| Jace Electrical Ltd | Construction | 2019 |
| Jack Parker Plastering Limited | Construction | 2026 |
| Jack Willis Flying Ltd | Administrative & support | 2017 |
| Jackie Rose Limited | Arts & recreation | 2011 |
| Jackthakedesign Ltd | Arts & recreation | 2022 |
| Jaezra Services Ltd | Administrative & support | 2025 |
| JAH Installations Ltd | Construction | 2019 |
| Jals Holdings Limited | Financial services | 2023 |
| Jane Edwards Consultancy Limited | Professional & scientific | 2016 |
| Jarballs Ltd | Manufacturing | 2008 |
| Jason Paul Trading Ltd | Wholesale & retail | 2020 |
| JB Aluminium Systems Ltd | Construction | 2018 |
| JBL Prop Ltd | Real estate | 2021 |
| Jbox Engineering Consultancy Limited | Professional & scientific | 2019 |
| JC Group of Companies Limited | Administrative & support | 2018 |
| JDM Financial Services Ltd | Professional & scientific | 2024 |
| Jdms Install & Services Ltd | Administrative & support | 2018 |
| Jdtf Homes Ltd | Real estate | 2022 |
| Jdtf Property Ltd | Real estate | 2022 |
| JE Housing Ltd | Real estate | 2026 |
| Jebo Properties Ltd | Real estate | 2022 |
| Jedas Holdings Ltd | Real estate | 2021 |
| Jele CM8 Ltd | Hospitality | 2026 |
| Jelley BEE Honey Ltd | Hospitality | 2023 |
| Jennings Engineering (UK) Ltd | Wholesale & retail | 2011 |
| Jetense Consultants Limited | Professional & scientific | 2024 |
| Jettco Plastering Limited | Construction | 2013 |
| JFM Truck Care Ltd | Wholesale & retail | 2022 |
| JH Fabrications (Witham) Ltd | Manufacturing | 2025 |
| JK Flooring Limited | Other services | 2005 |
| JKE Trading Ltd | Construction | 2024 |
| JM Freelancer Limited | Professional & scientific | 2025 |
| JM Sports Trading Consultancy Limited | Professional & scientific | 2023 |
| JMD Boiler Solutions Ltd | Construction | 2019 |
| JNS Business Limited | Wholesale & retail | 2026 |
| John Chater | Professional & scientific | 1957 |
| John P Chick Limited | Information & communication | 2020 |
| John Sutcliffe (Medical Consulting) Limited | Health & social care | 2017 |
| Johnson (1996) Limited | Wholesale & retail | 1934 |
| Johnson&Sons Construction Ltd | Construction | 2025 |
| Joint Heirs Ventures Limited | Wholesale & retail | 2016 |
| Joly Consulting Ltd | Professional & scientific | 2020 |
| JPP Recruitment Ltd | Administrative & support | 2019 |
| JQ Prop Limited | Real estate | 2018 |
| JS Creative & Design Ltd | Information & communication | 2025 |
| JS Lewis Antiques Limited | Wholesale & retail | 2019 |
| JS Property Maintenance Ltd | Construction | 2018 |
| JSK Utilities Limited | Energy | 2017 |
| Jumble B Limited | Wholesale & retail | 2014 |
| Jump Start Centre Limited | Health & social care | 2013 |
| Juniper’S Plants Ltd | Wholesale & retail | 2024 |
| Just Recruitment Group Ltd | Administrative & support | 1990 |
| Just Recruitment Trustee Limited | Administrative & support | 2017 |
| Justin Rata Osteopath Limited | Health & social care | 2003 |
| JWA Construction Services Ltd. | Administrative & support | 2017 |
| JWA Pipework Solutions Limited | Construction | 2013 |
| K K S J Catering Ltd | Hospitality | 2019 |
| K-Coles & Turner Property Ltd | Real estate | 2023 |
| K.A.A.P. International Limited | Manufacturing | 1993 |
| K.M Exterior Renovations Ltd | Construction | 2026 |
| Kaima Limited | Health & social care | 2020 |
| Kaisa Investments Ltd | Professional & scientific | 2015 |
| Kallista Aesthetics Ltd | Health & social care | 2015 |
| Kamhas Limited | Real estate | 2020 |
| Kampa Investments Limited | Administrative & support | 2014 |
| Karma Quartz Limited | Wholesale & retail | 2017 |
| Karma Surfaces Ltd | Wholesale & retail | 2019 |
| Kashem ALI Talukder Ltd | Hospitality | 2025 |
| Kashteq Limited | Professional & scientific | 2025 |
| Kassim Enterprise Ltd | Wholesale & retail | 2012 |
| Kavod Ltd. | Financial services | 2014 |
| KB Buildings Limited | Construction | 1998 |
| Kblue Limited | Transport & logistics | 2023 |
| KCT Direct Ltd | Wholesale & retail | 2026 |
| Kear & SON Total Utilities Limited | Construction | 2000 |
| Keeble and Barrett Ltd | Construction | 2024 |
| Kelvedon & Feering Rugby Union Football Club Ltd | Education | 2021 |
| Kemosynthesis Limited | Health & social care | 2016 |
| Kempco Limited | Manufacturing | 1985 |
| Kempton Smith Limited | Professional & scientific | 2015 |
| Kenley Limited | Professional & scientific | 2020 |
| Kent Internet Services Limited | Professional & scientific | 1995 |
| Keston Homes Limited | Real estate | 2019 |
| Keystride Consulting Limited | Information & communication | 2010 |
| KGR Group Holdings Ltd | Financial services | 2026 |
| Kgreat Services Limited | Other services | 2025 |
| Kiddocrafters Ltd | Information & communication | 2025 |
| Kilmanock Accounting Ltd | Professional & scientific | 2015 |
| Kilmarnock Internet Services Limited | Professional & scientific | 1995 |
| Kilnlake Properties Limited | Construction | 2001 |
| Kimber Holdings Ltd | Financial services | 2022 |
| Kimia Distribution Limited | Extraterritorial | 2020 |
| Kimia International Limited | Extraterritorial | 1992 |
| Kimia Trading Limited | Extraterritorial | 2020 |
| Kimiauk Limited | Extraterritorial | 2020 |
| Kind Hearts Preschool Limited | Education | 2014 |
| Kinetix Academy CIC | Health & social care | 2022 |
| Kingstar Limited | Administrative & support | 1998 |
| Kingz Landscapes Ltd | Other services | 2021 |
| Kingz Property Development Ltd | Real estate | 2022 |