| Leuco (Great Britain) Limited | Wholesale & retail | 1981 |
| Libardi's Gelato and Coffee Limited | Hospitality | 2025 |
| Lilac Investments 2 Limited | Financial services | 2024 |
| Lilyblase Limited | Administrative & support | 2025 |
| Lime Grove Developments Limited | Construction | 1983 |
| LJ Mahoney Investments Ltd | Real estate | 2020 |
| LK & SP Holdings Limited | Real estate | 2020 |
| Lkennedy Consultancy Ltd | Education | 2023 |
| LKL Limited | Administrative & support | 2015 |
| London Climate Hire Limited | Construction | 2016 |
| Longstone Whin Limited | Professional & scientific | 2009 |
| Lookers Plastering and Drylining Limited | Construction | 2017 |
| Lovelight Events Ltd | Arts & recreation | 2014 |
| Lovelight Holdings Ltd | Arts & recreation | 2018 |
| LPR Electrical Ltd | Construction | 2024 |
| LS Motor Sales Ltd | Wholesale & retail | 2026 |
| Luella Dixon HR Solutions Ltd | Administrative & support | 2015 |
| Lumex Electrical Ltd | Construction | 2009 |
| Luxdry Limited | Wholesale & retail | 2025 |
| Lydia Cooke Ltd | Professional & scientific | 2019 |
| M & R Interiors Limited | Wholesale & retail | 1997 |
| M LEE Fire Engineering Limited | Construction | 2019 |
| M W Fitness Limited | Health & social care | 2014 |
| Mabel 61 Limited | Professional & scientific | 2022 |
| MAC1 Carpentry & Joinery Limited | Construction | 2007 |
| Maclin Limited | Professional & scientific | 2002 |
| Maclin Pumps Limited | Construction | 1995 |
| Magdrill Group Holdings Limited | Financial services | 2023 |
| Magdrill UK Limited | Wholesale & retail | 1998 |
| MAJ Group Ltd | Real estate | 2024 |
| Mannex Development Limited | Wholesale & retail | 1992 |
| Manorwalk Limited | Extraterritorial | 2005 |
| Mansell & Co Limited Liability Partnership | | 2006 |
| Mantle (Dunmow) Limited | Administrative & support | 1999 |
| Mantle (Dunmow) Project Management Limited | Administrative & support | 1999 |
| Mantle (Hertford) Limited | Real estate | 2011 |
| Mantle (Saffron) Limited | Real estate | 2006 |
| Mantle Estates LLP | | 2007 |
| Mantle Holdings Limited | Real estate | 1995 |
| Mantle Management LLP | | 2010 |
| Marbeck Ltd | Real estate | 2019 |
| Maria's Selection Ltd | Wholesale & retail | 2023 |
| Marie Cuff Design Ltd. | Professional & scientific | 2020 |
| Marisella Solutions Ltd | Other services | 2025 |
| Markets in Financial Instruments Consultancy Ltd. | Professional & scientific | 2006 |
| Martin and Martin Surveyors Ltd | Professional & scientific | 2015 |
| Martinelli Medical Services Ltd | Health & social care | 2020 |
| Masiello Ltd | Information & communication | 2023 |
| MAX Segal Limited | | 1968 |
| MCP Engineering Plastics Limited | Manufacturing | 2000 |
| MEC Investments Limited | Real estate | 1999 |
| Medical Developments UK Limited | Wholesale & retail | 2012 |
| Melvern Management Company Limited | Households | 1993 |
| Melvyn Rutter Limited | Wholesale & retail | 1981 |
| MHB Property Limited | Real estate | 1997 |
| Michael Bradley Consulting Ltd | Information & communication | 2024 |
| Michael Testler & Co. Limited | Professional & scientific | 1993 |
| Michael Testler Property Services Limited | Professional & scientific | 1988 |
| Midsummer Advisory Services Limited | Professional & scientific | 2012 |
| Millars Group Limited | Real estate | 2018 |
| Millars Maltings Limited | Real estate | 1970 |
| Mindbeam Ltd | Education | 2010 |
| Mitrechem Limited | Manufacturing | 2004 |
| MJ Services Limited | Professional & scientific | 2006 |
| MO Spinal Limited | Health & social care | 2014 |
| Mobilityplus Wheelchairs Ltd | Wholesale & retail | 2019 |
| Modistro Limited | Wholesale & retail | 2004 |
| Momo BS Limited | Hospitality | 2024 |
| Moonshot Padel Ltd | Arts & recreation | 2023 |
| Motocaddy Limited | Manufacturing | 2004 |
| Mountfitchet Investment Limited | Real estate | 2020 |
| MPG Communication Ltd | Information & communication | 2011 |
| MR Barbers (Braintree) Limited | Other services | 2015 |
| MR Barbers Franchising Ltd | Other services | 2014 |
| Mulligan Fencing Contracting Limited | Construction | 2009 |
| Mussa & Mary Ltd | Health & social care | 2015 |
| MWA Search Limited | Professional & scientific | 2025 |
| National Schools Snowsports Association | Education | 2016 |
| NDN Media Ltd | Information & communication | 2026 |
| Nestalgia Ltd | Real estate | 2025 |
| Network Techs Limited | Professional & scientific | 2015 |
| Neusepharma Ltd | Professional & scientific | 2017 |
| Nevill Design and Build Ltd | Construction | 2024 |
| New Smile Ltd | Health & social care | 2020 |
| Nexus Supplies Limited | Information & communication | 1996 |
| Nichegrad Limited | Financial services | 2023 |
| Nick Tait Consultancy Services Limited | Professional & scientific | 2026 |
| Nicola's Soft Furnishings Limited | Manufacturing | 2024 |
| Nitronics Limited | Wholesale & retail | 1985 |
| Nkvr Ltd | Hospitality | 2012 |
| NMJ Rivers Consulting Limited | Professional & scientific | 2017 |
| Nockolds Solicitors Limited | Professional & scientific | 2012 |
| Northreach Group Ltd | Real estate | 2020 |
| Nova Business Services Limited | Administrative & support | 2004 |
| Novumtec Ltd | Extraterritorial | 2011 |
| Nrwa Developments Limited | Construction | 2023 |
| Nrwa Ltd | Administrative & support | 2017 |
| Nxrd Limited | Professional & scientific | 2026 |
| OAD Creative Limited | Administrative & support | 2012 |
| Oakridge Property Group Ltd | Real estate | 2023 |