| Intermarc Logistics Ltd | Transport & logistics | 2011 |
| Intermoves Limited | Professional & scientific | 2009 |
| Internal Audit and Risk Management Consultancy Ltd | Professional & scientific | 2018 |
| International Careers and Entrepreneurs (Icee) Ltd | Administrative & support | 2016 |
| International Distribution Limited | Wholesale & retail | 2018 |
| International Market Assistance Services Limited | Other services | 2000 |
| Interstellar Compliance UK Ltd. | Financial services | 2015 |
| Intralea Limited | Transport & logistics | 2018 |
| Intrepid Financial Solutions Ltd | Financial services | 2025 |
| Introduced Ltd | Wholesale & retail | 2022 |
| Invested Assets Ltd | Real estate | 2021 |
| Investoption Limited | Real estate | 1996 |
| Invicta IP Ltd | Professional & scientific | 2010 |
| Invictus Recruitment Limited | Administrative & support | 2012 |
| Inviewing Ltd | Professional & scientific | 2020 |
| Ionising Software Limited | Information & communication | 2020 |
| Iotk CIC | Health & social care | 2026 |
| IP and TP Ltd | Professional & scientific | 2025 |
| IPP2 Limited | Real estate | 2020 |
| Iroaganachi and Iroaganachi Solicitors Ltd | Professional & scientific | 2025 |
| Iron Maidens Limited | Extraterritorial | 2007 |
| Ironkookie Ltd | Wholesale & retail | 2022 |
| Ironstax Limited | | 2009 |
| Ironstone Bookkeeping & Consultancy Ltd | Professional & scientific | 2021 |
| Isaac Moore Property Limited | Real estate | 2024 |
| Isboat Limited | Real estate | 2018 |
| Island Fish & Chips Kent Ltd | Hospitality | 2022 |
| Isufov Trade Ltd | Other services | 2016 |
| IT & Engineering Solutions Limited | Information & communication | 2014 |
| IT Capital Services Ltd | Information & communication | 2018 |
| IT Management Consulting Ltd | Other services | 2015 |
| IT Support (UK) Limited | Information & communication | 2010 |
| IT Transport & Logistics Limited | Transport & logistics | 2011 |
| IT UK Service Ltd | Information & communication | 2016 |
| IT Wired Ltd | Wholesale & retail | 2017 |
| Itmetrics Ltd | Information & communication | 1992 |
| Itmp Ltd | Information & communication | 2016 |
| ITP Select Ltd | Administrative & support | 2008 |
| ITS Insured Limited | Financial services | 2022 |
| Itsm Consult Ltd | Information & communication | 2022 |
| Itsverdure Ltd | Real estate | 2012 |
| Iventu Ltd | Professional & scientific | 2021 |
| Iveson & Sons Ltd | Real estate | 2021 |
| Iview Prism Ltd | Wholesale & retail | 2015 |
| Ivory Touch Ltd | Wholesale & retail | 2025 |
| Iwari Limited | Construction | 2024 |
| IYA Ibeji Kitchen (IBK) Catering Services Ltd | Hospitality | 2019 |
| Iyanu Ltd | Arts & recreation | 2020 |
| Iyard Ltd | Real estate | 2020 |
| Izla Laser Limited | Other services | 2025 |
| J & G Financials Limited | Financial services | 2017 |
| J & M Nails Limited | Other services | 2019 |
| J & P Atkins (Developments) Limited | Real estate | 2018 |
| J Ashby Roofing Ltd | Construction | 2007 |
| J Atkins (Properties) Limited | Real estate | 1984 |
| J Ayre (Eltham) Limited | Wholesale & retail | 2015 |
| J C Digital Services Ltd | Information & communication | 2016 |
| J C Elango Ltd | Health & social care | 2022 |
| J Collins Roofing Ltd | Construction | 2025 |
| J Cronin Roofing & Guttering Ltd | Construction | 2026 |
| J Devonshire PR Ltd | Professional & scientific | 2013 |
| J G & P B Estate Limited | Real estate | 2025 |
| J J Brooks Construction Limited | Construction | 1995 |
| J J Mekkatt UK Ltd | Professional & scientific | 2010 |
| J L B Redwood Builder Ltd | Manufacturing | 2026 |
| J Long Property Limited | Real estate | 2019 |
| J M Drewett Property Solutions Ltd | Real estate | 2021 |
| J M Llewellyn (Holdings) Ltd | Financial services | 2018 |
| J Medica Ltd | Health & social care | 2010 |
| J Munro Property Maintenance Limited | Construction | 2002 |
| J P H Floors Limited | Construction | 2009 |
| J Silvester & Sons Building & Maintenance Limited | Construction | 2022 |
| J&C Info Ltd | Information & communication | 2011 |
| J&E Optical Services Ltd | Wholesale & retail | 2023 |
| J&F Decoatings Ltd | Manufacturing | 2019 |
| J&I Contracts Ltd | Information & communication | 2018 |
| J&J Mechanical Services Ltd | Construction | 2025 |
| J&P Group Limited | Hospitality | 2024 |
| J. Southam Fencing & Landscapes Ltd | Administrative & support | 2017 |
| J.E.M Construction & Maintenance Ltd | Construction | 2016 |
| J.G.Ware Limited | Construction | 2013 |
| J7 Consultancy Limited | Financial services | 2022 |
| J7 Fire and Security Ltd | Financial services | 2021 |
| Jack Caulfield Tiling Ltd | Construction | 2016 |
| Jackson & Imms Limited | Wholesale & retail | 2013 |
| Jackson Garage Limited | Wholesale & retail | 2015 |
| Jacob Barber 1 Ltd | Other services | 2025 |
| Jade Window Cleaning & Support Services Ltd | Administrative & support | 2014 |
| JAH JAH Ltd | Hospitality | 2021 |
| JAH JAH Margate Ltd | Hospitality | 2023 |
| Jaimee Ltd | Wholesale & retail | 2016 |
| Jaiye International Ltd | Administrative & support | 2026 |
| Jajomiis Investment Limited | Real estate | 2021 |
| Jajomiis Limited | Other services | 2020 |
| JAK Avenue Ltd | Wholesale & retail | 2022 |
| Jakata Bars & Clubs Limited | Hospitality | 2019 |
| Jakhis Limited | Administrative & support | 2005 |
| James Axford Ltd | Professional & scientific | 2008 |
| James Delamare Limited | Construction | 2013 |
| James Gabriel Ltd | Professional & scientific | 2018 |