support | 2017 |
| Japanese Motor Spares Ltd | Other services | 2016 |
| Jardan Decorator Limited | Construction | 2023 |
| JAS Property Development (Kent) Ltd | Construction | 2023 |
| JAY Mataji Property Limited | Real estate | 2020 |
| JAY ZEE Barbers Limited | Other services | 2020 |
| Jayema Brand Ltd | Wholesale & retail | 2023 |
| Jaymedex Ltd | Health & social care | 2023 |
| JAZ Sidhu London Ltd | Manufacturing | 2026 |
| JCG Plumbing Limited | Construction | 2014 |
| JDS N Solutions Limited | Professional & scientific | 2015 |
| Jebkins Limited | Real estate | 2023 |
| Jellyfielder Studios Ltd | Information & communication | 2010 |
| JEN Estates Ltd | Real estate | 2021 |
| JEN Export Limited | Transport & logistics | 2013 |
| JEN Rentals Ltd | Real estate | 2021 |
| Jenluxe London Limited | Wholesale & retail | 2020 |
| Jennifer M Richardson Limited | Professional & scientific | 2001 |
| Jennifer Richardson Payroll & Bookkeeping Services Ltd | Professional & scientific | 2011 |
| Jerk an Ting Limited | Hospitality | 2022 |
| Jethro Integrated Limited | Wholesale & retail | 2024 |
| Jexom Ltd | Real estate | 2024 |
| Jexport Solutions Ltd | Transport & logistics | 2020 |
| JFK Tech Security Ltd | Professional & scientific | 2025 |
| JFK Tech Training Ltd | Education | 2023 |
| JFK Technologies Ltd | Professional & scientific | 2015 |
| JH Foods UK Limited | Wholesale & retail | 2019 |
| JHD International Consultants Ltd | Information & communication | 2019 |
| JHD Properties Management Ltd | Real estate | 2024 |
| Jibran UK Group Limited | Transport & logistics | 2020 |
| Jimkoy Developments Ltd | Real estate | 2025 |
| Jiten Limited | Wholesale & retail | 2006 |
| JJ Barry Conglomarate Limited | Information & communication | 2016 |
| JJ Care Support Solutions Ltd | Health & social care | 2022 |
| JJJ Healthcare Limited | Health & social care | 2023 |
| JJL Builders Limited | Construction | 2022 |
| JK Autos & Tyres Ltd | Wholesale & retail | 2026 |
| Jktg Properties Limited | Real estate | 2017 |
| Jloucis Ltd | Wholesale & retail | 2026 |
| JLR Carpentry Limited | Construction | 2012 |
| JM Builders and Properties Ltd | Construction | 2024 |