| Ivanovitch Consulting Ltd | Information & communication | 2023 |
| Ivel Chase Management Company Limited | Households | 2018 |
| Ivinghoe Construction Limited | Construction | 2011 |
| Ivinghoe Golf Club Limited | Arts & recreation | 2011 |
| Ivory and Sage Services Limited | Administrative & support | 2025 |
| Ivory London Limited | Information & communication | 2011 |
| Ivory Media Solutions Ltd. | Information & communication | 2018 |
| IWG Partnership Limited | Professional & scientific | 2016 |
| J & J Design System Specialists Limited | Construction | 1991 |
| J & N Carpentry Ltd | Manufacturing | 2022 |
| J H Wholesale Ltd | Wholesale & retail | 2025 |
| J J Lynch Ground Works Limited | Construction | 2016 |
| J Rowland Ltd | Administrative & support | 2015 |
| J Ryan & Sons Brickwork Ltd | Construction | 2024 |
| J S Copeman Ltd | Construction | 2026 |
| J&J Auto Service Limited | Wholesale & retail | 2024 |
| J&L Gardiner Medical Limited | Health & social care | 2019 |
| J'Bomae Ltd | Real estate | 2021 |
| J.J. Electrical & Telecoms Ltd | Information & communication | 2018 |
| J.R.S. Contracting Limited | Construction | 2007 |
| J666 Ltd | Real estate | 2022 |
| JA Rooflights Limited | Construction | 2023 |
| Jacey Landscaping and Garden Services Ltd | Administrative & support | 2015 |
| Jack Green GEO Ltd | Professional & scientific | 2023 |
| Jack Lane Carpentry Ltd | Manufacturing | 2024 |
| Jadwanda Ltd | Professional & scientific | 2026 |
| Jagadh Validation Services Ltd | Information & communication | 2023 |
| Jake Cummings Ltd | Financial services | 2026 |
| JAM Advisors Limited | Financial services | 2008 |
| JAM Crackers Connect Limited | Information & communication | 2026 |
| JAM Crackers Ltd | Information & communication | 2011 |
| JAM JAR IT Consulting Ltd | Information & communication | 2015 |
| James Harley Consultancy Limited | Information & communication | 2022 |
| James J Burr Ltd | Professional & scientific | 2025 |
| James T Whitaker (Fork Truck Training) Limited | Administrative & support | 1998 |
| Jameson Consulting Ltd | Information & communication | 2024 |
| Janani Maternity Wear Limited | Wholesale & retail | 2025 |
| Jandel Engineering Limited | Manufacturing | 1967 |
| Jane Clements Consultancy Ltd | Real estate | 2026 |
| Jane Houghton Consulting Ltd | Professional & scientific | 2015 |
| Jarem Accountancy Services Limited | Professional & scientific | 2011 |
| Jasmine Gartner Consulting Ltd | Professional & scientific | 2019 |
| Jaxell Ltd | Professional & scientific | 2018 |
| Jazz Transport Ltd | Wholesale & retail | 2018 |
| JB18 Ltd | Construction | 2021 |
| JBL Engineers Limited | Professional & scientific | 2016 |
| JBL Technologies Ltd | Professional & scientific | 2026 |
| JC Fashion (UK) Company Limited | Wholesale & retail | 2014 |
| JC Film Consultancy Limited | Information & communication | 2015 |
| JCT 1 Ltd | Administrative & support | 2012 |
| JD & ND Property Investments Limited | Real estate | 2019 |
| JD Global Management Ltd | Professional & scientific | 2017 |
| JD Mpouki Taxi Services Limited | Transport & logistics | 2016 |
| JD Paintworx Limited | Wholesale & retail | 2020 |
| Jd.Entertainers Ltd | Administrative & support | 2024 |
| JDB Consulting Ltd. | Arts & recreation | 2016 |
| JDB Electrics Limited | Construction | 2025 |
| JDT Hamblin Limited | Construction | 2016 |
| Jebech Developments Limited | Construction | 2004 |
| Jebs Electrical and Building Services Limited | Manufacturing | 2018 |
| Jensen Villas Limited | Construction | 2021 |
| Jessy Childminding Limited | Health & social care | 2015 |
| JET Bookkeeping Limited | Professional & scientific | 2024 |
| JET VFX Ltd | Information & communication | 2022 |
| Jetgen.Com Limited | Extraterritorial | 2015 |
| Jetstream Projects Ltd | Professional & scientific | 2023 |
| Jett Sport and Play Limited | Education | 2021 |
| Jetz Technical Services Limited | Professional & scientific | 2016 |
| Jewel ADS Ltd | Professional & scientific | 2022 |
| Jeyayogi Ltd | Wholesale & retail | 2024 |
| Jflm Consultants Ltd | Professional & scientific | 2014 |
| JGB Investments Limited | Real estate | 2021 |
| JGE Commercials Investments Holdings Limited | Financial services | 2011 |
| JGE Consulting Ltd | Professional & scientific | 2023 |
| JGE Metals Limited | Wholesale & retail | 1991 |
| JGE Recycling Limited | Water & waste | 2014 |
| JGE Truck & Plant Limited | Wholesale & retail | 2011 |
| JGP Trading Limited | Wholesale & retail | 2022 |
| JH 90 Limited | Hospitality | 2024 |
| Jilany & Brothers Group Ltd | Wholesale & retail | 2024 |
| Jit-Pak Technical Ltd | Manufacturing | 2010 |
| JJ Burr Ltd | Professional & scientific | 2015 |
| JJG Property Ltd | Construction | 2020 |
| JK Inspection Services Limited | Construction | 2014 |
| JK K9 Security Ltd | Other services | 2016 |
| JK Wine Consultancy Ltd | Wholesale & retail | 2020 |
| Jkkt Creative Limited | Arts & recreation | 2010 |
| JKP Real Estate Ltd | Real estate | 2020 |
| JL Contracting Ltd | Information & communication | 2026 |
| JLA Enterprises Ltd | Information & communication | 2015 |
| JLJ Mediation Limited | Professional & scientific | 2012 |
| JMG Studio Limited | Arts & recreation | 2019 |
| JML Books Ltd | Wholesale & retail | 2023 |
| JMS Pro Heating and Plumbing Ltd | Construction | 2019 |
| Jmsyoga Ltd | Arts & recreation | 2024 |
| JMT Holdings (Cades) Limited | Professional & scientific | 2020 |
| JN Bookkeeping and Consultancy Ltd | Professional & scientific | 2024 |
| JNO Real Estate Ltd | Real estate | 2022 |
| JO Starbooks Limited | Wholesale & retail | 2023 |
| Joana Kramo Limited | Health & social care | 2019 |