| Jigsaw Projects Ltd | Construction | 2019 |
| Jixgate Properties Limited | Other services | 1977 |
| Jmms Properties Limited | Real estate | 2024 |
| John O'Brien Estates Ltd | Hospitality | 2010 |
| JPG Property Consultants Ltd | Real estate | 2026 |
| JPT Plastering Limited | Construction | 2013 |
| Just BO Ltd | Hospitality | 2013 |
| Just Letting London Limited | Real estate | 2013 |
| Justinway Limited | Wholesale & retail | 1983 |
| K O Kickboxers Limited | Arts & recreation | 2022 |
| K West 1 Ltd | Hospitality | 2025 |
| Kanta London Ltd | Wholesale & retail | 2015 |
| Kapa Medicare Limited | Health & social care | 2009 |
| Karma Waters Capital Limited | Real estate | 2019 |
| Key Mergers and Acquisitions Limited | Extraterritorial | 2002 |
| Kickboxing Elite International Ltd | Arts & recreation | 2023 |
| Kickboxing Private Lessons Limited | Arts & recreation | 2023 |
| Kingdom Kreations Limited | Manufacturing | 2021 |
| Kirlam Import-Export Limited | Transport & logistics | 1989 |
| Kokkinos Investments LLP | | 2025 |
| Koulla Sergi Styling Ltd | Other services | 2018 |
| KRM Enterprises Ltd | Real estate | 2011 |
| Kumaresh Reporting Ltd | Health & social care | 2023 |
| KY LAB Solutions Ltd | Professional & scientific | 2024 |
| LA Alpha Ltd | Other services | 2019 |
| Lally Property Holdings Ltd | Real estate | 2019 |
| Landlords Buy Homes (UK) LLP | | 2025 |
| Langham First Ltd | Hospitality | 2019 |
| Langley Fruit & VEG Limited | Wholesale & retail | 2014 |
| Lasersight (Essex) Limited | Health & social care | 1998 |
| Lauren & Alysia Investments (UK) Limited | Administrative & support | 2009 |
| Legion Arts Projects Limited | Arts & recreation | 2018 |
| Legitt Limited | Wholesale & retail | 2016 |
| LEP Estates Limited | Real estate | 2021 |
| LET and Forget Limited | Real estate | 2021 |
| Lewis Dodson Limited | Financial services | 2011 |
| LHK Finchley Road Ltd | Households | 2017 |
| Lilywhite Financial Limited | Financial services | 2016 |
| Lilywhite Property Limited | Real estate | 2018 |
| Logic Plumbing Ltd | Construction | 2022 |
| Lombard Amalgamations Limited | Financial services | 1986 |
| London and City Investments Limited | Real estate | 2019 |
| London Prime Estates LLP | | 2019 |
| London Spine Specialist Ltd | Health & social care | 2014 |
| Longmont Properties Limited | Construction | 2009 |
| Lonsto Investment Limited | Real estate | 1970 |
| Louis Michael Limited | Professional & scientific | 2011 |
| Louise Goodwin Limited | Real estate | 1961 |
| Loula Limited | Professional & scientific | 2012 |
| Loyola Investment Management Limited | Professional & scientific | 2020 |
| LTH Nurseries Limited | Health & social care | 2021 |
| Ludlow Court Management Company Limited | Households | 2004 |
| Lugs (Garages) Limited | Extraterritorial | 2000 |
| Lumiere Property Management Ltd | Real estate | 2018 |
| Luxurious Kickboxing International Ltd | Arts & recreation | 2020 |
| Lyndhurst Properties Limited | Real estate | 1999 |
| M & a Lift Installations Limited | Professional & scientific | 2018 |
| M Adams & Associates Limited | Professional & scientific | 2000 |
| M L Evans Limited | Arts & recreation | 2017 |
| M Pro 101 Limited | Hospitality | 2016 |
| M&O Construction Limited | Construction | 2022 |
| MAC Chingford Ltd | Real estate | 2015 |
| MAC London Homes Ltd | Real estate | 2020 |
| MAG3D Limited | Professional & scientific | 2025 |
| Marj Solutions Limited | Information & communication | 2018 |
| Marku Painting & Decorating Ltd | Construction | 2024 |
| Marquee Magic Event Hire Ltd | Other services | 2018 |
| Marquee Magic Ltd | Other services | 2018 |
| Marselli Aluminium Limited | Wholesale & retail | 2017 |
| Martial Training Ltd | Education | 2015 |
| Martin London Developments Limited | Real estate | 2021 |
| Marylebone W1 Properties Limited | Real estate | 2018 |
| Mauro Chiarello Ltd | Information & communication | 2018 |
| Mchaj Limited | Real estate | 2020 |
| Meadingrow Investments Limited | Real estate | 1977 |
| Meridien Luxe Limited | Real estate | 2025 |
| MHK Estates Management Ltd | Real estate | 2022 |
| MHK London Ltd. | Real estate | 2017 |
| MI Homes Group Ltd | Real estate | 2016 |
| MI Marketing Consultancy Ltd | Professional & scientific | 2016 |
| Miamax Group Limited | Hospitality | 2016 |
| Miamax One Limited | Hospitality | 2016 |
| Miamax Three Limited | Hospitality | 2016 |
| Miamax Two Limited | Hospitality | 2016 |
| Microcom Services Limited | Real estate | 2005 |
| Millennium Estates Services Limited | Real estate | 1996 |
| Miller Car Services Limited | Transport & logistics | 1997 |
| Minotaur Automobiles Limited | Wholesale & retail | 2008 |
| Miri Gardener Limited | Administrative & support | 2024 |
| Miss Anna Fashions Limited | Real estate | 1978 |
| Mistel Limited | Real estate | 2005 |
| Morell Mouldings Resources Limited | Administrative & support | 2002 |
| Moremead Contracts Limited | Real estate | 2011 |
| Mountview Estates PLC | Real estate | 1937 |
| Mrod Consultancy Limited | Real estate | 2015 |
| Msda Property Ltd | Real estate | 2016 |
| Murder My Darlings Limited | Information & communication | 1995 |
| My Home Property Management Ltd | Real estate | 2021 |
| N J K Business Services Ltd | Professional & scientific | 2015 |
| N-T Support's Ltd | Education | 2021 |