| JSL Hydraulic Hoses Ltd | Professional & scientific | 2023 |
| JSR Consulting Limited | Information & communication | 2025 |
| JT Clark Construction Limited | Construction | 2023 |
| JT Clark Group Limited | Construction | 2025 |
| JT Clark Maintenance Limited | Construction | 2025 |
| Jtattamtreesurgeons Ltd | Administrative & support | 2025 |
| JTL Projects Ltd | Construction | 2025 |
| JTS Project Control Ltd | Administrative & support | 2025 |
| Jubilee Grange Management Company Limited | Households | 2003 |
| Jude Lung Health Ltd | Health & social care | 2025 |
| Jukebox Media Ltd | Professional & scientific | 2018 |
| Julian Christian (Garden Buildings) Ltd | Manufacturing | 2020 |
| Julian Christian Trading Limited | Manufacturing | 2009 |
| Julian Whitfield Ltd | Construction | 2008 |
| Jump Topco Limited | Financial services | 2017 |
| Jumping Jacks Childcare Limited | Education | 2004 |
| Junior's Transport Ltd | Transport & logistics | 2017 |
| Juniorruntingz Ltd | Health & social care | 2023 |
| Junshu Safety Ltd | Professional & scientific | 2026 |
| Jusons Glebe Limited | Real estate | 2009 |
| Just Aerials Ltd | Construction | 2016 |
| Just Baguettes Limited | Wholesale & retail | 2011 |
| Just Cutz Ltd | Other services | 2022 |
| Just Rachel Ltd | Hospitality | 2017 |
| Just Secure IT Ltd | Administrative & support | 2025 |
| Just Spuds Ltd | Hospitality | 2025 |
| Just Torque Limited | Extraterritorial | 2024 |
| Justbmoore Limited | Education | 2014 |
| Justin and Co Accountants Limited | Professional & scientific | 2014 |
| JVS Export (UK) Limited | Administrative & support | 2002 |
| JW Auto Refresh Ltd | Administrative & support | 2025 |
| JW Construction Services Limited | Professional & scientific | 2022 |
| Jwek LLP | | 2017 |
| Jymsushi Limited | Hospitality | 2021 |
| K & a Scaffolding Ltd | Construction | 2013 |
| K & W Consultancy Limited | Information & communication | 2012 |
| K & Z Fencing Landscaping and Sheds Ltd | Administrative & support | 2022 |
| K Building Limited | Construction | 2021 |
| K C L Cleaning Services Limited | Administrative & support | 2007 |
| K D Carwash Limited | Administrative & support | 2014 |
| K Fletcher Building Services Ltd | Construction | 2026 |
| K J Barnett Limited | Construction | 2005 |
| K M Commercials (Aylesbury) Ltd | Extraterritorial | 2014 |
| K M Mardell Limited | Professional & scientific | 2014 |
| K N Facey Limited | Construction | 2018 |
| K Redding Consultancy Limited | Information & communication | 2025 |
| K White Property Services Limited | Households | 2011 |
| K&A Scaffolding NO 1 Ltd | Construction | 2022 |
| K&K Cleaning Ltd | Administrative & support | 2012 |
| K&Q Wendover Ltd | Hospitality | 2021 |
| K-Pot! Ltd | Wholesale & retail | 2025 |
| K.A.E Construction Ltd | Construction | 2018 |
| K.Panikkar Limited | Health & social care | 2010 |
| K.R.L International Holding Ltd | Education | 2020 |
| K.W. Harrison & Sons Limited | Construction | 2003 |
| K2 Dynamics Limited | Wholesale & retail | 2015 |
| K2 Events & Catering Ltd | Hospitality | 2025 |
| Kaab Group Ltd | Transport & logistics | 2021 |
| Kaak Limited | Wholesale & retail | 2020 |
| Kabelan Limited | Wholesale & retail | 2014 |
| Kabir & SON Ltd | Health & social care | 2023 |
| Kabir Associates Ltd | Other services | 2015 |
| Kabrus Locks Ltd | Wholesale & retail | 2018 |
| Kabul Dera Ltd | Hospitality | 2024 |
| Kadapsy Limited | Transport & logistics | 2017 |
| Kadence Talent Ltd | Administrative & support | 2023 |
| Kadence Training Ltd | Information & communication | 2012 |
| Kadikoy Limited | Hospitality | 2016 |
| Kahban Caasi Ltd | Construction | 2017 |
| Kaill Consultancy & Training Ltd | Education | 2015 |
| Kaill Management Services Ltd | Administrative & support | 2011 |
| Kaldep Limited | Health & social care | 2015 |
| Kalmekolen Limited | Professional & scientific | 2025 |
| Kaluma Limited | Professional & scientific | 2008 |
| Kalvin Selmer Contemporaneous Limited | Manufacturing | 2020 |
| Kamo Aylesbury Ltd | Other services | 2026 |
| KAMSONNO9 Ltd | Hospitality | 2025 |
| KAN Realty Partners Ltd | Real estate | 2026 |
| Kanalima Consulting Ltd | Administrative & support | 2024 |
| Kandathil Group Ltd | Health & social care | 2026 |
| Kandeez Dance Ltd | Education | 2023 |
| Kanimo Services Limited | Administrative & support | 2024 |
| Kanyii Ltd | Wholesale & retail | 2026 |
| Kapil Limited | Wholesale & retail | 2021 |
| Kapm Consultants Ltd | Hospitality | 2014 |
| Karamuliar Ltd | Hospitality | 2025 |
| Karmil Ltd | Construction | 2023 |
| Karos Media Limited | Arts & recreation | 2025 |
| Karoshi Technology Ltd | Information & communication | 1999 |
| Kartik Ltd | Wholesale & retail | 2005 |
| Karvin Limited | Information & communication | 2026 |
| Karzilla Ltd | Wholesale & retail | 2026 |
| Kasama Wear Limited | Wholesale & retail | 2026 |
| Kashmir Gardens Ltd | Hospitality | 2025 |
| Kasim Jewellers Ltd | Wholesale & retail | 2024 |
| Kaskee Ltd | Health & social care | 2022 |
| Kaskee Real Estate Ltd | Real estate | 2024 |
| Kass Solutions Limited | Other services | 2024 |
| Kassia Limited | Wholesale & retail | 2011 |
| Kates Companions Ltd | Other services | 2016 |