| JF Financial Limited | Professional & scientific | 2016 |
| JFH Advisory Limited | Health & social care | 2024 |
| JFS Interim Solutions Ltd | Professional & scientific | 2011 |
| JG Estate Management Limited | Real estate | 2013 |
| JG Tapia Ltd | Information & communication | 2017 |
| JGE Medical Ltd | Health & social care | 2016 |
| JH M&E Engineering Ltd | Professional & scientific | 2026 |
| JH Site Management Ltd | Professional & scientific | 2015 |
| Jihco Ltd | Real estate | 2025 |
| Jijik Ventures Limited | Hospitality | 2021 |
| Jill Parker Consulting Limited | Professional & scientific | 2015 |
| JJ & GM Henderson Practice Limited | Health & social care | 2018 |
| JJ Furniture Trading Ltd | Wholesale & retail | 2025 |
| JJ Selected Store Limited | Wholesale & retail | 2024 |
| JK Orthopaedics Limited | Health & social care | 2019 |
| JKQ Thornton Limited | Health & social care | 2013 |
| JL Brands Limited | Wholesale & retail | 2020 |
| JL Setters Ltd | Administrative & support | 2026 |
| Jlinnco UK Ltd | Professional & scientific | 2017 |
| JLM Supplies Ltd | Health & social care | 2018 |
| JM Assets & Property UK Limited | Real estate | 2026 |
| JM Creations Ltd | Information & communication | 2024 |
| JM Healthcare Services UK Limited | Health & social care | 2022 |
| JM Hospitality Ltd | Hospitality | 2019 |
| JM Urology Limited | Health & social care | 2021 |
| JMH Cars Limited | Wholesale & retail | 2003 |
| JMS Hospitality Ltd | Hospitality | 2018 |
| JN Security Systems Ltd | Professional & scientific | 2015 |
| JNM ENT Ltd | Health & social care | 2022 |
| JNM Recruitment Ltd | Professional & scientific | 2026 |
| Joadal Ltd | Hospitality | 2018 |
| Jobot Holdings Limited | Professional & scientific | 2019 |
| Jocelyn Limited | Health & social care | 2019 |
| John Berry Digital Limited | Information & communication | 2026 |
| John Elder Limited | Extraterritorial | 2004 |
| John Jenkin Jones Engineering Services Limited | Construction | 2023 |
| John Rocke ENT Limited | Health & social care | 2024 |
| Johnston Anaesthesia Limited | Health & social care | 2017 |
| Joined UP Health Limited | Wholesale & retail | 2018 |
| Joint Investment Solutions Limited | Real estate | 2017 |
| Joint Orthopaedics Ltd | Health & social care | 2019 |
| Jokaro Limited | Construction | 1990 |
| Jolo Holdings Limited | Financial services | 2024 |
| JON Castle Consulting Limited | Health & social care | 2012 |
| Jordan Sheppard Inc Limited | Administrative & support | 2024 |
| Jordan Sheppard Limited | Administrative & support | 2006 |
| Jorge Limited | Manufacturing | 2017 |
| Josama Holdings Limited | Financial services | 2020 |
| Josama Limited | Wholesale & retail | 2010 |
| Joseph James Furniture Outlet LLP | | 2019 |
| Jove Actuarial Limited | Professional & scientific | 2018 |
| Jozomo Ltd | Real estate | 2025 |
| JP Project 50 Ltd | Professional & scientific | 2019 |
| JPA Watch Company Ltd | Wholesale & retail | 2015 |
| JPK Property Partners Ltd | Real estate | 2025 |
| JRA Solutions Limited | Information & communication | 2015 |
| JRL Orthopaedics Ltd | Health & social care | 2018 |
| JRW Commercial Management Limited | Professional & scientific | 2020 |
| JSB Media Limited | Information & communication | 2024 |
| JSB Techhive UK Limited | Information & communication | 2025 |
| JSC Medical Ltd | Health & social care | 2018 |
| Jsds Properties Limited | Real estate | 2022 |
| JSH Aesthetics Ltd | Health & social care | 2026 |
| JSH Publications Ltd | Information & communication | 2025 |
| Jskdigital Limited | Professional & scientific | 2023 |
| JTL Medchem Consulting Limited | Professional & scientific | 2025 |
| JTS (Godwin) Limited | Construction | 2025 |
| JTS (Minshall) Limited | Construction | 2025 |
| JTS Construction (UK) Ltd | Construction | 2018 |
| JTS Developments Ltd | Construction | 2016 |
| Judah Systems Ltd | Administrative & support | 2022 |
| Jude Relief Worldwide | Health & social care | 2023 |
| Julian Kronfli Limited | Information & communication | 2014 |
| Jump Seat Productions Limited | Information & communication | 2017 |
| Junior Saloon Car Championship Limited | Construction | 2014 |
| Junior Touring Car Championship Limited | Construction | 2013 |
| Juniper Property Projects Ltd | Real estate | 2025 |
| Juno Skin Ltd | Wholesale & retail | 2018 |
| Jurga D Studio Ltd | Health & social care | 2024 |
| Just GMC Limited | Health & social care | 2016 |
| Just Indemnify IT Ltd | Administrative & support | 2024 |
| Just SAS Limited | Manufacturing | 2013 |
| Justdoctor Limited | Professional & scientific | 2023 |
| JV Minns Ltd | Professional & scientific | 2015 |
| JW Elite Football Coaching Ltd | Arts & recreation | 2025 |
| JW Property Enterprise Ltd | Real estate | 2025 |
| JW7 Holdings Ltd | Financial services | 2025 |
| Jwgl Limited | Health & social care | 2024 |
| Jwtt LLP | | 2026 |
| JYS Services UK Ltd | Construction | 2019 |
| K & L Property Developments Ltd | Real estate | 2025 |
| K Clinic Limited | Health & social care | 2023 |
| K E Graham Ltd | Health & social care | 2014 |
| K M Qureshi Limited | Health & social care | 2022 |
| K R Couplings Limited | Extraterritorial | 2004 |
| K&C Real Estate Solutions Ltd | Households | 2024 |
| K&L Property Renovations Ltd | Real estate | 2025 |
| K. Barnes Limited | Health & social care | 2003 |
| K. Hinduja Ltd | Health & social care | 2010 |
| K2 Performance & Development Limited | Construction | 2025 |