| Jonathan Weedon Ltd | Administrative & support | 2012 |
| Joneeta Tech UK Limited | Information & communication | 2021 |
| Jones and Richards Limited | Real estate | 2000 |
| Jones Group Holdings Limited | Financial services | 2014 |
| Jordan Andrew Mark Industries Ltd. | Wholesale & retail | 2012 |
| Josephine Mullally Ltd | Administrative & support | 2023 |
| Josh Birch Films Ltd | Information & communication | 2024 |
| Josiah-Browne Solutions Limited | Professional & scientific | 2025 |
| Josino Driving School Ltd | Extraterritorial | 2025 |
| Josoz Limited | Information & communication | 2024 |
| Journey Limited | Arts & recreation | 1995 |
| Jowett Change Solutions Ltd | Information & communication | 2015 |
| Joy of Sales Limited | Information & communication | 2015 |
| Joy World Shop Limited | Wholesale & retail | 2023 |
| Joyful Constructions Limited | Construction | 2022 |
| Joyful Dwellings Ltd | Real estate | 2022 |
| Joyful Holding Group Limited | Financial services | 2022 |
| JP Capital Ltd | Real estate | 2018 |
| JP Chohan Ltd | Professional & scientific | 2018 |
| JP DEV Ltd | Information & communication | 2025 |
| JP Mckim Services Limited | Construction | 2018 |
| JP School of Motoring Ltd | Education | 2023 |
| JPC Architects Ltd | Professional & scientific | 2010 |
| JPE Consulting Services Limited | Information & communication | 2015 |
| Jphd Limited | Other services | 2012 |
| JPM Impex Ltd | Wholesale & retail | 2023 |
| JPM Sport Ltd | Arts & recreation | 2003 |
| Jppk Properties Limited | Real estate | 2021 |
| JR Design & Decorate Ltd | Professional & scientific | 2023 |
| JR3 Property Ltd | Real estate | 2015 |
| JR3 South East Ltd | Real estate | 2016 |
| JRK Enterprises Ltd | Wholesale & retail | 2025 |
| JRK Tech Solutions Ltd | Information & communication | 2025 |
| JRM Design Engineering Ltd | Professional & scientific | 2025 |
| JS Arborcraft Ltd | Administrative & support | 2013 |
| JS Commercial Solutions Ltd | Professional & scientific | 2024 |
| JS Psychology Services Ltd | Health & social care | 2020 |
| JS Training Options Limited | Education | 2006 |
| JSA Architects Limited | Professional & scientific | 2007 |
| Jshh Limited | Administrative & support | 2015 |
| Jsrk Limited | Information & communication | 2014 |
| JSS Real Estate Limited | Real estate | 2026 |
| JSV Infotech Limited | Information & communication | 2021 |
| JT Ventures Ltd | Wholesale & retail | 2018 |
| JTS Equity Ltd | Real estate | 2025 |
| Jubal Ltd | Professional & scientific | 2019 |
| Jubilee Community Church (Maidenhead) | Other services | 2010 |
| Judkins Limited | Professional & scientific | 1903 |
| Juggurnauth Ltd | Wholesale & retail | 2020 |
| Julani Properties Ltd | Real estate | 2020 |
| Julian 76 Ltd | Transport & logistics | 2015 |
| Julivanda Limited | Real estate | 1979 |
| Jumpshare Ltd | Wholesale & retail | 2025 |
| Junior&Parents Ltd | Education | 2021 |
| Junix Systems Limited | Information & communication | 2010 |
| Jupiter Property Finance UK Limited | Wholesale & retail | 2007 |
| Just Global UK Ltd | Professional & scientific | 1994 |
| Justice Precious Metals Ltd | Manufacturing | 2022 |
| Justin Law Solicitors Limited | Professional & scientific | 2016 |
| Justintime Super Cleaning Services Ltd | Administrative & support | 2017 |
| Juttla Bros Limited | Real estate | 2023 |
| JV Property Ventures Ltd | Real estate | 2024 |
| JWA Consultancy Limited | Professional & scientific | 2008 |
| K & J Associates Limited | Real estate | 1998 |
| K & L Heating & Bathrooms Limited | Construction | 2007 |
| K F Charles Consulting Ltd | Information & communication | 2025 |
| K Majid Ltd | Information & communication | 2014 |
| K Matthews & Sons Limited | Construction | 2012 |
| K&A Consultancy Solutions Limited | Professional & scientific | 2018 |
| K&H De-Samay Ltd | Real estate | 2021 |
| K.A Builders Ltd | Construction | 2023 |
| K.Gale Gardening Services Limited | Administrative & support | 2025 |
| K.M. Property Development Company Limited | Financial services | 1971 |
| K.T. Brand Management Consultancy Ltd | Professional & scientific | 2018 |
| K.T.I.H. Ltd | Construction | 2023 |
| K2 Consultancy Services Ltd | Information & communication | 2019 |
| Kaarster Developments Limited | Wholesale & retail | 2004 |
| Kabeerah Ltd | Administrative & support | 2019 |
| Kaboodle Creative Ltd | Information & communication | 2002 |
| Kadam Design and Consultancy Limited | Real estate | 2024 |
| Kahlon Transport Ltd | Real estate | 2026 |
| KAI Cleanz Limited | Administrative & support | 2026 |
| KAI Conversations Limited | Administrative & support | 2020 |
| KAI Solutions Limited | Professional & scientific | 2012 |
| Kaig Consulting Limited | Professional & scientific | 2017 |
| Kairos Realty Limited | Real estate | 2024 |
| Kakealiciouss Ltd | Hospitality | 2018 |
| Kaldon Limited | Transport & logistics | 2001 |
| Kalpataru Labs Limited | Professional & scientific | 2011 |
| Kalra Business Services Ltd | Professional & scientific | 2015 |
| Kals N Crew Barbers Limited | Other services | 2021 |
| Kamira Property Ltd | Real estate | 2022 |
| Kamran & Co Accounts Services Ltd | Professional & scientific | 2024 |
| Kandy Kingdom Ltd | Wholesale & retail | 2022 |
| Kanghua UK Limited | Wholesale & retail | 2019 |
| Kanini Limited | Information & communication | 2025 |
| Kanso Facilities Management Limited | Administrative & support | 2018 |
| Kantara Group Holding 1 Limited | Real estate | 2023 |
| Kantara Group Limited | Real estate | 2021 |
| Kantara Retail Limited | Wholesale & retail | 2020 |