| Louise Lavery Limited | Information & communication | 2014 |
| Louise Squire Textile Conservation Limited | Professional & scientific | 2011 |
| Lovenergy Limited | Extraterritorial | 2012 |
| Lowlu Ltd | Health & social care | 2024 |
| Lspr Communications Limited | Professional & scientific | 2010 |
| LTB Advisory Ltd | Professional & scientific | 2025 |
| LU Virtual Ltd | Professional & scientific | 2020 |
| Lucidate Limited | Information & communication | 2021 |
| Ludmer Limited | Professional & scientific | 2024 |
| Luke Hart Ltd | Education | 2024 |
| Lund Gaballa Property Ltd | Professional & scientific | 2025 |
| LV Italian Restaurant Ltd | Hospitality | 2024 |
| Lynside Media Limited | Information & communication | 2011 |
| M & a Sports (Tennis) Ltd | Wholesale & retail | 2025 |
| M and N Private Limited | Wholesale & retail | 2026 |
| M K Wardrobes Ltd | Wholesale & retail | 2023 |
| M Second Home Ltd | Health & social care | 2022 |
| M Space Architects Limited | Professional & scientific | 2007 |
| M Space Group Limited | Financial services | 2007 |
| M-Ska Digital Ltd | Information & communication | 2011 |
| M.A. Autos (Ruskin Park) Limited | Real estate | 1959 |
| M.E.B. Facilities Limited | Construction | 1997 |
| M.R. Marine Services Limited | Other services | 2013 |
| M.Space Ltd | Construction | 2002 |
| M9D Limited | Construction | 2023 |
| Maas Martial Arts Ltd | Arts & recreation | 2010 |
| Mabelis Global Enterprise Ltd | Professional & scientific | 2024 |
| Macmillan Consulting Services Limited | Information & communication | 2015 |
| Madeleine Wildey Consulting Limited | Professional & scientific | 2022 |
| Maestro Projects Development Limited | Professional & scientific | 2020 |
| Magnify Research Limited | Professional & scientific | 2019 |
| Magnolia Exterior Ltd | Construction | 2026 |
| Magnolia Landscapes Ltd | Administrative & support | 2022 |
| Magnum Construction Ltd | Construction | 2012 |
| Mailpack International Limited | | 1985 |
| Mainstart Property Management Limited | Households | 1988 |
| Major Plants Limited | Administrative & support | 2009 |
| MAM (UK) Limited | Wholesale & retail | 1989 |
| Mana Property Solutions Ltd | Construction | 2017 |
| Mandy Pitcher Ltd | Other services | 2026 |
| Mangata Limited | Information & communication | 2019 |
| Mango World UK Ltd | Hospitality | 2020 |
| Manila Custom Clothing Ltd | Wholesale & retail | 2022 |
| Mann Renovations Ltd | Construction | 2021 |
| Mansonldn Limited | Information & communication | 2024 |
| Mansouri Applied Geoscience and Engineering Consultancy Ltd | Administrative & support | 2017 |
| Maple Burton Consulting LLP | | 2009 |
| Maple Burton Limited | Administrative & support | 2012 |
| Maple Leaf Consultants Limited | Professional & scientific | 2013 |
| Maples Consulting Limited | Professional & scientific | 2012 |
| Marcomartely.Uk Ltd | Wholesale & retail | 2023 |
| Margaret Henriksson PR Limited | Professional & scientific | 2019 |
| Mark Mannering Barton Ltd | Information & communication | 2025 |
| Market Street Freehold Company Limited | Real estate | 2025 |
| Marketing 360 Limited | Professional & scientific | 2013 |
| Marlo Global Ltd | Professional & scientific | 2018 |
| Marlow House (Teddington) Residents Association Limited | Households | 1966 |
| Marmalade Consultants Limited | Professional & scientific | 2015 |
| Marsh & Parsons (Holdings) Limited | Financial services | 2011 |
| Marsh & Parsons Limited | Real estate | 2005 |
| MAS TV Limited | Manufacturing | 2016 |
| Master Basement Ltd | Construction | 2020 |
| Matco Consulting Limited | Professional & scientific | 2013 |
| Math Lion Ltd | Financial services | 2025 |
| Maths of Twickenham LLP | | 2024 |
| Mathstreetuition Ltd | Education | 2023 |
| Matt Lewis Media Ltd | Professional & scientific | 2024 |
| Mattgill Enterprise Ltd | Wholesale & retail | 2023 |
| Matthew Allchurch Architects Limited | Professional & scientific | 1999 |
| Maxigrowth Limited | Wholesale & retail | 2019 |
| Maxwell Maths LLP | | 2025 |
| Maycock Dental Laboratory Limited | Manufacturing | 2015 |
| Mayer (Teddington) Limited | Wholesale & retail | 2013 |
| Mayfield Care Limited | Health & social care | 2007 |
| Maykind Limited | Real estate | 2023 |
| Mbnd Sport Ltd | Wholesale & retail | 2011 |
| Mbozat Investment Ltd | Real estate | 2024 |
| Mcgsfx Ltd | Information & communication | 2018 |
| Mcsorley Creative Limited | Arts & recreation | 2013 |
| ME WE Films Limited | Information & communication | 2006 |
| Meadows Partnership Limited | Construction | 2003 |
| MEC Motor Consultants Limited | Professional & scientific | 2017 |
| Mechanon Ltd | Wholesale & retail | 2021 |
| Media 360 Limited | Professional & scientific | 2025 |
| Medibell Limited | Other services | 1986 |
| Melbreak Limited | Administrative & support | 2011 |
| Menopause 51 LLP | | 2022 |
| Mentor Engineering Ltd | Construction | 2023 |
| Merchant & General Ltd | Financial services | 2019 |
| Mercurial Mind Ltd | Professional & scientific | 2018 |
| Merganser Communications Ltd | Professional & scientific | 2026 |
| Merriment Atelier Limited | Other services | 2018 |
| Metier Limited | Information & communication | 2015 |
| Metrohall Limited | Professional & scientific | 2008 |
| Mexsom Associates Ltd | Professional & scientific | 2016 |
| MFT Coaching & Consulting Ltd | Professional & scientific | 2025 |
| MFX BIO Tech Ltd | Health & social care | 2012 |
| MG Industrial Hairdressing Ltd | Other services | 2026 |
| Mgmt 4U Ltd | Professional & scientific | 2022 |
| MH Support Services Ltd | Professional & scientific | 2020 |