| JDO Studio Ltd | Wholesale & retail | 2025 |
| JDP Accountants Limited | Professional & scientific | 2020 |
| Jean Road Property Limited | Real estate | 2026 |
| Jeas Solutions Ltd | Administrative & support | 2021 |
| Jedi Racing Cars Limited | Manufacturing | 1997 |
| Jeeworks Ltd | Real estate | 2024 |
| JEM Sales & Marketing Limited | Professional & scientific | 1999 |
| JEM Sports and Social LLP | | 2024 |
| JEMI9 Resources Ltd | Professional & scientific | 2026 |
| Jenco Controls and Export Limited | Manufacturing | 1963 |
| Jermenterprises Ltd | Wholesale & retail | 2026 |
| Jeseli Properties Ltd | Real estate | 2025 |
| Jetter J Drainage Services Ltd | Water & waste | 2026 |
| JF & B Investments Limited | Professional & scientific | 2003 |
| JF Keyline Estates Ltd | Real estate | 2025 |
| JG Homes Improvements Ltd | Administrative & support | 2016 |
| JGW &SON Ltd | Other services | 2018 |
| JIB Productions Limited | Information & communication | 2013 |
| Jidsol Ltd | Information & communication | 2012 |
| Jidsol Properties Limited | Real estate | 2021 |
| JIM Murray Whiskey Library Limited | Wholesale & retail | 2023 |
| JIM Murray Whisky Tastings Limited | Professional & scientific | 2008 |
| Jireh Property Management Ltd | Households | 2021 |
| Jispa Logistics Ltd | Transport & logistics | 2024 |
| JJ Groundworks Northampton Ltd | Construction | 2024 |
| JJ Links Limited | Manufacturing | 2006 |
| JJ Management and Consulting Ltd | Professional & scientific | 2013 |
| JJ Property Nivas Ltd | Real estate | 2017 |
| JK Property Developments Group Ltd | Real estate | 2026 |
| JK Speed Ltd | Transport & logistics | 2025 |
| JKD Ravewear Ltd | Wholesale & retail | 2025 |
| JKF Detailing Limited | Wholesale & retail | 2025 |
| JKH Stores Ltd | Wholesale & retail | 2016 |
| JKR Power Investment Ltd | Real estate | 2017 |
| JL Appliances Limited | Other services | 2023 |
| JL EL Jefe Limited | Transport & logistics | 2016 |
| JL Plant Hire Ltd | Wholesale & retail | 2019 |
| JLB Support Services Limited | Information & communication | 2002 |
| JLK Transport Ltd | Transport & logistics | 2021 |
| JLT Scaffolding Ltd | Construction | 2018 |
| JM Painting Decorating & Spraying Limited | Construction | 2025 |
| JM Trade Company Ltd | Construction | 2024 |
| Jmac Engineering Services Ltd | Construction | 2024 |
| JME Electrical Contractors Limited | Construction | 2012 |
| JME Hospitality Limited | Hospitality | 2023 |
| JML Global Solutions Ltd | Information & communication | 2011 |
| JMS Treasury Consultancy Limited | Professional & scientific | 2024 |
| Jobans Ltd | Financial services | 2023 |
| Joga Property Ltd | Real estate | 2025 |
| John Haining Construction Limited | Construction | 2025 |
| John Redden (Farms) Limited | Agriculture & fishing | 1960 |
| John Redden Limited | Wholesale & retail | 1953 |
| Johnbargain Ltd | Wholesale & retail | 2022 |
| Johndua Ltd | Wholesale & retail | 2026 |
| Johnstone Family Butchers Ltd | Wholesale & retail | 2020 |
| Johnstone Handyfix Limited | Administrative & support | 2017 |
| Jokandos Ltd | Wholesale & retail | 2023 |
| Jolanta Waszkiewicz Limited | Wholesale & retail | 2021 |
| JON Boak Ltd | Professional & scientific | 2018 |
| JON Facci Personal Training Limited | Professional & scientific | 2022 |
| Jonei Limited | Wholesale & retail | 2024 |
| Jordan Lyle Limited | Information & communication | 2022 |
| Jordanna Marston Photography Ltd | Arts & recreation | 2015 |
| Jotnar Composites Ltd | Manufacturing | 2026 |
| Joy Holdings Ltd | Financial services | 2025 |
| Joyby Limited | Health & social care | 2025 |
| Joytrans Ltd | Transport & logistics | 2018 |
| JP Mobile Sports Massage Limited | Health & social care | 2014 |
| Jpgl Developments Limited | Real estate | 2016 |
| Jpgs Accounting Services Limited | Professional & scientific | 2025 |
| JPM Remarketing Limited | Professional & scientific | 2025 |
| JPR Performance Limited | Arts & recreation | 2025 |
| JPR Wilcox Limited | Manufacturing | 2023 |
| JPS Autocentre Limited | Wholesale & retail | 2018 |
| JPW Contracting Solutions Ltd | Administrative & support | 2013 |
| JR Building Comp Ltd | Construction | 2025 |
| JR Driving Services Ltd | Transport & logistics | 2026 |
| JR Gutter VAC Limited | Administrative & support | 2015 |
| JR Property Management & Maintenance Ltd | Real estate | 2025 |
| Jrapha Care Limited | Wholesale & retail | 2023 |
| JRG Drivers Limited | Other services | 2016 |
| JS Earthworks Ltd | Construction | 2026 |
| JS Fitness Group Limited | Arts & recreation | 2023 |
| JS Plumbing & Heating Services Limited | Construction | 2025 |
| JS Project Solutions Ltd | Professional & scientific | 2021 |
| JSF Planning Limited | Construction | 2011 |
| JST Forktrucks Limited | Professional & scientific | 2004 |
| JST Storage Solutions Limited | Manufacturing | 2021 |
| JSV Building Solutions Ltd | Construction | 2018 |
| JSV Construction Ltd | Construction | 2021 |
| JT Plumbing and Construction Limited | Construction | 2020 |
| JTK 2025 Limited | Health & social care | 2025 |
| JTY Wood Ltd | Hospitality | 2026 |
| Jubilee Pictures Limited | Information & communication | 2004 |
| Julian Gray Consulting Ltd | Information & communication | 2008 |
| Julies Flower Boutique Ltd | Wholesale & retail | 2025 |
| Jumping Turtles Ltd | Education | 2026 |
| Junikez Limited | Health & social care | 2024 |
| Junior Joshi Driving School Limited | Education | 2019 |
| Junior Joshi Ltd | Real estate | 2024 |