| J. Silk Agricultural Co. Ltd | Manufacturing | 2013 |
| J.A.B. Technical Services Limited | Manufacturing | 2005 |
| J.E Builders Ltd | Construction | 2021 |
| J.E.S Healthcare Ltd | Health & social care | 2013 |
| J.M Building Improvements Ltd | Construction | 2022 |
| J.M. Godfrey Landscapes Limited | Administrative & support | 2005 |
| J.R.C. Newton & Partners Limited | Real estate | 1978 |
| J.Worley (Funeral Directors) Limited | Other services | 1984 |
| J2S Associates Limited | Real estate | 2019 |
| Jaaze Ltd | Wholesale & retail | 2025 |
| Jack Barbering Ltd | Other services | 2026 |
| Jack Fymruk Property Ltd | Extraterritorial | 2022 |
| Jackets Bags and Balls Limited | Wholesale & retail | 1999 |
| Jackob Ltd | Transport & logistics | 2018 |
| Jackson Facilities Management Ltd | Administrative & support | 2025 |
| Jackson Green Recruitment Limited | Administrative & support | 2016 |
| Jackson Property Services London Ltd | Construction | 2023 |
| Jackweld Limited | Construction | 2006 |
| Jacob Ross Holdings Limited | Real estate | 2020 |
| Jactwist Coffeefix Limited | Manufacturing | 2008 |
| Jafra Logistics Ltd | Construction | 2025 |
| Jago Steel Ltd | Construction | 2020 |
| Jaigro Holdings Limited | Real estate | 2026 |
| Jakubik Ltd | Transport & logistics | 2014 |
| James & Andrew Stoddart Limited | Construction | 1972 |
| James Avenue (Calne) Management Company Ltd | Households | 2021 |
| James Booth Accountancy Ltd | Professional & scientific | 2023 |
| James Cooper VFX Limited | Information & communication | 2017 |
| James Latham (Midland and Western) Limited | Wholesale & retail | 1972 |
| James Latham (Warehousing) Limited | Wholesale & retail | 1977 |
| James Latham Public Limited Company | Wholesale & retail | 1900 |
| James Latham Trustee Limited | Professional & scientific | 1990 |
| James Lewis Property Letting Ltd | Real estate | 2021 |
| James Marks Academy Trust | Education | 2019 |
| James Redmond Ltd | Transport & logistics | 2013 |
| James S Pearce Services Ltd | Information & communication | 2024 |
| Janari Care Limited | Health & social care | 2021 |
| Janwood Ltd | Construction | 2017 |
| Jarman Gates & Railings Limited | Manufacturing | 2009 |
| Jas-Wood Limited | Manufacturing | 2008 |
| Jas.Singh Enterprise Ltd | Construction | 2024 |
| Jaska&Co Ltd | Transport & logistics | 2025 |
| Jasmine and Bluebell Management Company at the Mulberries Limited | Households | 2026 |
| Jason B Logistics Ltd | Wholesale & retail | 2022 |
| Jason B Services Ltd | Transport & logistics | 2020 |
| Jasper Gilder Limited | Professional & scientific | 1995 |
| Jawfray Consult Limited | Other services | 2011 |
| JAY Meladi MA Limited | Financial services | 2004 |
| Jayamber Limited | Information & communication | 2022 |
| Jayme Property Ltd | Real estate | 2024 |
| Jayne Air Ltd | Manufacturing | 2025 |
| JAZ CI Services Limited | Professional & scientific | 2025 |
| JB & NA Motors & Recovery Ltd | Wholesale & retail | 2022 |
| JB Jewellers Ltd | Wholesale & retail | 2019 |
| JB Scenery Construction Ltd | Construction | 2022 |
| JBC Construction Limited | Construction | 2025 |
| JBH Services NE Ltd | Construction | 2025 |
| JBS Landscapes Ltd | Administrative & support | 2025 |
| JBZ Investments Limited | Financial services | 2019 |
| JC Futures Trading Ltd | Financial services | 2024 |
| JC Mortgages Ltd | Administrative & support | 2024 |
| Jccnaccountants Limited | Professional & scientific | 2014 |
| JCD Architectural Ltd | Construction | 2022 |
| JCD Asset Management Ltd | Real estate | 2026 |
| JCD Contractors Ltd | Construction | 2022 |
| JCD Firestopping Ltd | Construction | 2022 |
| JCG Building Services Limited | Construction | 2003 |
| JD Inns Ltd | Hospitality | 2015 |
| JD Marsh Properties Ltd | Real estate | 2024 |
| JD Plastering and Tiling Solutions Ltd | Construction | 2025 |
| JD Scaffolding Specialist Ltd | Construction | 2022 |
| JD Sparks Ltd | Construction | 2016 |
| JDA Estates Limited | Real estate | 2024 |
| JDC AV Limited | Construction | 2026 |
| JDF Network Ltd | Administrative & support | 2008 |
| JDM Subsidiary 1 Limited | Information & communication | 2019 |
| JDM Technology Group Limited | Information & communication | 2006 |
| JDR Tree Care Ltd | Construction | 2017 |
| Jeeb Ltd | Wholesale & retail | 2023 |
| Jegs Darko Partnership LLP | | 2017 |
| JEN Homes Ltd | Real estate | 2013 |
| Jendale Consulting Limited | Real estate | 2016 |
| Jenkins and Jenkins Enterprises Ltd | Other services | 2019 |
| Jenlex Properties Limited | Real estate | 2017 |
| Jennifer Rudd Case Management Services Limited | Health & social care | 2019 |
| Jenudigitech Limited | Other services | 2018 |
| Jerraco Limited | Other services | 2011 |
| Jerram Design Associates Limited | Construction | 2000 |
| Jessica Services Limited | Health & social care | 2023 |
| Jetstream International UK Limited | Other services | 2018 |
| Jetta Consulting Ltd | Professional & scientific | 2019 |
| Jeyathadshajani Limited | Wholesale & retail | 2018 |
| Jeyes Group Limited | Professional & scientific | 2002 |
| Jeysha Retail Limited | Wholesale & retail | 2024 |
| JFL Holdings Limited | Professional & scientific | 2023 |
| JG Shopfitting & Carpentry Ltd | Construction | 2019 |
| JGK Financial Management Ltd | Professional & scientific | 2017 |
| JH Decorating Ltd | Construction | 2016 |
| Jhonata Discounts Limited | Wholesale & retail | 2024 |
| Jigsaw Quality Ltd | Professional & scientific | 2021 |