| Marchpack Ltd | Other services | 2018 |
| Marcon LEE Limited | Construction | 2018 |
| Marcone Couriers Ltd | Wholesale & retail | 2017 |
| Marcus Trading Ltd | Administrative & support | 2004 |
| Margaret Ashton-Gray Consulting Ltd | Professional & scientific | 2018 |
| Maria Locum Ltd | Health & social care | 2026 |
| Maribella London Limited | Manufacturing | 2017 |
| Maricel Ltd | Financial services | 2024 |
| Marigold Professional Drycleaners Ltd | Administrative & support | 2026 |
| Marilyns Limited | Transport & logistics | 2018 |
| Marine Properties Limited | Real estate | 2001 |
| Marino's Fish Bar Bearsted Limited | Hospitality | 2018 |
| Mark Bentley Ltd | Real estate | 2018 |
| Mark Brayton Ltd | Professional & scientific | 2019 |
| Mark D Hick & Associates Limited | Other services | 2016 |
| Mark Tonks & Associates Limited | Professional & scientific | 2006 |
| Market Location Limited | Information & communication | 1984 |
| Market Location Secure Ltd | Information & communication | 2013 |
| Marketing Moves UK Limited | Real estate | 1996 |
| Markham Estates and Lettings Limited | Real estate | 2023 |
| Markpp Financial Services Consultancy Ltd | Financial services | 2020 |
| Marleybrook Limited | Information & communication | 2019 |
| Marleyford Limited | Health & social care | 2018 |
| Marlia Ltd | Administrative & support | 2013 |
| Marlo Property Management Limited | Real estate | 2020 |
| Maroon Creative Spaces Ltd | Construction | 2025 |
| Marresta Holdings Limited | Financial services | 2026 |
| Mars Solutions Ltd | Other services | 2019 |
| Marshfield Gardens Management Company Limited | Other services | 1994 |
| Marston Fields Fishery Ltd | Agriculture & fishing | 2022 |
| Marston Motors Limited | Wholesale & retail | 2019 |
| Mart Consultancy Limited | Professional & scientific | 2020 |
| Martialwear-Uk Ltd | Wholesale & retail | 2021 |
| Martin Anderson Limited | Professional & scientific | 2005 |
| Martin Diamonds Accountants ( MDA) Limited | Professional & scientific | 2019 |
| Martin Pitt Associates Limited | Professional & scientific | 2020 |
| Martin Ward & Keeling Limited | Professional & scientific | 2002 |
| Martin Watson Consulting Ltd | Professional & scientific | 2022 |
| Martius (Holdings) Limited | Financial services | 2009 |
| Marvel P N Properties Ltd | Real estate | 2020 |
| Marvellous Mindset Ltd | Other services | 2017 |
| Marvin Consulting Limited | Information & communication | 2011 |
| Marwood Surveyors Limited | Real estate | 2013 |
| Marwyn Investments Limited | Financial services | 2017 |
| Maryam Catering Limited | Hospitality | 2025 |
| MAS Chapman Frcs Ltd | Health & social care | 2001 |
| Masih Consultancy Limited | Professional & scientific | 2020 |
| Mason Building Services ( Midland) Limited | Construction | 2023 |
| Mason Funeral Service Limited | Extraterritorial | 1991 |
| Masonsafe Ltd | Professional & scientific | 2026 |
| Massa Property Holdings Limited | Real estate | 2019 |
| Massey Construction & Residential Limited | Construction | 2025 |
| Master Glass Artists Limited | Manufacturing | 2009 |
| Master Tyres Ltd | Wholesale & retail | 2020 |
| Masterplan Financial Ltd | Financial services | 2015 |
| Masterplan Wealth Holdings Ltd | Financial services | 2021 |
| Masterplan Wealth Ltd | Extraterritorial | 2019 |
| Mates Rates Horse Transport International Limited | Transport & logistics | 2021 |
| Mates Rates Horse Transport Limited | Extraterritorial | 2023 |
| Matheson Properties Limited | Real estate | 2025 |
| Mathias's of Putney Limited | Extraterritorial | 1949 |
| Mathon Associates Limited | Professional & scientific | 2011 |
| Matilda Homes Limited | Real estate | 2019 |
| Matrix Group 786 Ltd | Hospitality | 2021 |
| MATT4GAS Limited | Construction | 2023 |
| Matthew Moore Associates Limited | Professional & scientific | 2001 |
| Matthew Phillips Surveyors Limited | Real estate | 2006 |
| Mattwill Ltd | Construction | 2012 |
| Mauve Design Limited | Information & communication | 2004 |
| MAV 18 Limited | Administrative & support | 2017 |
| Mawi Ltd | Information & communication | 2025 |
| MAX Mini Mart Ltd | Wholesale & retail | 2025 |
| Maxell FM Ltd | Extraterritorial | 2014 |
| Maxol Limited | Mining & quarrying | 2018 |
| Maxs Coffee Shop Limited | Hospitality | 2017 |
| Maxstoke Investments Limited | Professional & scientific | 2025 |
| Maxwell Bros,Limited | Extraterritorial | 1892 |
| Maya Designs and Build Ltd | Construction | 2024 |
| Maybrook SC Limited | Construction | 2024 |
| Mayhew Walker Consulting Limited | Professional & scientific | 2026 |
| MAZ (Midlands) Limited | Real estate | 2010 |
| Mazina Investments Limited | Financial services | 2011 |
| Mazzameals Ltd | Hospitality | 2020 |
| MBC Electrical Services Limited | Construction | 2016 |
| MC Contracting Services Limited | Construction | 2024 |
| MC Digital Advisory Limited | Professional & scientific | 2024 |
| MC Education (West Midlands) Ltd | Professional & scientific | 2021 |
| MC Inspired Ltd | Wholesale & retail | 2025 |
| Mcbolger Coaching & Consultancy Limited | Professional & scientific | 2019 |
| Mcbrine Structures (Civil Engineering) Limited | Construction | 1998 |
| Mcbrine Structures (Midlands) Limited | Construction | 1995 |
| MCC2 Ltd | Administrative & support | 2025 |
| Mccann Eades Limited | Wholesale & retail | 2004 |
| Mccartney Delaney Services Limited | Wholesale & retail | 1992 |
| Mccl Consultancy Ltd | Information & communication | 2014 |
| Mccoy Fitness Limited | Other services | 2025 |
| Mcdonagh Estates Ltd | Real estate | 2021 |
| Mcenery Financial Solutions Limited | Professional & scientific | 2024 |
| Mcgee Associates Limited | Professional & scientific | 2010 |
| Mcgheesbarwolverhampton Limited | Hospitality | 2023 |