| JCA Cars Ltd | Administrative & support | 2014 |
| JCM Sparks Limited | Construction | 2025 |
| JCR Auto Techx Limited | Manufacturing | 2026 |
| JD Construction & Interiors Ltd | Construction | 2015 |
| JD Global Advantage Limited | Professional & scientific | 2012 |
| JD LI Properties (UK) Limited | Real estate | 2025 |
| JD Scooter Company Ltd | Wholesale & retail | 2025 |
| Jdbl Real Estate Ltd | Real estate | 2020 |
| JDC Property Holding Ltd | Real estate | 2020 |
| JDR Solutions Ltd | Construction | 2022 |
| JDS Striving for Excellence CIC | Education | 2020 |
| Jdtei Limited | Health & social care | 2011 |
| JDW New Horizons Limited | Education | 2020 |
| JE Soft Limited | Information & communication | 2020 |
| Jeffscott Properties Limited | Households | 2023 |
| JEG Drylining Limited | Construction | 2019 |
| Jennis and More Ltd | Wholesale & retail | 2021 |
| Jennystore Ltd | Wholesale & retail | 2025 |
| Jerkpit Caribbean Restaurant Ltd | Hospitality | 2014 |
| Jermolina Art Ltd | Professional & scientific | 2021 |
| Jerry Shawarma Limited | Hospitality | 2023 |
| Jerrydan Ltd | Other services | 2018 |
| Jetspeed Corporate Fuel UK Ltd | Wholesale & retail | 2025 |
| Jett & Jihnar Holding Ltd | Real estate | 2023 |
| Jexora Ltd | Wholesale & retail | 2026 |
| Jeyharlem Limited | Other services | 2025 |
| JF Lakey Limited | Information & communication | 2022 |
| JF Properties Investment Ltd | Real estate | 2025 |
| JF Square Limited | Wholesale & retail | 2024 |
| JFC Barking Limited | Hospitality | 2019 |
| JGB Short Investments Limited | Real estate | 2018 |
| JHA Renovations Ltd | Construction | 2024 |
| Jill Development Consultancy Limited | Professional & scientific | 2017 |
| Jimmy Building Maintenance Ltd | Construction | 2020 |
| Jimmy's Furniture & Appliances Limited | Wholesale & retail | 2020 |
| Jimmyhirecar Limited | Administrative & support | 2021 |
| JJS Corp Ltd | Real estate | 2026 |
| JK ELA Ltd | Real estate | 2024 |
| JK Mureithi Consultancy Limited | Professional & scientific | 2011 |
| JK Network Solutions Ltd | Information & communication | 2012 |
| JK Security Services Limited | Administrative & support | 2025 |
| JKA Commercial Ltd | Professional & scientific | 2026 |
| JKR Accountancy Ltd | Professional & scientific | 2007 |
| Jmac Logistics Ltd | Transport & logistics | 2025 |
| JMB Food Ltd | Hospitality | 2026 |
| JML Cleaners Limited | Administrative & support | 2021 |
| JMT Star Agency Ltd | Administrative & support | 2024 |
| JMT Transport Consultants Limited | Transport & logistics | 2019 |
| JN Associates Limited | Administrative & support | 2022 |
| JNA Motors Ltd | Wholesale & retail | 2026 |
| JNM Residentials Ltd | Real estate | 2025 |
| Joao Bernardo Tavares Inde Ltd | Wholesale & retail | 2025 |
| Joby Venture Properties Ltd | Real estate | 2025 |
| Jock Stewart and Sons Limited | Professional & scientific | 1961 |
| Joda Homes Ltd | Real estate | 2020 |
| JOE Catering (Safari Food) Ltd | Hospitality | 2016 |
| JOE Yankson and Son's Company Limited | Water & waste | 2017 |
| Joegreg Services Limited | Professional & scientific | 2013 |
| Joelez UK Limited | Health & social care | 2023 |
| JOG Energy Limited | Other services | 2024 |
| Johnny Paintings Ltd | Construction | 2026 |
| Johnson & Elizabeth Consultant & Training CIC | Education | 2025 |
| Johnstesho Limited | Construction | 2015 |
| Johny Trans Ltd | Extraterritorial | 2016 |
| Joiv Limited | Information & communication | 2017 |
| Jolly 3D Crystal Ltd | Manufacturing | 2021 |
| Jomel Limited | Public administration | 2024 |
| Jomisluxuryride Ltd | Transport & logistics | 2023 |
| Jomisse Service Ltd | Other services | 2018 |
| Josan Brothers Design and Build Ltd | Construction | 2021 |
| Joshika Ltd | Hospitality | 2026 |
| Josmars Development Limited | Real estate | 2024 |
| Josmars Investments Limited | Real estate | 2019 |
| Josmars Properties Limited | Construction | 2019 |
| Journeyman Consulting Limited | Information & communication | 2023 |
| Jove Decor UK Ltd | Other services | 2025 |
| Jovic Healthcare Ltd | Health & social care | 2026 |
| Jovik Ltd | Wholesale & retail | 2006 |
| Joy Care Agency Ltd | Health & social care | 2004 |
| Joyfull Cleaning Ltd | Administrative & support | 2025 |
| Joy’S Tiny Tots Ltd | Health & social care | 2020 |
| JP Coaching & Consulting Ltd | Health & social care | 2025 |
| JP Sparks Ltd | Construction | 2022 |
| JP Titan Logistics Ltd | Transport & logistics | 2025 |
| JPB Construction Co. Ltd | Construction | 2020 |
| Jppr Ltd | Information & communication | 2026 |
| JR Linen Services Ltd | Other services | 2023 |
| JR Shopfronts Limited | Manufacturing | 2021 |
| JS Hunt Ltd | Administrative & support | 2018 |
| JS London Ltd | Wholesale & retail | 2025 |
| JS UK International Limited | Wholesale & retail | 2019 |
| JSB Corporation Limited | Wholesale & retail | 2025 |
| Jsdm Ltd | Information & communication | 2025 |
| JSS London Ltd | Manufacturing | 2022 |
| JSS UK Properties Limited | Real estate | 2022 |
| JT (Coast to Coast) Ltd | Transport & logistics | 2022 |
| JT Provider Limited | Construction | 2015 |
| JT Specialist Ltd | Construction | 2025 |
| Jt&Z Construction Company Ltd | Construction | 2024 |
| JT-FINANCE7 Ltd | Professional & scientific | 2022 |