| JOE Charles Holdings Limited | Real estate | 2022 |
| JOE Charles Homes Limited | Construction | 2018 |
| John Autos Ltd | Wholesale & retail | 2025 |
| John North Hall (High Wycombe) Management Company Limited | Households | 2009 |
| John P Limited | Professional & scientific | 2008 |
| Johnston Farina Ltd | Professional & scientific | 2024 |
| JOL Golf Shop Limited | Wholesale & retail | 2019 |
| Jolan Services Limited | Administrative & support | 2020 |
| Jonathan Burgin Limited | Construction | 2009 |
| Jones & Co Procurement Services Limited | Professional & scientific | 2017 |
| Jonny G Productions Limited | Extraterritorial | 2021 |
| Jopen Properties Limited | Real estate | 1992 |
| Joseph Arnold & Sons Limited | Mining & quarrying | 1993 |
| Joynson and Gordon Ltd. | Manufacturing | 2004 |
| JP Greek Limited | Hospitality | 2024 |
| JPF (UK) Ltd. | Wholesale & retail | 2014 |
| Jpriley Limited | Professional & scientific | 2023 |
| JS King Ltd | Real estate | 2021 |
| JS Safety Ltd. | Wholesale & retail | 2006 |
| JS Stag Ltd | Arts & recreation | 2016 |
| JSC Event Consulting Ltd | Other services | 2019 |
| JST Connective Consultancy Ltd | Professional & scientific | 2010 |
| JST Engineering & Contracting Ltd | Professional & scientific | 2024 |
| JTE Integration Ltd | Administrative & support | 2021 |
| JTO Protection Limited | Financial services | 2026 |
| Jtprservices Ltd | Professional & scientific | 2024 |
| Jules Consultancy Ltd | Professional & scientific | 2015 |
| Julia Whitehead 21 Limited | Information & communication | 2004 |
| Jumpthrow Ltd | Information & communication | 2025 |
| Jungo Active Ltd | Information & communication | 2019 |
| Jungo Productions Ltd | Information & communication | 2022 |
| Jurassic Classics Ltd | Administrative & support | 2020 |
| Just Promo Lanyards Limited | Wholesale & retail | 2018 |
| JWI Property Ltd | Real estate | 2025 |
| JYM Media Ltd | Professional & scientific | 2025 |
| K R Plasterers Limited | Construction | 2016 |
| K&K Winchester Sushi Limited | Hospitality | 2025 |
| K8 Consultancy Limited | Administrative & support | 2017 |
| Kadanzichim Ltd | Health & social care | 2022 |
| Kallenhard Engineering Ltd | Wholesale & retail | 2016 |
| Kalybeai Software and Artificial Intelligence Technology Ltd | Information & communication | 2024 |
| Kaneo Celebrations Ltd | Wholesale & retail | 2021 |
| Kane’S Modern Classics Limited | Wholesale & retail | 2026 |
| Kanicli Limited | Arts & recreation | 2013 |
| Kara Monte Limited | Information & communication | 2013 |
| Karen Archer Limited | Health & social care | 2011 |
| Karimi Real Estates Ltd | Real estate | 2021 |
| Karisi Limited | Agriculture & fishing | 2022 |
| Karls Consolidated Engineers Ltd | Information & communication | 2014 |
| Karuga Limited | Information & communication | 2008 |
| Kasim Enterprises Limited | Hospitality | 2024 |
| Kate Rees Coaching Limited | Professional & scientific | 2017 |
| Kathy Coleman Limited | Professional & scientific | 2012 |
| Kavanaghs (ST Albans) Management Company Limited | Households | 2004 |
| Kawzl Ltd | Professional & scientific | 2023 |
| Kayleigh Brennan Ltd | Information & communication | 2019 |
| Kayman Developments Limited | Real estate | 2019 |
| KBJ Property Company Ltd | Real estate | 2022 |
| KC Buildify Limited | Construction | 2025 |
| KC Planthire Ltd | Construction | 2019 |
| KC Pro Cleaning Ltd | Administrative & support | 2023 |
| KC Sports Marketing Ltd | Wholesale & retail | 2021 |
| KC5 Marketing Ltd | Professional & scientific | 2024 |
| KDK Archaeology Ltd | Professional & scientific | 2012 |
| Kebab YEE Limited | Hospitality | 2025 |
| Kedtacc Advisory Limited | Professional & scientific | 2022 |
| Keegrowth Ltd | Professional & scientific | 2025 |
| Keep IT Green Outdoor Services Ltd | Administrative & support | 2025 |
| Keikai Ltd | Information & communication | 2023 |
| Keith Corless Associates Limited | Information & communication | 1983 |
| Kelly Hinds Consulting Ltd | Real estate | 2019 |
| Kemp Construction Creative Design & Build Ltd | Manufacturing | 2025 |
| Kennedy Electrical Limited | Construction | 2026 |
| Kestrel Energy Limited | Hospitality | 2002 |
| Kestrel Project Services Ltd | Professional & scientific | 2018 |
| Kevin Henry Limited | Extraterritorial | 2006 |
| Kevin Holt (Interim Logistics Management) Limited | Transport & logistics | 2006 |
| Kevin Paul Humphrey Limited | Education | 2014 |
| Kevlar Business Consultants Limited | Administrative & support | 2022 |
| Key Partnership Recruitment Ltd | Administrative & support | 2020 |
| Keybeats Ltd | Education | 2017 |
| Keychange Coaching Limited | Professional & scientific | 2020 |
| Keysafe Tenant Vetting Limited | Administrative & support | 2022 |
| Keystone Professional Management Services Limited | Professional & scientific | 2017 |
| KG Arjis UK Ltd | Information & communication | 2018 |
| Khalsa Dashmesh Limited | Construction | 2025 |
| Khawaja Energy Solution Ltd | Energy | 2026 |
| Khaya Care Ltd | Health & social care | 2023 |
| KHM Enterprises Ltd | Wholesale & retail | 2011 |
| KHT IT Services Limited | Information & communication | 2023 |
| KI Motors Ltd | Wholesale & retail | 2019 |
| Kichaka Tales Ltd | Professional & scientific | 2024 |
| Kidz Zone Club Ltd | Health & social care | 2016 |
| Kierstone Project Management Ltd | Professional & scientific | 2020 |
| Kiing of Neons Ltd | Wholesale & retail | 2021 |
| KIM and Kerry's Canines LP | | 2023 |
| Kind Clean LLP | | 2025 |
| Kingdom K9 Ltd | Wholesale & retail | 2025 |
| Kingfisher Court (Loudwater) Management Company Limited | Households | 2003 |
| Kingfisher House RTM Company Limited | Households | 2018 |