| James Taylor Group Limited | Professional & scientific | 2015 |
| James Taylor Homes (Brighton) Limited | Construction | 2023 |
| James Taylor Homes (Harrow) Limited | Extraterritorial | 2014 |
| James Taylor Homes (Investment) Limited | Professional & scientific | 2021 |
| James Taylor Homes (Kingston Freehold) Limited | Extraterritorial | 2020 |
| James Taylor Homes (Lincolns Inn Freehold) Limited | Extraterritorial | 2017 |
| James Taylor Homes (Lincolns Inn) Limited | Real estate | 2014 |
| James Taylor Homes (Newton Longville) Limited | Construction | 2020 |
| James Taylor Homes (Slough) Limited | Construction | 2018 |
| James Taylor Homes (Verulamium) Limited | Construction | 2021 |
| James Taylor Homes Group Limited | Professional & scientific | 2016 |
| James Taylor Homes Limited | Extraterritorial | 2008 |
| Jane Johnson & Co. Ltd | Information & communication | 2012 |
| Janet the RN Ltd | Health & social care | 2023 |
| Jano S&Q Fresh Fish Limited | Wholesale & retail | 2024 |
| Jaraf Films Ltd | Information & communication | 2022 |
| JAS Digital Ltd | Wholesale & retail | 2017 |
| Jayjay Communications Limited | Information & communication | 2018 |
| Jayrworks Ltd | Manufacturing | 2025 |
| Jayshree SAI Investments Ltd | Real estate | 2018 |
| JB Aviation Services Ltd | Manufacturing | 2018 |
| JB Plant Services Ltd | Construction | 2020 |
| JC & Sons Scaffolding Services Ltd | Construction | 2024 |
| JC Galanews Limited | Wholesale & retail | 2017 |
| JC Pubs Ltd | Hospitality | 2020 |
| JD Logistics and Warehousing Services Ltd | Transport & logistics | 2020 |
| JD Springfield Limited | Financial services | 2021 |
| Jefe Holdings Limited | Real estate | 2022 |
| JEN Kirby Limited | Information & communication | 2012 |
| Jerox Limited | Professional & scientific | 2013 |
| Jessvik Ltd | Hospitality | 2025 |
| JET Projects Ltd | Administrative & support | 2023 |
| Jhon Brian Limited | Wholesale & retail | 2026 |
| Jibbsauto Ltd | Wholesale & retail | 2020 |
| Jimmytech Limited | Wholesale & retail | 2025 |
| Jivenmotors Ltd | Wholesale & retail | 2023 |
| JJ Heating and Cooling Ltd | Construction | 2018 |
| JJH Talent Recruitment Limited | Wholesale & retail | 2009 |
| JJP Builder Ltd | Construction | 2025 |
| JJP Homeservices Ltd | Construction | 2017 |
| JK Car Care Limited | Wholesale & retail | 2026 |
| JK Wills Limited | Professional & scientific | 2014 |
| JKL Electrical Ltd | Construction | 2014 |
| JM Chef's Table Ltd | Hospitality | 2022 |
| JM Consultancy Solutions Ltd | Financial services | 2018 |
| JM Evergreens Limited | Wholesale & retail | 2016 |
| JMC Keystone Ltd | Administrative & support | 2025 |
| JMS Logistics Ltd | Transport & logistics | 2025 |
| JN Darres Limited | Real estate | 2021 |
| JNH Data Solutions Ltd | Information & communication | 2025 |
| Jocten Limited | Wholesale & retail | 2025 |
| Johan Infotech Ltd | Administrative & support | 2017 |
| John and Van Services Limited | Transport & logistics | 2020 |
| John Ladbury & Co Limited | Manufacturing | 2006 |
| John Spencer Square Management Company Limited | Households | 1984 |
| Join-It Limited | Administrative & support | 2013 |
| Jointxpert Limited | Health & social care | 2023 |
| Jomo Clothing Ltd | Wholesale & retail | 2025 |
| Jonkco Limited | Professional & scientific | 2014 |
| Jordan Brettell Limited | Real estate | 1994 |
| Journal of Comparative Pathology LLP | | 2014 |
| Journey UP Ltd | Health & social care | 2025 |
| Joyaku Healthcare Limited | Professional & scientific | 2016 |
| Joystone Court Management Company Limited | Households | 1968 |
| JP Linden Limited | Financial services | 2021 |
| JPR Advisory Ltd | Other services | 2025 |
| JPW Assets Limited | Administrative & support | 2024 |
| JR Stunts Ltd | Information & communication | 2023 |
| Jrhw Holdings Ltd | Real estate | 2026 |
| JRM 24 Properties Ltd | Real estate | 2024 |
| JRM Construction Services Limited | Construction | 2015 |
| JS Coffee House Ltd | Financial services | 2021 |
| JSM Logistics Transfer Ltd | Wholesale & retail | 2020 |
| JSN Consulting Limited | Professional & scientific | 2026 |
| JT3 Utilities Limited | Energy | 2020 |
| Julie Clark Health Limited | Health & social care | 2023 |
| Julius Cezar Limited | Wholesale & retail | 2016 |
| Just Charlie Film Limited | Information & communication | 2015 |
| Just in Time Mobile Fleet Wash Limited | Transport & logistics | 2020 |
| Justscore Ltd | Information & communication | 2025 |
| Juul's Sandwich Catering Ltd. | Hospitality | 2014 |
| Juurus Ltd | Transport & logistics | 2023 |
| Juvero Ltd | Wholesale & retail | 2026 |
| Juzer Ltd | Wholesale & retail | 2024 |
| K & D Management Services Ltd | Real estate | 2002 |
| K & R Windows & Doors Limited | Construction | 2008 |
| K and K Solicitors Limited | Professional & scientific | 2017 |
| K H Cars UK Limited | Wholesale & retail | 2007 |
| K&D Rental LLP | | 2022 |
| K&K BCD Limited | Transport & logistics | 2022 |
| K&N More Solutions Ltd | Construction | 2023 |
| K. Eduam Company Limited | Real estate | 2017 |
| K.V.J. Fairdeal Limited | Wholesale & retail | 1967 |
| Kabs Kidz Ltd | Wholesale & retail | 2020 |
| Kadason Consultancy Ltd | Professional & scientific | 2014 |
| Kafe Express Coffee Limited | Wholesale & retail | 2025 |
| Kagyei Limited | Construction | 2019 |
| Kailasanathar Ltd | Wholesale & retail | 2025 |
| Kaizen Certification Ltd | Other services | 2022 |
| KANARYA1907 Ltd | Hospitality | 2024 |