| Ince Financial Advisory Services Ltd | Professional & scientific | 2021 |
| Indigo UK Bidco Limited | Financial services | 2024 |
| Ineeda Limited | Information & communication | 2025 |
| Infoteam Group Limited | Manufacturing | 1998 |
| Infoteam International Services Limited | Manufacturing | 1997 |
| Ingleside 4, Upper Brighton Road (Surbiton) Residents Association Limited | Households | 1974 |
| Inkling Partnership LLP | | 2011 |
| Inner Balance Ltd | Health & social care | 2024 |
| Inside Football Service Ltd | Financial services | 2023 |
| Insta Services Limited | Administrative & support | 2015 |
| Integrated Climate Solutions Ltd. | Construction | 2016 |
| Integrobuild Ltd | Construction | 2026 |
| Intelligent Security Limited | Manufacturing | 1992 |
| Interastral Peace Corporation Ltd | Wholesale & retail | 2024 |
| Interlinked Solutions Ltd | Professional & scientific | 2020 |
| Ipsum Developments Limited | Construction | 2003 |
| Iqt-Consulting Limited | Professional & scientific | 2011 |
| Ired UK Limited | Administrative & support | 2005 |
| IRF Cable Installations Limited | Professional & scientific | 2011 |
| IT Framework Solutions Limited | Information & communication | 2012 |
| IT Hub International Limited | Real estate | 2021 |
| ITS a Beautiful Life Ltd | Education | 2020 |
| J E a K S Service Limited | Construction | 2014 |
| J G Air Conditioning Limited | Construction | 2001 |
| J P R Installations Ltd | Construction | 2011 |
| J Radford and Sons Ltd | Construction | 2023 |
| J Wyns Limited | Wholesale & retail | 2015 |
| J&D Technology Ltd | Construction | 2016 |
| J&E Food and Wine Limited | Wholesale & retail | 2019 |
| J&J Rental Ltd | Real estate | 2018 |
| J.Thanya Ltd | Hospitality | 2020 |
| J4 Motors Trading Ltd | Wholesale & retail | 2017 |
| JA2 Ltd | Administrative & support | 2014 |
| Jacbo Properties Ltd | Real estate | 2024 |
| Jackson Wardrobes Ltd | Wholesale & retail | 2021 |
| Jacksons (Clear Glass) Holdings Limited | Financial services | 2002 |
| Jacksons (Clear-Glass) Limited | Hospitality | 1945 |
| Jacksons Trustees Limited | Other services | 2022 |
| JAI Ambama Ltd | Construction | 2019 |
| James Family Care Ltd | Health & social care | 2020 |
| James Mccarthy Services Limited | Professional & scientific | 2003 |
| James Whurr Financial Services Limited | Financial services | 2022 |
| Jamp Limited | Real estate | 2005 |
| Jane and Zlatan Swim School Ltd | Arts & recreation | 2020 |
| Janet Smith Tours Limited | Administrative & support | 1988 |
| Janet Smith Travel Limited | Professional & scientific | 2005 |
| Jarellm Ltd | Health & social care | 2023 |
| Jarus KPN Ltd | Wholesale & retail | 2021 |
| JB Cadworx Ltd | Professional & scientific | 2012 |
| JBT Contractor Limited | Construction | 2025 |
| JCC Hammersmith 26 Ltd | Real estate | 2026 |
| JCC Hammersmith Ltd | Real estate | 2026 |
| JCM Star Ltd | Wholesale & retail | 2022 |
| JDC Tiling Ltd | Administrative & support | 2009 |
| JDG Management Consultancy Ltd | Professional & scientific | 2011 |
| JEB Studio Ltd | Wholesale & retail | 2021 |
| Jebair Ltd | Wholesale & retail | 2025 |
| Jepit Limited | Other services | 2012 |
| Jerk & Serve Limited | Hospitality | 2018 |
| Jester Williams Horse Supplies Limited | Wholesale & retail | 2018 |
| JGS Football Club Ltd | Education | 2021 |
| Jiny Ltd | Other services | 2005 |
| Jjhan Ltd | Hospitality | 2023 |
| JKG Dentart Studio Ltd | Administrative & support | 2015 |
| Jkwinner Limited | Wholesale & retail | 2015 |
| JMC Europe Limited | Information & communication | 2007 |
| Joii Sushi Limited | Manufacturing | 2019 |
| Joinery Support Solution Ltd | Manufacturing | 2013 |
| Jones Bros Real Estate Ltd | Real estate | 2022 |
| Joseph Property Maintenance Ltd | Households | 2025 |
| Josh Bamber Limited | Information & communication | 2017 |
| JS Trading Europe Ltd | Wholesale & retail | 2020 |
| Juha Polymers Ltd | Manufacturing | 2024 |
| Jullie Trading Ltd | Wholesale & retail | 2012 |
| Just Zeno Ltd | Information & communication | 2026 |
| Justice Sports Ltd | Wholesale & retail | 2014 |
| JW Pinnacle Properties Co Ltd | Real estate | 2015 |
| JWC Electrical Ltd | Construction | 2015 |
| Jworks Trading Ltd | Wholesale & retail | 2016 |
| K J Restaurant Ltd. | Hospitality | 2004 |
| K Plasters Ltd | Construction | 2016 |
| K&K Building & Construction Ltd | Construction | 2020 |
| K. C. Chessington Limited | Hospitality | 1996 |
| K.Bap BBQ Restaurant Ltd | Hospitality | 2019 |
| KA Ichigo Ltd | Wholesale & retail | 2018 |
| Kaizen Entertainment Limited | Manufacturing | 2020 |
| Kappasushi Ltd | Hospitality | 2019 |
| Karbon Kinetics Ltd | Professional & scientific | 2002 |
| Kashmesh Trading Ltd | Construction | 2018 |
| Kaztech Solutions Ltd. | Information & communication | 2013 |
| Kbap Express Ltd | Hospitality | 2023 |
| KCH Learning Limited | Education | 2024 |
| KCS Crane & Transport Services Ltd | Transport & logistics | 2016 |
| KD Business Tour Ltd | Administrative & support | 2017 |
| KD Nexus Ltd | Real estate | 2024 |
| Kdeu Ltd | Hospitality | 2012 |
| Keane Surveying Limited | Professional & scientific | 2015 |
| KELZER82 Limited | Other services | 2019 |
| Key Asbestos Services Limited | Water & waste | 2006 |
| Keystone Sliverwood Consulting Limited | Information & communication | 2025 |