| Jayasri Ltd | Information & communication | 2018 |
| JAZ & Josh Limited | Financial services | 2011 |
| Jazaa IT Consultancy Limited | Information & communication | 2017 |
| JB Fine Gardening & Grounds Ltd | Administrative & support | 2026 |
| Jbsa Consulting Limited | Professional & scientific | 2020 |
| JC Scenic Ltd | Construction | 2022 |
| JCG1 Ltd | Information & communication | 2024 |
| JCL Killeen Ltd | Construction | 2026 |
| Jconstructionmiddlesex Limited | Construction | 2014 |
| JCS (DM) Ltd | Administrative & support | 2006 |
| JCS Motor Company Ltd | Wholesale & retail | 2025 |
| JD International Limited | Wholesale & retail | 2015 |
| JD Motor Factors Limited | Extraterritorial | 2016 |
| Jdac Hydroworks Ltd | Construction | 2025 |
| JDM Motor Services Ltd | Wholesale & retail | 2023 |
| JDP Limited | Professional & scientific | 1990 |
| Jeffery Properties Limited | Real estate | 2018 |
| Jegan Retailers Ltd | Wholesale & retail | 2023 |
| Jemelo Consulting Limited | Professional & scientific | 2014 |
| Jengot Ltd | Construction | 2025 |
| Jenjo Ltd | Real estate | 2024 |
| Jenkz Media Limited | Information & communication | 2026 |
| Jer-Med Limited | Financial services | 1973 |
| Jeri Limited | Information & communication | 2010 |
| JES Apartments Limited | Households | 2024 |
| Jesen Ltd | Transport & logistics | 2019 |
| Jessica Lumley Coaching Ltd | Health & social care | 2025 |
| Jessica Pilates Limited | Arts & recreation | 2015 |
| JET Locksmiths Ltd | Manufacturing | 2016 |
| Jewel Maintenance Services Ltd | Manufacturing | 2011 |
| Jezrez Limited | Construction | 2026 |
| JFP Strategic Planning Ltd | Professional & scientific | 2013 |
| JGI Holdings Ltd | Financial services | 2020 |
| JH Aviation Training and Consulting Ltd | Education | 2022 |
| JH Roofline and Cladding Ltd | Construction | 2025 |
| JIA Sports UK Agency Limited | Other services | 2018 |
| Jigsaw Estates Limited | Real estate | 2015 |
| Jigsaw Financial Services Limited | Financial services | 2003 |
| Jimmy Nails Limited | Other services | 2017 |
| Jivegold Limited | Households | 1998 |
| JJ UK Holdings Limited | Financial services | 2022 |
| Jjjn Limited | Information & communication | 2020 |
| JJK Management Consultancy Limited | Professional & scientific | 2006 |
| JK Partnerships Ltd | Construction | 2017 |
| Jk&K Property Ltd | Real estate | 2023 |
| JKV Aviation Ltd | Transport & logistics | 2020 |
| JLA Resourcing Ltd | Administrative & support | 2019 |
| JLH Estates Ltd | Construction | 2022 |
| JM Production Holdings Limited | Arts & recreation | 2023 |
| JMC 271 Limited | Real estate | 2023 |
| JMC Uxbridge Limited | Real estate | 2026 |
| Jmtm International Couriers Limited | Transport & logistics | 2013 |
| JNG Computing Limited | Information & communication | 1996 |
| JNR Developments Limited | Real estate | 2021 |
| JNT Construction Consultants Limited | Professional & scientific | 2020 |
| JNV Properties Ltd | Real estate | 2022 |
| JNV Property Rental Ltd | Real estate | 2024 |
| JOB Box Recruitment Limited | Administrative & support | 2015 |
| Jobeqs Limited | Professional & scientific | 2005 |
| Jocte Ltd | Information & communication | 2011 |
| JOE Storey & Associates Limited | Administrative & support | 1973 |
| Joe's Blooms Ltd | Professional & scientific | 2022 |
| Joel & Jude Ltd | Wholesale & retail | 2020 |
| Joel and Jude Associates Limited | Energy | 2015 |
| JOEROTIMI1962 Limited | Health & social care | 2024 |
| John Amor Consulting Ltd | Professional & scientific | 2017 |
| John Grant Interiors Limited | Construction | 1986 |
| John Hatto Butchers Limited | Wholesale & retail | 2008 |
| John JOE Photography & Video Ltd | Information & communication | 2017 |
| John Payne (Blackheath) Limited | Extraterritorial | 1985 |
| John Payne (Greenwich) Limited | Extraterritorial | 1987 |
| John Payne (LEE) Limited | Extraterritorial | 1985 |
| John Payne (Lettings) Limited | Extraterritorial | 2004 |
| John Payne (Westcombe Park) Limited | Extraterritorial | 1999 |
| John Pegrum French Polisher Ltd | Other services | 2011 |
| Johnanda Holdings Limited | Real estate | 2015 |
| Johnnie Gurkha's Limited | Hospitality | 1999 |
| Joint Waste Solutions Limited | Other services | 2017 |
| Jojay Ventures Limited | Health & social care | 2015 |
| Jollymart Ltd | Wholesale & retail | 2023 |
| Jomar SE Engineering Limited | Professional & scientific | 2024 |
| Jomar SE Limited | Professional & scientific | 2016 |
| Jomatt Coaching and Consultancy Ltd | Other services | 2021 |
| Jonathon Cloud Ltd | Wholesale & retail | 2010 |
| Jonnoj Ltd | Information & communication | 2015 |
| Joon Tech Ltd | Information & communication | 2023 |
| Jordan's Residential Lettings Limited | Extraterritorial | 2001 |
| Joslyn Constructions Limited | Construction | 2017 |
| Journey Electronics Ltd. | Extraterritorial | 2016 |
| Jovi Estates Ltd | Households | 2026 |
| Jozi Power Limited | Energy | 2006 |
| Jpca Enterprise Limited | Professional & scientific | 2025 |
| JPT Construction Services Ltd | Other services | 2017 |
| JQ Heating and Plumbing Ltd | Manufacturing | 2020 |
| JR Landscapes and Construction Ltd | Construction | 2024 |
| JS Luxury Real Estate Limited | Extraterritorial | 2021 |
| JSD Development Projects Limited | Construction | 2023 |
| JSD Developments 2 Limited | Construction | 2024 |
| Jsnaoe Services Ltd. | Health & social care | 2020 |
| JSS & Sons Ltd | Professional & scientific | 2013 |