| Jmww Properties Limited | Real estate | 2013 |
| JN Jena Ltd | Wholesale & retail | 2025 |
| JN Karumbos Ltd | Transport & logistics | 2024 |
| JNG Jena Ltd | Wholesale & retail | 2025 |
| JNK Consultancy Ltd | Professional & scientific | 2025 |
| Jnorbs Creative Limited | Arts & recreation | 2024 |
| JO & VIV Company Limited | Real estate | 2022 |
| JO Bare Healthcare Limited | Health & social care | 2014 |
| JO Burnett Ltd | Education | 2013 |
| Jo's Pilates Limited | Arts & recreation | 2014 |
| Joan Transclinig Ltd | Transport & logistics | 2025 |
| Jocap Property Limited | Real estate | 2022 |
| Jodeem GLOBAL2 Limited | Real estate | 2023 |
| Jody Panico Ltd | Other services | 2026 |
| JOE Bygraves Music Ltd | Information & communication | 2020 |
| Joel & Brothers Ltd | Construction | 2020 |
| Joel & MIA Maintenance Services Ltd | Administrative & support | 2006 |
| Joest Services Ltd | Other services | 2017 |
| Joey Football Ltd | Education | 2022 |
| Jogtrack Consulting Limited | Professional & scientific | 2024 |
| John Cleary Mortgages Ltd | Financial services | 2019 |
| John Cook Goldsmith Limited | Wholesale & retail | 2003 |
| John Double Services Ltd | Information & communication | 2015 |
| John Hitchin Cars Limited | Real estate | 2003 |
| John James Commercial Ltd | Real estate | 2018 |
| John Lennon Arts Limited | Extraterritorial | 2009 |
| John Mitchell (Mental Health) Limited | Health & social care | 2017 |
| John Robinson Partnership Limited | Professional & scientific | 2018 |
| John Sheard Farms (Holdings) Limited | Financial services | 2018 |
| John Sheard(Farms)Limited | Agriculture & fishing | 1962 |
| John Sterling Carpentry Limited | Construction | 2008 |
| John Wall Services Limited | Administrative & support | 2012 |
| John Woolfe Racing Limited | Wholesale & retail | 1975 |
| Johnsons Education Limited | Administrative & support | 2016 |
| Jojo Delights Ltd | Wholesale & retail | 2023 |
| Jojo Ellen's School of Healing Ltd | Health & social care | 2023 |
| JOM JOM Enterprise Ltd | Transport & logistics | 2024 |
| Jomesh Ltd | Health & social care | 2022 |
| JON Matson-Higgins Minister & Celebrant Ltd | Other services | 2020 |
| JON SOL Group Limited | Financial services | 2022 |
| JON SOL Investments Limited | Real estate | 2022 |
| Jones and Jones Property Ltd | Real estate | 2024 |
| Jonnotha Super Store Ltd | Hospitality | 2016 |
| Jonny Woolf Ltd | Arts & recreation | 2021 |
| Jonry Auto Repair Limited | Wholesale & retail | 2023 |
| Jootle Technology Ltd | Information & communication | 2017 |
| Jopres Care Ltd | Health & social care | 2019 |
| Joram Jewellers Ltd | Manufacturing | 2025 |
| Jorkel Ltd | Information & communication | 2018 |
| JOS Cafe Ltd | Hospitality | 2018 |
| Josan Investments Ltd | Real estate | 2017 |
| Jose.Pt Ltd | Hospitality | 2019 |
| Joseph Cullinane Limited | Real estate | 2019 |
| Josh Olive Property Ltd | Real estate | 2024 |
| Josias Pharmaceutical Ltd | Wholesale & retail | 2022 |
| Jovicda Ltd | Health & social care | 2023 |
| Joy Collective Online Ltd | Professional & scientific | 2026 |
| Joyce Walker Limited | Information & communication | 2001 |
| Joye Close (Blunham) Limited | Households | 2019 |
| Joyes Chicken Ltd | Hospitality | 2018 |
| Joyful Words Bookshop Limited | Wholesale & retail | 2011 |
| Joyleen Limited | Health & social care | 2024 |
| Joylene Healthcare Ltd | Health & social care | 2019 |
| Jozaal Care Limited | Health & social care | 2018 |
| Jozash Care Limited | Health & social care | 2022 |
| JP & JB Coaching Services Ltd | Education | 2026 |
| JP Care Services Ltd | Real estate | 1996 |
| JP Motor Trade Limited | Wholesale & retail | 2014 |
| JP Parker Consulting Ltd | Professional & scientific | 2023 |
| Jpar Construction Ltd | Construction | 2024 |
| JPD Landscaping Ltd | Administrative & support | 2020 |
| Jpftrade Ltd | Wholesale & retail | 2024 |
| JPH Demolition Limited | Construction | 2021 |
| Jpmg Electrical Contractors Ltd | Manufacturing | 2015 |
| JPN Development Ltd | Construction | 2025 |
| JPN Real Estate Ltd | Real estate | 2025 |
| Jpodproperty Limited | Real estate | 2024 |
| JPT Property Investments Ltd | Real estate | 2019 |
| JR Builders Limited | Construction | 2015 |
| JR Flooring & Building Services Ltd | Construction | 2020 |
| JR Interiors Limited | Construction | 2009 |
| JR Residential Ltd | Real estate | 2023 |
| JR Roofing Contracts Limited | Construction | 2014 |
| JR Sports Management Ltd | Arts & recreation | 2024 |
| JRB Building Solutions Ltd | Construction | 2010 |
| JRC Groundworks Ltd | Construction | 2014 |
| JRC Mechanical Services Limited | Construction | 2025 |
| JRJ Construct and Build Ltd | Construction | 2018 |
| JRJ Properties Ltd | Real estate | 2024 |
| JRS (Welwyn) Property Maintenance Limited | Administrative & support | 2020 |
| Jrvm Limited | Transport & logistics | 2025 |
| JSD Fashion Ltd | Wholesale & retail | 2022 |
| JSI Direct Ltd | Wholesale & retail | 2023 |
| JSK Clutch & Tyre Centre Ltd | Wholesale & retail | 2012 |
| Jskg Ltd | Real estate | 2022 |
| JSP Aluminium Limited | Manufacturing | 1992 |
| JSS United Ltd | Construction | 2023 |
| Jtalk Limited | Information & communication | 2003 |
| JTM Social Work Consultancy Limited | Health & social care | 2017 |
| JTS Contracting Limited | Construction | 2003 |