| JOE & Co Properties Limited | Real estate | 2020 |
| JOE Brindley Guiding Ltd. | Arts & recreation | 2025 |
| Joel Skingle Photography Limited | Professional & scientific | 2013 |
| JOH Taxation Limited | Professional & scientific | 2003 |
| John Douglas Holdings Ltd | Real estate | 2020 |
| John Hatton Investments Limited | Real estate | 1993 |
| John Maher Consulting Ltd | Professional & scientific | 2022 |
| John Mccarthy Aerobatics Ltd | Arts & recreation | 2024 |
| John Smith Vehicle & Asset Repossessions Limited | Administrative & support | 2017 |
| John Wimbleton Consulting Limited | Professional & scientific | 2014 |
| John Wray Country Stoves Limited | Wholesale & retail | 2005 |
| Johnny MAC Ltd | Arts & recreation | 2010 |
| Johnny Van Haeften Limited | Wholesale & retail | 1977 |
| Johnsonclark Ltd | Professional & scientific | 2019 |
| Johnsons Group Limited | Financial services | 2024 |
| Jolly REX Ltd | Information & communication | 2017 |
| Jolter Limited | Professional & scientific | 2017 |
| Jonathan Cass Limited | Professional & scientific | 2019 |
| Jonathan Stewart Photography Limited | Professional & scientific | 2021 |
| Joolbo Ltd | Financial services | 2025 |
| JOR TM Services Ltd | Construction | 2019 |
| Joramalora Ltd | Real estate | 2022 |
| Jordan Kelly Upholstery Ltd | Manufacturing | 2021 |
| Joshi and Hunt Partners Limited | Professional & scientific | 2017 |
| Joshua & Family Limited | Information & communication | 2018 |
| Journalista Ltd | Administrative & support | 2009 |
| Journey Invest Limited | Financial services | 2020 |
| Joyplay Ltd | Administrative & support | 2005 |
| JPG 1 Kings Square Limited | Real estate | 2026 |
| JS & SJ Lynas Ltd | Agriculture & fishing | 2021 |
| JSH Portobello Ltd | Real estate | 2024 |
| JSI Newsagents Ltd | Administrative & support | 2025 |
| JSI PO Limited | Transport & logistics | 2025 |
| Jsra Consulting Ltd | Professional & scientific | 2023 |
| JUB Holland UK Limited | Wholesale & retail | 2019 |
| Juice Marketing Communications Limited | Professional & scientific | 2010 |
| Julia Carrick Luxury Consultancy Limited | Real estate | 2013 |
| Julia Winter Studio Ltd | Professional & scientific | 2026 |
| Julian Brook Ltd | Administrative & support | 2024 |
| Julian Civiero Ltd | Information & communication | 2020 |
| Juliana Gomeso Consultancy Ltd | Information & communication | 2022 |
| JUNCTION9 Ltd | Wholesale & retail | 2009 |
| June Turner Limited | Real estate | 2026 |
| Junior GEO Limited | Wholesale & retail | 2004 |
| Just Design Limited | Administrative & support | 2018 |
| Just the JOB Environmental Enterprise Ltd. | Administrative & support | 2005 |
| Just Wheels Darlington Ltd | Wholesale & retail | 2022 |
| Just Wheels Performance Styling Ltd | Wholesale & retail | 2024 |
| Just Wheels Transport Limited | Transport & logistics | 2025 |
| Justin Rose Consultancy Limited | Arts & recreation | 2022 |
| Justin Rose Enterprises Limited | Arts & recreation | 2022 |
| JV Racing Ltd | Arts & recreation | 2017 |
| JWT Pilgrimages Limited | Administrative & support | 2021 |
| K & B Assets Ltd | Real estate | 2024 |
| K & M Management Ltd | Administrative & support | 2020 |
| K & M Walker T/A Concept Engineer LLP | | 2025 |
| K B19 Ltd | Other services | 2019 |
| K Cross 61 Limited | Real estate | 2023 |
| K Cross Development Ltd | Construction | 2020 |
| K Piercy Plumbing & Sanitary Ltd | Construction | 2011 |
| K S Developments (Hull) Limited | Real estate | 2015 |
| K S Drycleaning Limited | Other services | 2009 |
| K Singh Suppliers Ltd | Wholesale & retail | 2025 |
| K Wallwork Limited | Professional & scientific | 2018 |
| K Z International Yacht Charter Limited | Other services | 1994 |
| K.B. Reinforcements (Western) Limited | Construction | 1974 |
| K5 Tennis Coaching Ltd | Education | 2019 |
| K9 Paws & RAW Ltd | Other services | 2022 |
| KAB Securities Limited | Households | 2022 |
| Kadel Consulting Limited | Information & communication | 2013 |
| Kafkas Patisserie UK Ltd | Manufacturing | 2025 |
| Kahe Studio Ltd | Wholesale & retail | 2025 |
| Kaizarin Limited | Wholesale & retail | 2016 |
| Kala Blends Limited | Wholesale & retail | 2025 |
| Kanav Gold Limited | Wholesale & retail | 2021 |
| Kanawa Ltd | Information & communication | 2019 |
| Kando Studio Ltd | Professional & scientific | 2021 |
| Kanine Dog Walking Limited | Other services | 2023 |
| Kankoo Limited | Professional & scientific | 1997 |
| Kapeti Ltd | Wholesale & retail | 2019 |
| Kappa Lambda Squared Limited | Information & communication | 1993 |
| Kapucin Ltd | Hospitality | 2015 |
| Karine Henderson Consulting Limited | Professional & scientific | 2025 |
| Karis Investment Group Ltd. | Financial services | 2016 |
| Karl Newman Contracts Limited | Construction | 2015 |
| Karoo Software Ltd | Information & communication | 2025 |
| Karro Intelligence Ltd | Wholesale & retail | 2025 |
| Karuna Ltd | Wholesale & retail | 2025 |
| Kasa Communications Limited | Professional & scientific | 2018 |
| Kaso-Mat Ltd | Construction | 2012 |
| Katea Consulting Ltd | Professional & scientific | 2021 |
| Kattec Ltd | Administrative & support | 2015 |
| Kavanagh Consulting Limited | Information & communication | 2025 |
| Kawai-Calderhead Consulting Ltd | Professional & scientific | 2018 |
| KC Property Investments Ltd | Real estate | 2015 |
| KCA Architecture Ltd | Professional & scientific | 2020 |
| Kdesol Limited | Wholesale & retail | 2025 |
| Kefi Textiles Ltd | Manufacturing | 2022 |
| Keith Jones Project Management Limited | Professional & scientific | 2007 |
| Kelfield Consulting Ltd | Professional & scientific | 2021 |