| Jews' Temporary Shelter | Health & social care | 2003 |
| Jigsaw Invest Property Services Limited | Other services | 2016 |
| Jill Samuels Productions Limited | Information & communication | 2003 |
| JKP Solutions Limited | Professional & scientific | 2009 |
| JNG Homes Limited | Real estate | 2020 |
| JNI Limited | Construction | 2016 |
| Joba International London Ltd | Education | 1992 |
| John Jacobs Limited | Administrative & support | 2003 |
| Joket Informatics Ltd | Information & communication | 2014 |
| JP Motion Ltd | Information & communication | 2024 |
| JPR Courts Limited | Construction | 2012 |
| JPS Painting & Decorating Ltd | Construction | 2015 |
| Jrpass Ltd | Administrative & support | 2008 |
| Jsmo Ltd | Health & social care | 2023 |
| Julie Holdings Limited | Construction | 1961 |
| Juloby Group Limited | Professional & scientific | 2023 |
| Justin Reece Property Limited | Construction | 2014 |
| K.W.S (Distribution) Limited | Transport & logistics | 1997 |
| KAS Catering Limited | Hospitality | 2001 |
| Kasa Estates Limited | Real estate | 2023 |
| KCH Associates Ltd | Professional & scientific | 2014 |
| KDS & Associates Limited | Professional & scientific | 1993 |
| Kelross Racing Limited | Arts & recreation | 2002 |
| Kernow Industrial Services Limited | Construction | 2019 |
| Kernow Property Investments Limited | Real estate | 2010 |
| KFL Consultants Ltd. | Arts & recreation | 2018 |
| Kitty Collins Leic Ltd | Hospitality | 2019 |
| KIW Developments Limited | Construction | 2019 |
| Knight & Day Drainage and Plumbing Limited | Other services | 2018 |
| Knight by Design Ltd | Real estate | 2014 |
| Knight James Acquisitions Limited | Real estate | 2019 |
| Know HOW HR Limited | Administrative & support | 2009 |
| Koukan Developments Ltd | Construction | 2019 |
| Krans Consultancy Limited | Administrative & support | 2022 |
| Krish Estates Ltd | Real estate | 2016 |
| Krish Investment London Limited | Real estate | 2026 |
| Kube Homes Limited | Construction | 2007 |
| Kushty UK Limited | Professional & scientific | 2024 |
| Laboratory Perfumes Ltd | Professional & scientific | 2012 |
| Lahara Ltd | Professional & scientific | 2012 |
| Lakes Global Limited | Transport & logistics | 2011 |
| Lama Investments Limited | Financial services | 2020 |
| Lancelot Central Ltd | Professional & scientific | 2020 |
| Lanka Files Ltd | Information & communication | 2019 |
| Lapd London Limited | Real estate | 2013 |
| Laroc Estates Limited | Real estate | 2011 |
| Lashbrook Properties Limited | Construction | 1984 |
| Laxman Limited | Wholesale & retail | 2012 |
| LE Consulting London Limited | Professional & scientific | 2018 |
| Leavesden Construction Company Limited | | 1984 |
| Legge and Braine Limited | Professional & scientific | 2004 |
| Leocrest Limited | Construction | 2014 |
| Leonard Mann & Co. Limited | Administrative & support | 2007 |
| Leoside Limited | Real estate | 2014 |
| LEV EL LEV Properties Limited | Real estate | 2024 |
| Limber Construction Ltd | Construction | 2017 |
| Lionheart Brand Ltd | Manufacturing | 2017 |
| Lisa Eldridge Beauty Ltd | Wholesale & retail | 2019 |
| Lismore Trading Ltd | Hospitality | 2018 |
| Littlewoods Retail Limited | Professional & scientific | 1946 |
| LOGO1013 Limited | Administrative & support | 2018 |
| London Crest Ltd | Wholesale & retail | 2013 |
| Lookout Productions Ltd | Information & communication | 2012 |
| Ltas Capital LLP | | 2009 |
| Lumin Hive Limited | Administrative & support | 2024 |
| Luxe Lofts Ltd | Construction | 2018 |
| Luxurious Italian Furnishings Ltd | Wholesale & retail | 2008 |
| Luxurious Italian Investments Limited | Financial services | 2024 |
| LW Finance Limited | Professional & scientific | 2002 |
| LW Investments Limited | Professional & scientific | 2002 |
| Lyra Investments (UK) Limited | Financial services | 2008 |
| Lyttelton Holdings Limited | Financial services | 2021 |
| LZ Learning Centre Ltd | Education | 2021 |
| M & C Building Services Solutions Ltd | Construction | 2016 |
| M Scaffolding Ltd | Construction | 2015 |
| M.A. Consultancy Services London Ltd | Professional & scientific | 2026 |
| M.J.R. Consultancy Limited | Professional & scientific | 1998 |
| MA Bureau Limited | Professional & scientific | 2016 |
| Maclav Properties Limited | Real estate | 2018 |
| Magex Limited | Health & social care | 2018 |
| Magic Kingdom Properties Ltd | Real estate | 2019 |
| Magnum OIL & GAS Limited | Extraterritorial | 2004 |
| Mail-Tex Limited | Manufacturing | 1985 |
| Manasseh Consulting Ltd | Professional & scientific | 2024 |
| Manta Media Capital Limited | Professional & scientific | 2025 |
| Maple Oak Property Investments Limited | Real estate | 2025 |
| Marcella Mcging Marketing Limited | Professional & scientific | 2012 |
| Market Bridge Holdings Limited | Financial services | 2017 |
| Market Bridge II Limited | Financial services | 2017 |
| Market Bridge Limited | Financial services | 2017 |
| Marlborough Regents Limited | Households | 2010 |
| Maroon Blue Ltd | Information & communication | 2018 |
| MAS Property and Investment Ltd | Construction | 2019 |
| Massi Driveland Ltd | Education | 2024 |
| Mativision Limited | Information & communication | 2012 |
| Maven Design Limited | Professional & scientific | 2008 |
| Maxebit London Limited | Financial services | 2023 |
| Mayland Investments Limited | Real estate | 2021 |
| MAZ. P Co Ltd | Transport & logistics | 2019 |
| Mckinlay Recruitment Services Limited | Administrative & support | 1998 |