| James Hind Statistics Limited | Information & communication | 2022 |
| James Holdings Limited | Professional & scientific | 1990 |
| James House Management Company Limited | Hospitality | 1985 |
| James Jacobs Enterprises Ltd | Transport & logistics | 2026 |
| James Karumbo Care Limited Limited | Health & social care | 2023 |
| James KAY Limited | Real estate | 2019 |
| James Logan's Electrical Services Ltd | Construction | 2019 |
| James Martin Limited | Wholesale & retail | 2016 |
| James Mellors Limited | Arts & recreation | 1977 |
| James Miller Wills Limited | Professional & scientific | 2026 |
| James Moulds Mortgage Adviser Ltd | Financial services | 2022 |
| James Orme Decorators Limited | Construction | 2005 |
| James P Spencer Limited | Construction | 2004 |
| James Property Services Ltd | Real estate | 2020 |
| James R D Anderson Limited | Financial services | 2011 |
| James Real Estate Limited | Construction | 2025 |
| James Rock Consultancy Limited | Information & communication | 2013 |
| James Rogers IT Limited | Real estate | 2009 |
| James Rose Bespoke Ltd | Construction | 2020 |
| James Senior Landscapes Limited | Administrative & support | 2013 |
| James Shannon Property Ltd | Real estate | 2020 |
| James Stuart Properties Limited | Real estate | 2025 |
| James Taylor Properties LLP | | 2020 |
| James Veness Limited | Education | 2012 |
| James Vernon Painting & Decorating Limited | Construction | 2010 |
| James White Hair Limited | Other services | 2022 |
| James Wibberley (Barrister) Limited | Professional & scientific | 2024 |
| Jamesco Holdings Limited | Financial services | 2024 |
| Jameson Lomax Limited | Information & communication | 2001 |
| Jamia Al-Hudaa | Education | 2024 |
| Jamie Jarvis Ltd | Arts & recreation | 2017 |
| Jamie Selby Limited | Education | 2020 |
| Jamie Slack Flooring Ltd | Construction | 2023 |
| Jamie Ward Builders Ltd | Construction | 2017 |
| Jamieson Rentals Ltd | Real estate | 2024 |
| Jamison P Limited | Financial services | 2015 |
| Jamlis Web Ltd | Information & communication | 2024 |
| Jamluk Limited | Other services | 2010 |
| JAMROCK2 Ltd | Professional & scientific | 2024 |
| Jams Multi Industry Solutions Ltd | Transport & logistics | 2018 |
| Jamsa Ltd | Wholesale & retail | 2026 |
| Janara Home Care Services PVT Ltd | Health & social care | 2025 |
| Jandjabatey Medics Ltd | Health & social care | 2021 |
| Jando Property Services Limited | Professional & scientific | 2023 |
| Jane Haskell Mortgage Broker Limited | Financial services | 2023 |
| Jane Madley Limited | Financial services | 2013 |
| Jane Mcclane Pharmaceuticals Ltd | Manufacturing | 2025 |
| Janet Jones Limited | Other services | 2014 |
| Jangor Embedded Solutions Limited | Professional & scientific | 2025 |
| Janice Barfoot Cake and Sugarcraft Ltd | Wholesale & retail | 2019 |
| Janis Janovskis Enterprises Ltd | Information & communication | 2013 |
| Janjua Foods Derby Ltd | Hospitality | 2025 |
| Janjua Ltd | Wholesale & retail | 2024 |
| JANKIRAM00 Ltd | Hospitality | 2025 |
| Jannat Cart Ltd | Wholesale & retail | 2026 |
| Jannco Limited | Information & communication | 2019 |
| Janneh Ltd | Transport & logistics | 2019 |
| Janoream Group Ltd | Financial services | 2022 |
| Janory Properties Limited | Real estate | 1993 |
| Jans Service Centre Limited | Wholesale & retail | 2009 |
| Janson Bridging (UK) Limited | Construction | 1990 |
| Janson Professional Services Limited | Hospitality | 2022 |
| Jansons Leisure & Fishery Ltd | Agriculture & fishing | 2016 |
| Jantaculum Ltd | Information & communication | 2017 |
| Janus TRR Limited | Manufacturing | 2020 |
| Janus-Cpd Limited | Education | 2023 |
| Jaoc Limited | Households | 2024 |
| JAP2023 Ltd | Health & social care | 2023 |
| Japra Property Ltd | Real estate | 2025 |
| Jaques Associates Limited | Administrative & support | 2003 |
| JAR and SON Real Estate Investments Ltd | Real estate | 2020 |
| Jarbell Property Limited | Real estate | 2024 |
| Jarcle LLP | | 2025 |
| Jardine Healthcare Limited | Wholesale & retail | 2016 |
| Jarlath Sayer Motor Racing Ltd | Arts & recreation | 2023 |
| Jarlett & Jones Ltd | Households | 2024 |
| Jaroti Property Services Ltd | Real estate | 2016 |
| Jarowland Ltd | Construction | 2019 |
| Jarream Limited | Wholesale & retail | 2016 |
| Jarrett Group Ltd | Wholesale & retail | 2020 |
| Jarvis Enterprise Transport (JET) Ltd | Transport & logistics | 2008 |
| JAS AMB Ltd | Administrative & support | 2025 |
| JAS Automobile Ltd | Wholesale & retail | 2025 |
| JAS Paye Ltd | Administrative & support | 2025 |
| JAS Payroll Ltd | Administrative & support | 2025 |
| JAS UAP Ltd | Administrative & support | 2025 |
| Jasig Apartments Ltd | Hospitality | 2024 |
| Jasmine Home Care Ltd | Health & social care | 2023 |
| Jasmine Property and Investments Limited | Professional & scientific | 2010 |
| Jasnita Mandhar Ltd | Health & social care | 2015 |
| Jason Cars Limited | Wholesale & retail | 2025 |
| Jason Holmes Windows Limited | Administrative & support | 2007 |
| Jason Holroyd Design Limited | Administrative & support | 2012 |
| Jason Redfearn Limited | Financial services | 2015 |
| Jason Tomlinson Services Limited | Professional & scientific | 2011 |
| Jaspal News & OFF Licence Ltd | Wholesale & retail | 2002 |
| Jaspers Cafe Ltd | Hospitality | 2021 |
| JASRAJ87 Ltd | Real estate | 2025 |
| Jasron Limited | Real estate | 2018 |
| Jassmart Ltd | Wholesale & retail | 2022 |