| Isys Integrity Limited | Professional & scientific | 2009 |
| IT Support Plus London Limited | Wholesale & retail | 2018 |
| IT Virtualisation and Storage Consultancy Ltd | Information & communication | 2014 |
| It's Contained Ltd | Hospitality | 2020 |
| Italiano’S Pizza Ltd | Hospitality | 2021 |
| Itzkintokunbo Limited | Wholesale & retail | 2023 |
| Ivgo Properties Ltd | Real estate | 2024 |
| IVI Alltask Ltd | Construction | 2025 |
| Ivster Ltd | Real estate | 2023 |
| IYE WIN Ltd | Wholesale & retail | 2021 |
| J & B Harty Enterprises Limited | Financial services | 2015 |
| J & C International Trading Co., Ltd | Wholesale & retail | 2023 |
| J & J Roofing Ltd | Construction | 2020 |
| J & S Developments (Kent) Ltd | Real estate | 2013 |
| J BEE Beauty Limited | Other services | 2023 |
| J D Bookkeeping Limited | Professional & scientific | 2004 |
| J Deans Plastering Contractors Limited | Construction | 2004 |
| J Fuller & SON Surfacing Ltd | Construction | 2026 |
| J K Developments and Investments Limited | Real estate | 2017 |
| J K Electrics Ltd | Construction | 2007 |
| J K Safety Training Limited | Education | 2015 |
| J Molski Engineering Ltd | Construction | 2007 |
| J Monks Property Services Ltd | Construction | 2025 |
| J P C Surfacing Limited | Other services | 2015 |
| J P J Properties Limited | Real estate | 1999 |
| J P R Construction Ltd | Construction | 2017 |
| J Spensley Limited | Administrative & support | 2012 |
| J White Mechanical Limited | Construction | 2017 |
| J&D Project Management Limited | Professional & scientific | 2022 |
| J&G Spares & Services Limited | Construction | 2011 |
| J&J International Consultants Ltd | Information & communication | 2023 |
| J&J International Ltd | Information & communication | 2023 |
| J&Jmomo Limited | Wholesale & retail | 2025 |
| J. Walker Cars Limited | Wholesale & retail | 1989 |
| J.A.D. Associates Limited | Professional & scientific | 1989 |
| J.A.Glover Limited | Manufacturing | 1977 |
| J.J. Euro Engineering (Sittingbourne) Limited | Professional & scientific | 1973 |
| J.J.'s Country Activities Limited | Education | 2022 |
| J.Lee Plumbing and Heating Ltd | Construction | 2026 |
| J.Marks Conversions Ltd | Construction | 2019 |
| J.P. Knight & Sons Limited | Wholesale & retail | 2003 |
| J.P.Austin Consultant Ltd | Professional & scientific | 2025 |
| J.S Real Estate Ltd | Real estate | 2018 |
| J.T Groundworks Limited | Construction | 2005 |
| Ja&La Ltd | Wholesale & retail | 2023 |
| Jabang Solutions Ltd | Health & social care | 2013 |
| Jack Cheng Engineering Mechanical Ltd | Wholesale & retail | 2023 |
| Jack Miller Mortgages Ltd | Financial services | 2024 |
| Jackie Filmer Catering Limited | Hospitality | 2006 |
| Jackson Capital Investments Ltd | Real estate | 2022 |
| Jackson Sustainable Development Group Ltd | Construction | 2020 |
| Jackson's Miniatures Limited | Wholesale & retail | 2002 |
| Jacksons Estate Agents Limited | Real estate | 2000 |
| Jacksons' Jerk Joint Ltd | Hospitality | 2024 |
| Jacobs Ronnie Events Entertainment and Productions Limited | Information & communication | 2018 |
| JAD Accountants Limited | Extraterritorial | 2019 |
| JAD Properties Rainham Limited | Real estate | 2002 |
| Jadaudit Limited | Professional & scientific | 1998 |
| Jadeb Plumbing & Heating Limited | Construction | 2012 |
| Jadi Euro Limited | Hospitality | 2013 |
| Jaem (London) Limited | Other services | 2012 |
| Jaer Property Group Limited | Construction | 2025 |
| Jaer Property Management Limited | Real estate | 2025 |
| JAG Mechanical Building Services Limited | Construction | 2017 |
| JAI SAI Properties Limited | Real estate | 2023 |
| JAJ Portfolio Limited | Real estate | 2020 |
| JAK Media Limited | Professional & scientific | 2025 |
| Jake Rushmere Limited | Manufacturing | 2023 |
| James & Co Fine Jewellers Ltd | Manufacturing | 2026 |
| James Cale Estate Agency Limited | Real estate | 2024 |
| James Frederick Framing Limited | Professional & scientific | 2010 |
| James Hemsworth Limited | Construction | 2014 |
| James Nicholas International Removals Ltd | Transport & logistics | 1998 |
| James Wellesley Limited | Manufacturing | 2015 |
| Jamie Slimmon Ltd | Arts & recreation | 2021 |
| Jamie Weller Financial Services Limited | Financial services | 2013 |
| Janet Medical Services Limited | Health & social care | 2010 |
| Janick Ltd | Hospitality | 2018 |
| Janubian Enterprises Limited | Health & social care | 2015 |
| Jari Group Limited | Real estate | 2024 |
| Jarvis Holdings (Medway) Limited | Real estate | 2008 |
| Jarvis Residential (Medway) Limited | Real estate | 2016 |
| JAS Formworks Limited | Construction | 2015 |
| Jason Mead Car Sales Limited | Wholesale & retail | 1991 |
| Jat-Surv Ltd | Professional & scientific | 2019 |
| Jayasuriya Ltd | Professional & scientific | 2003 |
| Jaybe Services Ltd | Construction | 2019 |
| Jaybee Projects Ltd | Manufacturing | 2025 |
| Jayne Wildish Ltd | Professional & scientific | 2024 |
| Jayrience Ltd | Hospitality | 2024 |
| Jaystech Limited | Administrative & support | 2023 |
| Jaysun Ltd | Wholesale & retail | 2023 |
| JB & Caro Limited | Wholesale & retail | 2019 |
| JB Car Sales Limited | Wholesale & retail | 2014 |
| JB Estate Management Limited | Hospitality | 2020 |
| Jbcs Kent Limited | Administrative & support | 2025 |
| JBM Coffeehouses Limited | Hospitality | 2020 |
| JBR Carpentry Limited | Manufacturing | 2026 |
| Jbuk Ltd | Professional & scientific | 2025 |
| JC Holdings Horsham Ltd | Hospitality | 2025 |