| Jarzish Ltd | Administrative & support | 2024 |
| Jasun Technology Limited | Manufacturing | 1993 |
| Jatie Ltd | Other services | 2013 |
| Javed Care Limited | Health & social care | 2013 |
| Javed Mushtaq Ltd | Administrative & support | 2017 |
| JAY Mila Ltd | Wholesale & retail | 2020 |
| Jaymark Engineering Limited | Construction | 2012 |
| Jazztify Ltd | Transport & logistics | 2019 |
| JB Construction & SON Ltd | Construction | 2017 |
| JC Management Ltd | Hospitality | 2025 |
| Jcor Investments Limited | Other services | 2021 |
| JD Agency Limited | Wholesale & retail | 2011 |
| JD Telecomms Ltd | Information & communication | 2020 |
| JDA Building Contractor Limited | Construction | 2016 |
| JDF Performing Arts College Ltd | Arts & recreation | 2024 |
| Jeacock Developments Limited | Construction | 2005 |
| Jedbray Ltd | Administrative & support | 2007 |
| Jekko Cranes UK Limited | Wholesale & retail | 2024 |
| Jelleymans Security Services Limited | Administrative & support | 2024 |
| JEM Couriers Ltd | Transport & logistics | 2025 |
| Jemanore Ltd | Administrative & support | 2024 |
| Jemaryst Ltd | Administrative & support | 2024 |
| Jeremaih Ltd | Wholesale & retail | 2025 |
| Jesus Street Evangelism Church Outreach Mission for the Socially Excluded Community Interest Company | Other services | 2025 |
| Jewellery by Design Limited | Other services | 1998 |
| JG Heating Ltd | Construction | 2024 |
| JG Savage Ltd | Transport & logistics | 2021 |
| Jhet Ltd | Professional & scientific | 2023 |
| Jhewl Ltd | Households | 2025 |
| JHL Precision Limited | Manufacturing | 2007 |
| Jhotunzic Ltd | Wholesale & retail | 2024 |
| Jidwelliux Ltd | Administrative & support | 2024 |
| Jingjing Property Investment Ltd | Real estate | 2020 |
| Jjbs Consulting Limited | Information & communication | 2025 |
| Jjed Holdings Limited | Administrative & support | 2019 |
| JJJ TM Ltd | Construction | 2023 |
| JK Consultancy Services Limited | Information & communication | 2001 |
| JKK4 Services Ltd | Hospitality | 2025 |
| JL Accountancy and Consulting Limited | Education | 2016 |
| JLC Barbers (UK) Limited | Other services | 2011 |
| JLR Transport Ltd | Transport & logistics | 2023 |
| JM Murdoch Ltd | Transport & logistics | 2025 |
| JM Powell Group Limited | Hospitality | 2024 |
| JMA Consultancy Services Ltd | Professional & scientific | 2024 |
| Jmbarry Group Ltd | Construction | 2026 |
| JMS Rigging Ltd | Information & communication | 2023 |
| Jnml Investments Ltd | Financial services | 2024 |
| John Kingston Limited | Administrative & support | 2005 |
| John S. Leek (International Cars) Limited | Extraterritorial | 1967 |
| John Salters Holdings Limited | Financial services | 2014 |
| John Swift Limited | Real estate | 2018 |
| John Wright Car Repairs Limited | Wholesale & retail | 2003 |
| Johnson Watch Company Ltd | Manufacturing | 2025 |
| Jones Chartered Architects Ltd | Professional & scientific | 2019 |
| Jones Metals Ltd | Water & waste | 2026 |
| Jordan Smart Properties Limited | Real estate | 2024 |
| Jordizy Ltd | Transport & logistics | 2023 |
| Joshua Resourcing Ltd | Professional & scientific | 2016 |
| Joy Ocean Ltd | Wholesale & retail | 2026 |
| Joybrad Ltd | Real estate | 2018 |
| JP Asset Holdings Limited | Real estate | 2024 |
| JP Electrical Contractors (Worcestershire) Ltd | Construction | 2023 |
| JP North Ltd | Hospitality | 2021 |
| Jpclark Limited | Real estate | 2021 |
| Jpmxch Ltd | Other services | 2021 |
| JPS Patterns Limited | Wholesale & retail | 2000 |
| JR Gallagher Services Ltd | Health & social care | 2013 |
| JR Harwood Ltd | Hospitality | 2021 |
| JRB Welding Limited | Construction | 2023 |
| Jrrs Electrics Limited | Administrative & support | 2018 |
| JS Builders Limited | Construction | 2002 |
| JSA Contracts Ltd | Construction | 2024 |
| JT Calvert Ltd | Administrative & support | 2022 |
| JT Telecomms Ltd | Information & communication | 2024 |
| Jtmahoney Ltd | Real estate | 2023 |
| Jubilee Close (Management Company) Limited | Real estate | 2012 |
| Julia Bright Limited | Extraterritorial | 2024 |
| Julia Rosalind Bright Ltd | Extraterritorial | 2022 |
| Juma Escapes Ltd | Hospitality | 2021 |
| Jumberium Ltd | Administrative & support | 2024 |
| Jungle Trader Limited | Wholesale & retail | 2010 |
| Junior Changemakers CIC | Education | 2022 |
| JUNKBUSTERS365 Ltd | Water & waste | 2023 |
| Just AS Business Ltd | Wholesale & retail | 2018 |
| Just the Thing Gift Registry Limited | Wholesale & retail | 2006 |
| Jute Products Ltd | Wholesale & retail | 2022 |
| JWC Birmingham Limited | Professional & scientific | 2019 |
| JY Tait Ltd | Transport & logistics | 2021 |
| JZA Properties Ltd | Real estate | 2025 |
| K a & T a Hudson Limited | Construction | 2011 |
| K C Dust and Shine Cleaning Services Limited | Administrative & support | 2023 |
| K L Phillips Limited | Administrative & support | 2020 |
| K P L UK Limited | Construction | 2003 |
| K Phillips Landscaping Limited | Construction | 2019 |
| K R Care Ltd | Health & social care | 2013 |
| K R Securities Limited | Administrative & support | 2013 |
| K S Autos Midlands Ltd | Wholesale & retail | 2026 |
| K S Jones & Sons Limited | Transport & logistics | 2019 |
| K T Barrett Construction & Landscapes Ltd | Construction | 2019 |
| K T F Services Ltd | Transport & logistics | 2015 |