| Janes Pantry Limited | Wholesale & retail | 2003 |
| Janet Davies Funeral Services Limited | Extraterritorial | 2007 |
| Janet Dobson Design Limited | Other services | 2013 |
| Jangeisdomain Ltd | Manufacturing | 2020 |
| Janiivec Forecourt Services Ltd | Wholesale & retail | 2020 |
| Janiivec Ltd | Wholesale & retail | 2016 |
| Janivec Retails Ltd | Wholesale & retail | 2017 |
| Janrozina Ltd | Wholesale & retail | 2020 |
| Janus Corporate Advisers Limited | Professional & scientific | 2025 |
| Janus Property Investment (Inworth) Limited | Real estate | 2013 |
| JAP Contracts Limited | Extraterritorial | 1995 |
| Jarlin Healthcare Services Limited | Health & social care | 2016 |
| Jarman Consulting Ltd | Information & communication | 2024 |
| Jarman Investments Ltd | Real estate | 2019 |
| JAS EGY Ltd | Wholesale & retail | 2019 |
| Jasmine Place Experience Limited | Hospitality | 2016 |
| Jasmy Limited | Health & social care | 2016 |
| Jason Cater Consulting Limited | Professional & scientific | 2018 |
| Jason Nichols Haulage Limited | Transport & logistics | 2025 |
| Jatonel Ltd | Real estate | 2026 |
| Jatt Advisory Limited | Construction | 2023 |
| Jattanjie Ltd | Health & social care | 2024 |
| Jawman Busines and Services Ltd | Administrative & support | 2025 |
| JAY Childcare Matters Ltd | Administrative & support | 2011 |
| JAY Express Ltd | Wholesale & retail | 2021 |
| JAY Jay’S Healthcare Ltd | Health & social care | 2019 |
| Jayaleela Services Ltd | Wholesale & retail | 2023 |
| Jaygate Developments Limited | Real estate | 1995 |
| Jaynam Security Ltd | Administrative & support | 2023 |
| Jaysrays Limited | Other services | 2004 |
| JAZ Business Solutions Ltd | Other services | 2020 |
| JAZ Wiggins Contractor Ltd | Construction | 2021 |
| Jazmin Kerins Ltd | Professional & scientific | 2024 |
| JB 3D Limited | Information & communication | 2014 |
| JB and EP Property Ltd | Real estate | 2025 |
| JB Carpentry (Essex) Ltd | Construction | 2018 |
| JB Heating and Plumbing Services Ltd | Professional & scientific | 2022 |
| JBC Building & Carpentry Contractors Ltd | Construction | 2021 |
| JBS Property Renovations Limited | Construction | 2020 |
| Jbtmo Ltd | Administrative & support | 2017 |
| JBW Services Ltd | Other services | 2021 |
| JC & SM James Properties Limited | Real estate | 2014 |
| JC Aerial School Limited | Arts & recreation | 2020 |
| JC Carter Ltd | Financial services | 2025 |
| JC Furniture Repairs Ltd | Other services | 2016 |
| JCB Construction Services Limited | Construction | 2008 |
| JCD Tech Services Ltd | Professional & scientific | 2015 |
| JCD Touring Ltd | Administrative & support | 2021 |
| JCH Contracts UK Limited | Construction | 1998 |
| JCI Projects Ltd | Construction | 2017 |
| JCJ Electrics Limited | Construction | 2010 |
| JCJ Group Holdings Limited | Financial services | 2023 |
| JCJ Land Management Limited | Real estate | 2023 |
| JCM Care Services Limited | Administrative & support | 2021 |
| JCP Auto Restoration Limited | Wholesale & retail | 2015 |
| JCR Pharma Ltd | Professional & scientific | 2022 |
| JCT Tiling Limited | Construction | 2023 |
| Jctw Ltd | Transport & logistics | 2022 |
| Jcwaves Limited | Professional & scientific | 2025 |
| JD Animal Fitness and Rehab Ltd | Professional & scientific | 2023 |
| JD Bars and Leisure Limited | Hospitality | 2025 |
| JD Electrical (Essex) Ltd | Construction | 2019 |
| JD Health & Safety Ltd | Public administration | 2013 |
| JD Parking Solutions Ltd | Professional & scientific | 2021 |
| JDC Controls Ltd | Manufacturing | 2006 |
| Jdewood Ltd | Health & social care | 2020 |
| JDF Consulting and Management Limited | Professional & scientific | 2018 |
| JDF Property Limited | Real estate | 2018 |
| JDH Luxury Lifestyle Ltd | Other services | 2024 |
| JDL Aviation Ltd | Transport & logistics | 2021 |
| JDM Consulting & Sales Ltd | Wholesale & retail | 2019 |
| JDM Property Limited | Real estate | 2020 |
| JDP Carpentry and Building Services Limited | Construction | 2024 |
| JDS Contractor Services Limited | Construction | 2012 |
| JDS Haran Ltd | Real estate | 2016 |
| JDV Construction Group Ltd | Construction | 2024 |
| Jean Allen Care Services Limited | Health & social care | 2008 |
| Jean Cullen Ltd | Professional & scientific | 2017 |
| Jeb-Nl Holdings Ltd | Wholesale & retail | 2026 |
| Jebrielle Health Services Ltd | Health & social care | 2020 |
| JEC Construction Ltd | Construction | 2016 |
| Jeccl Limited | Information & communication | 2018 |
| JED Company Ltd | Administrative & support | 2018 |
| JED Hub Ltd | Education | 2024 |
| JED Wine Consultancy Limited | Professional & scientific | 2017 |
| Jedd Limited | Professional & scientific | 2018 |
| Jedd Pack and Solutions Ltd | Professional & scientific | 2026 |
| Jeeparts-Uk Ltd | Other services | 2017 |
| Jeet Limited | Real estate | 1996 |
| JEF Kitchens & Bedrooms Ltd | Manufacturing | 2022 |
| Jefferson Filho Ltd | Information & communication | 2026 |
| Jeffery Investments Limited | Professional & scientific | 1995 |
| Jeffs Construction Ltd | Construction | 2013 |
| JEJ Holdings Limited | Real estate | 2023 |
| JEJ Properties Limited | Real estate | 2024 |
| JEM Brickwork (Essex) Limited | Construction | 2021 |
| JEM Smart Limited | Professional & scientific | 2007 |
| JEM UK Associates Ltd | Administrative & support | 2014 |
| Jemina & Co Ltd | Information & communication | 2019 |
| Jemuk Recruitment Ltd | Other services | 2020 |