| Mayferry Ltd | Information & communication | 2026 |
| Mayford Conservatories and Windows Limited | Administrative & support | 2003 |
| Mayford Hand Car Wash Ltd | Wholesale & retail | 2026 |
| Mayford James Limited | Administrative & support | 2010 |
| Mayford Mechanical Services Ltd | Construction | 2018 |
| Mayrobert Ltd | Hospitality | 2023 |
| Mazhar Holdings Limited | Real estate | 2018 |
| Mazzi Ltd | Other services | 2002 |
| Mazzy Bees Soft Play Limited | Health & social care | 2025 |
| MB Car Centre Ltd | Wholesale & retail | 2025 |
| MB Dynamic Services Ltd | Construction | 2024 |
| MB Landscapes & Paving Ltd | Administrative & support | 2026 |
| MB Roofing (Chessington) Limited | Construction | 2015 |
| MB1 Properties Limited | Real estate | 2013 |
| MBA (Surrey) Ltd | Professional & scientific | 2022 |
| MBR Wealth Management Limited | Professional & scientific | 2009 |
| MBS Sports Network Limited | Information & communication | 2025 |
| Mcaa Limited | Health & social care | 2022 |
| Mccarthy Bainbridge Limited | Professional & scientific | 1973 |
| Mccrarren FD Consultancy Services Ltd | Professional & scientific | 2020 |
| Mcglashan Building & Property Services Limited | Construction | 2025 |
| Mcgregor Technology Limited | Information & communication | 2014 |
| Mckennaella Limited | Hospitality | 2025 |
| MCL Services Limited | Construction | 1997 |
| Mclaren Automotive Events Limited | Arts & recreation | 2015 |
| Mclaren Automotive Holdings Limited | Other services | 2017 |
| Mclaren Automotive Limited | Manufacturing | 1985 |
| Mclaren Electric Racing Limited | Arts & recreation | 2017 |
| Mclaren Finance PLC | Other services | 2017 |
| Mclaren Group Limited | Financial services | 2017 |
| Mclaren Heritage Cars Newco Limited | Financial services | 2026 |
| Mclaren Marketing Limited | Extraterritorial | 1985 |
| Mclaren Newco (NO.2) Limited | Financial services | 2023 |
| Mclaren Newco Limited | Other services | 2021 |
| Mclaren PM Limited | Real estate | 2024 |
| Mclaren Racing Limited | Arts & recreation | 1980 |
| Mclaren Services Limited | Financial services | 1985 |
| Mclaren Support Services Limited | Financial services | 2020 |
| Mclaren Triple Crown Limited | Financial services | 2021 |
| Mcpettet Consultancy Limited | Professional & scientific | 2022 |
| Mcpg Ltd | Professional & scientific | 2012 |
| Mcqueen Embroidery Ltd | Wholesale & retail | 2022 |
| MCS Building Consultants Limited | Construction | 2005 |
| Mcshiells Consulting Ltd | Administrative & support | 2020 |
| MD Heating & Plumbing Surrey Limited | Construction | 2016 |
| Mdhkach Ltd | Health & social care | 2024 |
| Mdrclarity Limited | Financial services | 2012 |
| MDS Engineering and Construction Ltd | Construction | 2025 |
| MEA Opus Limited | Administrative & support | 2023 |
| Meadow Sports and Old Wokingians Limited | Arts & recreation | 1986 |
| Meadows WYE Container Groupage Limited | Transport & logistics | 1974 |
| Meat @ Jay's Ltd | Hospitality | 2020 |
| MEC Employee Benefits Limited | Financial services | 2015 |
| Mech Medic Ltd | Wholesale & retail | 2024 |
| MED & DOC Ltd | Real estate | 2021 |
| MED4LEX Limited | Health & social care | 2025 |
| Medco Properties Limited | Other services | 2014 |
| Medeikon Ltd | Information & communication | 2000 |
| Medgett Consulting Ltd | Professional & scientific | 2023 |
| Media & Technology Consultancy Limited | Information & communication | 2024 |
| Media Business Solutions (UK) Ltd. | Professional & scientific | 2014 |
| Media Forge Ltd | Information & communication | 2024 |
| Media Make-Up Services Limited | Education | 1999 |
| Medicines Professionals Ltd | Manufacturing | 2021 |
| Mediclarity Limited | Professional & scientific | 2022 |
| Medishield | Extraterritorial | 1918 |
| Medispeed | Professional & scientific | 2007 |
| Mediteria Limited | Wholesale & retail | 2004 |
| Medscontractor Ltd | Health & social care | 2023 |
| Meet the Pods Ltd | Manufacturing | 2018 |
| Meis Limited | Professional & scientific | 1997 |
| Melissa Oldridge Ltd | Other services | 2018 |
| Melo-Velo Ltd | Wholesale & retail | 2024 |
| Mendip (UK) Ltd | Hospitality | 2013 |
| Meno Recollections Limited | Information & communication | 2002 |
| Mentum Limited | Professional & scientific | 2018 |
| Merake Ltd | Manufacturing | 2025 |
| Merana Limited | Professional & scientific | 2018 |
| Mercer Planning Recruitment Ltd | Professional & scientific | 2016 |
| Merchant and Traders Alresford Ltd | Construction | 2020 |
| Merchant and Traders Limited | Construction | 2017 |
| Merchants Court Management Company Limited | Households | 2002 |
| Mercian Sports Company Limited | Wholesale & retail | 1981 |
| Mercian Travel Limited | Administrative & support | 2024 |
| Merisien Merisior Ltd | Wholesale & retail | 2025 |
| Mesmotronic Limited | Information & communication | 2005 |
| Messenger Pigeon Ltd | Manufacturing | 2003 |
| Mesuva Ltd | Information & communication | 2021 |
| Meta E-Shop Ltd | Wholesale & retail | 2022 |
| Metaversed Ltd | Information & communication | 2022 |
| Metea Chauffeuring Ltd | Transport & logistics | 2018 |
| Metis Projects Ltd | Administrative & support | 2017 |
| Metisak Limited | Information & communication | 2017 |
| Metrix Associates Limited | Health & social care | 2012 |
| Metrobuild Solutions Ltd | Construction | 2025 |
| Metrophonic Music Limited | Information & communication | 2001 |
| Metrophonic Productions Limited | Information & communication | 2003 |
| Metrophonic Records Limited | Information & communication | 2007 |
| Mews Design Limited | Construction | 2013 |
| Mexfield Limited | Professional & scientific | 2020 |