| JKW Limited | Administrative & support | 2015 |
| JL Obstetrics Limited | Health & social care | 2023 |
| JM Bespoke Complex Care Ltd | Health & social care | 2026 |
| JM DIY & Household Private Ltd | Wholesale & retail | 2024 |
| JM Landscape & Construction Ltd | Administrative & support | 2021 |
| JMI Salons Limited | Other services | 2011 |
| Jmill Property Limited | Real estate | 2025 |
| Jndc Limited | Other services | 2008 |
| Joana's Veterinary Services Ltd | Professional & scientific | 2025 |
| Joanne Awty Ltd | Information & communication | 2018 |
| Joao Logistics Ltd | Transport & logistics | 2017 |
| Joel Bartell Ltd | Arts & recreation | 2022 |
| John Benakis Limited | Information & communication | 2019 |
| John Blake Media Ltd | Information & communication | 2019 |
| John Curtin Limited | Wholesale & retail | 1987 |
| John Dalton Construction Limited | Construction | 2019 |
| John Samonas & Sons Limited | Transport & logistics | 1966 |
| John Williams Close Freehold Limited | Real estate | 2009 |
| Johnjoemcfadden Limited | Administrative & support | 2015 |
| Johnson Friel Building Limited | Construction | 2004 |
| Johnsons Property Group Ltd | Real estate | 2021 |
| Johrik Limited | Information & communication | 2015 |
| Jolly Jumps Ltd | Hospitality | 2024 |
| Joltify Ltd | Construction | 2020 |
| Jomc Property Consultants Limited | Professional & scientific | 2011 |
| JON Group Ltd | Financial services | 2021 |
| Jones Bower Limited | Financial services | 2012 |
| Jonesa Limited | Real estate | 2021 |
| Jongerius (International) Ltd | Manufacturing | 2004 |
| Jongerius Limited | Manufacturing | 2020 |
| Jord Systems Limited | Administrative & support | 2016 |
| Joshila Sharma Consultancy Ltd | Financial services | 2024 |
| Joslyn Hill Communications Ltd | Professional & scientific | 2010 |
| Joss Matthews Ltd | Professional & scientific | 2021 |
| Joubson Resourcing Ltd | Information & communication | 2025 |
| Jourdan Riane Limited | Professional & scientific | 2019 |
| Joy TD Ltd | Professional & scientific | 2025 |
| Joyce Brothers Property Holdings Limited | Real estate | 2018 |
| Joyce ONG Limited | Information & communication | 2005 |
| Joyeux Bordel Ltd | Arts & recreation | 2023 |
| JPL Catering Limited | Hospitality | 2012 |
| JPM Plastering Ltd | Construction | 2018 |
| Jpsm Engineering Ltd | Professional & scientific | 2021 |
| JS Consulting Engineers Ltd | Information & communication | 2013 |
| JS International Trade UK Ltd | Wholesale & retail | 2026 |
| JSR Technology Ltd | Information & communication | 2024 |
| JTC Ventures Limited | Real estate | 1988 |
| Jtms Health Limited | Health & social care | 2013 |
| Judge Management Consultancy Limited | Professional & scientific | 2019 |
| Junelike Limited | Construction | 1978 |
| Jupon Limited | Manufacturing | 1994 |
| Just ADD Music Ltd | Hospitality | 2019 |
| Just for a Woman Limited | Health & social care | 2014 |
| Just Healthcare Limited | Administrative & support | 2005 |
| Just Locums Limited | Administrative & support | 2005 |
| Just Medical Limited | Administrative & support | 2009 |
| Just Riane Limited | Administrative & support | 2022 |
| Just Right Properties Ltd | Real estate | 2024 |
| Justcgray Design Limited | Professional & scientific | 2012 |
| Justpaymobile Ltd | Information & communication | 2018 |
| JW Construction & Civil Engineering Ltd | Construction | 2019 |
| JW Prestige Consulting Ltd | Professional & scientific | 2024 |
| JW2 Assets Ltd | Real estate | 2017 |
| JWC Food Ltd | Wholesale & retail | 2024 |
| JZ Builders Limited | Construction | 2017 |
| K K Investment Ltd | Construction | 2004 |
| K Meadow Pre-School Ltd | Education | 2025 |
| K Paramesh Ltd | Health & social care | 2010 |
| K Squared Engineering Ltd | Construction | 2025 |
| K&Ap Properties Limited | Real estate | 2014 |
| K&H BS Ltd | Construction | 2014 |
| K&P Motors (PVT) Ltd | Wholesale & retail | 2020 |
| K&S Courier Services Ltd | Administrative & support | 2016 |
| K&S Holdings Ltd | Manufacturing | 2020 |
| K&T Investments Limited | Real estate | 2021 |
| K3M Property Investments Ltd | Real estate | 2025 |
| K75 Limited | Construction | 2013 |
| Kabooly Ltd | Information & communication | 2024 |
| Kacp Limited | Financial services | 2014 |
| Kai's Thai Food Ltd | Hospitality | 2010 |
| Kainet Wave Ltd | Information & communication | 2026 |
| Kair Sorbus Limited | Professional & scientific | 2017 |
| Kajan Pubs Holding Limited | Hospitality | 2025 |
| Kajcom Sports Group Limited | Arts & recreation | 2025 |
| Kaker Limited | Financial services | 2014 |
| Kamalakkannan Limited | Wholesale & retail | 2025 |
| Kames Care Ltd | Administrative & support | 2025 |
| Kamis Barberss Ltd | Other services | 2026 |
| Kamis Hairdressers Ltd | Other services | 2026 |
| Kangaroo Maths Trust | Education | 2026 |
| Kangarooz Limited | Manufacturing | 2012 |
| KAP Management Consulting Limited | Professional & scientific | 2017 |
| Karala Creative London Ltd | Professional & scientific | 2021 |
| Karma Vida Ltd | Information & communication | 2020 |
| Karyn Georges Ltd | Professional & scientific | 2026 |
| Kasaju Limited | Information & communication | 2018 |
| Kate Howe Studios Ltd | Arts & recreation | 2020 |
| Kate Lane Limited | Other services | 2020 |
| Kate Morgan Consulting Limited | Information & communication | 2024 |
| Katie Holmes-Smith Ltd | Other services | 2015 |