| Legacy Heating Ltd | Construction | 2025 |
| Legology Limited | Wholesale & retail | 2010 |
| Leisure Licence Ltd | Administrative & support | 2010 |
| Lema Property Ltd | Real estate | 2018 |
| Lemon Plaice Limited | Hospitality | 2011 |
| Lemon Sherbert Technology Limited | Information & communication | 2011 |
| Lets Play Rock Ltd | Education | 2009 |
| Letzgo Ltd | Wholesale & retail | 2024 |
| Leyton Cross Holdings Limited | Administrative & support | 2017 |
| LG Productions Artists Ltd | Hospitality | 2022 |
| LGM Cleaning Services Ltd | Administrative & support | 2023 |
| LHL Holdings Limited | Real estate | 2024 |
| Lifemax Direct UK Limited | Wholesale & retail | 2005 |
| Lifemax Limited | Wholesale & retail | 2003 |
| Limm Communications Limited | Professional & scientific | 2007 |
| Lindencomms Limited | Information & communication | 2009 |
| Linelocal Limited | | 1986 |
| Linetex Limited | Information & communication | 1988 |
| Linetex Sales & Installations Limited | Information & communication | 1991 |
| Linextex Computers Ltd | Information & communication | 2001 |
| Link Hamson Limited | Wholesale & retail | 1991 |
| Linknumber Ltd | Information & communication | 2023 |
| Lismore Properties Limited | Real estate | 2013 |
| Litten Tree Antiques Ltd | Wholesale & retail | 2018 |
| Little FOX Holdings Limited | Professional & scientific | 2007 |
| Little KS Travel Limited | Administrative & support | 2025 |
| Little ME Canada Water Ltd | Health & social care | 2017 |
| Little ME Day Nurseries Limited | Financial services | 2012 |
| Little ME East India Docks Ltd | Health & social care | 2019 |
| Little ME Skyline Plaza Limited | Health & social care | 2011 |
| Little ME Thatcham Limited | Health & social care | 2015 |
| Little Talkers Limited | Health & social care | 2012 |
| Little Tinker Limited | Professional & scientific | 1993 |
| Little YUM Factory Limited | Hospitality | 2016 |
| Littles PUB Co Ltd | Hospitality | 2025 |
| Lm-Surveys & Inspections Ltd | Professional & scientific | 2025 |
| Loading Zone Ltd | Arts & recreation | 2019 |
| Logoyo Ltd | Wholesale & retail | 2021 |
| Lollypop Lane Limited | Wholesale & retail | 2024 |
| London Stainless Fasteners Ltd | Wholesale & retail | 1983 |
| Lonely Giant Studios Limited | Information & communication | 2019 |
| Lorencia London Limited | Other services | 2026 |
| Lovegrove Engineering & Maintenance Ltd | Professional & scientific | 2022 |
| Lower Drove Lane East Residents Association Ltd | Households | 2000 |
| LP SD One Hundred Seven Limited | Wholesale & retail | 2023 |
| LPD Homes Ltd | Real estate | 2026 |
| LPL Projects Limited | Construction | 2021 |
| Lrequestran Ltd | Agriculture & fishing | 2025 |
| LSN Media Limited | Information & communication | 1986 |
| Lucentum Capital Ltd | Wholesale & retail | 2025 |
| Lucian Distribution Ltd | Transport & logistics | 2019 |
| Luke Rogers CP Ltd | Administrative & support | 2025 |
| Lusentuk Ltd | Professional & scientific | 2026 |
| LVW Coaching Ltd | Health & social care | 2023 |
| Lyall Consulting Limited | Professional & scientific | 2017 |
| Lycart Ltd | Health & social care | 2020 |
| Lyons & Wood Limited | Hospitality | 2023 |
| Lyvoo Ltd | Financial services | 2021 |
| M & J Wilson Limited | Construction | 2014 |
| M a Smith Groundwork & Brickwork Limited | Construction | 2012 |
| M L B Plumbing and Heating Limited | Construction | 2007 |
| M Y Auto Services Ltd | Wholesale & retail | 2013 |
| M&D Heating & Ventilation Limited | Construction | 2008 |
| M. & G. Rubber Stamps Limited | Manufacturing | 1999 |
| M.C.S Property Solutions Limited | Construction | 2022 |
| M4 Commercials Limited | Wholesale & retail | 2022 |
| M4 Recruitment Limited | Administrative & support | 2015 |
| M4 Specialist Limited | Administrative & support | 2021 |
| M4 Talent Group Limited | Administrative & support | 2026 |
| Maak London Limited | Wholesale & retail | 2019 |
| MAC Plastering Ltd | Construction | 2010 |
| MAE ME London Limited | Administrative & support | 2021 |
| Maestro Management Ltd | Administrative & support | 2023 |
| Maizin Ltd | Information & communication | 2024 |
| Makan Malaysia UK LLP | | 2020 |
| Malcolm Franks Limited | Professional & scientific | 2015 |
| Malkin Pest Control Ltd | Agriculture & fishing | 2023 |
| Malou Limited | Information & communication | 2012 |
| Managementors Holding Company Limited | Financial services | 2026 |
| Manakamana Trade Ltd | Wholesale & retail | 2024 |
| MANDARIN11 Ltd | Hospitality | 2025 |
| Manoir Antiques & Decorative Interiors Limited | Wholesale & retail | 2022 |
| Marchdown Holdings Limited | Construction | 2020 |
| Marchdown Leyton Cross LLP | | 2018 |
| Marchdown Securities Limited | Construction | 2013 |
| Maria Glaud Healthcare Ltd | Health & social care | 2019 |
| Mark Oglesby Limited | Information & communication | 2011 |
| Markwa Care Personnel Limited | Health & social care | 2018 |
| Marlston Farmgirl LLP | | 2021 |
| Marlston Water Company Limited | Water & waste | 2024 |
| Marsell Network Ltd | Transport & logistics | 2017 |
| Maserfan Consulting Limited | Information & communication | 2015 |
| Maspace Ltd | Construction | 2020 |
| Masterbuild Trading Ltd | Wholesale & retail | 2026 |
| Matrix IT Consultancy Ltd | Information & communication | 2007 |
| Matterdam Limited | Professional & scientific | 2018 |
| Matthes Ltd | Real estate | 2018 |
| MAX Rutherford Media Limited | Information & communication | 2009 |
| Maxim Aviation Ltd | Transport & logistics | 2008 |
| Maxim Pensions Limited | Financial services | 2014 |