| Marian Serv Ltd | Manufacturing | 2019 |
| Marina Transport Ltd | Transport & logistics | 2025 |
| Marine and Special Operations Ltd | Administrative & support | 2019 |
| Marine Capability Solutions Limited | Manufacturing | 2016 |
| Marioni Ltd | Construction | 2025 |
| Marius NCK Ltd | Transport & logistics | 2018 |
| Mark Bell Properties Ltd | Real estate | 2022 |
| Mark Fiddes Tree Works Ltd | Agriculture & fishing | 2008 |
| Mark Smith Investments Ltd | Real estate | 2025 |
| Mark Waller Limited | Construction | 2015 |
| Markalph Group Ltd | Other services | 2024 |
| Market Barakat Ltd | Wholesale & retail | 2026 |
| Market Square (ST Georges) Management Company Limited | Households | 2003 |
| Marley House Ltd | Manufacturing | 2011 |
| Marquee Labour Solutions Ltd | Construction | 2018 |
| Martin Stidwell Building Contractors Ltd | Construction | 2014 |
| Maruso Recruitment Limited | Administrative & support | 2023 |
| Marvel Roofing and Building Services Ltd | Construction | 2020 |
| Marvelbines Ltd | Wholesale & retail | 2025 |
| Mashal Global Ltd | Arts & recreation | 2025 |
| Masilela Ltd | Health & social care | 2014 |
| Masiza Wellness Limited | Health & social care | 2023 |
| Massi Health Ltd | Health & social care | 2026 |
| Master of ALL Trades Limited | Construction | 2020 |
| Masters Portfolio Ltd | Real estate | 2021 |
| Matilda Healthcare Limited | Health & social care | 2016 |
| Matt Culpin Roofing Ltd | Construction | 2025 |
| Matthew FOX Coaching and Therapy Services Limited | Health & social care | 2018 |
| Maurice Fitz George Ltd | Construction | 2017 |
| Maverick Resources Limited | Hospitality | 2010 |
| Maxbay Products Ltd | Manufacturing | 2023 |
| Maxmus Limited | Health & social care | 2024 |
| Maxwell Automotive Ltd | Wholesale & retail | 2014 |
| Maxxi Save WSM Ltd | Wholesale & retail | 2022 |
| Maycock Properties Limited | Real estate | 2022 |
| Mayfair Associates & Consultancy Limited | Professional & scientific | 2008 |
| Mayfields Consulting Ltd | Information & communication | 2023 |
| Mazescape Ltd | Professional & scientific | 2008 |
| MB & AB Property Company Limited | Real estate | 2020 |
| MBD IT Consulting Limited | Information & communication | 2016 |
| Mbinze Mesame Limited | Health & social care | 2025 |
| MC Distribution Ltd | Transport & logistics | 2010 |
| MC QS Services Ltd | Professional & scientific | 2017 |
| MCC Management Services Ltd | Real estate | 2001 |
| Mcleod Transport (SW) Limited | Transport & logistics | 2019 |
| MCR + R Ltd | Construction | 2020 |
| MD Construction (South West) Ltd | Construction | 2025 |
| MD Technical Design Ltd | Professional & scientific | 2021 |
| MDC Trans Limited | Transport & logistics | 2025 |
| Mdescaya Ltd | Health & social care | 2024 |
| MDPROPERTY22 Ltd | Real estate | 2022 |
| MDS Domestic Heating Limited | Construction | 2026 |
| ME Eclipse Entertainments Ltd | Administrative & support | 2025 |
| Mead Construction Limited | Professional & scientific | 2015 |
| Mead Homes (SW) Limited | Construction | 2020 |
| Mead Vale Shops (Management) Limited | Real estate | 1977 |
| Meadow Court (W-S-M) Management Company Limited | Households | 1990 |
| Meadows Property Investments Ltd | Financial services | 2021 |
| Meda Dumitru Limited | Administrative & support | 2016 |
| Mediaverts Advertising Limited | Professional & scientific | 2024 |
| Medigoals Ltd | Education | 2025 |
| Mediwise Health Advice Limited | Financial services | 2025 |
| Mediz Limited | Health & social care | 2020 |
| Medlar Tree Ltd | Agriculture & fishing | 2011 |
| Medusa Resources Limited | Financial services | 2017 |
| Meet UP Limited | Real estate | 2018 |
| Melosome Group Ltd | Information & communication | 2025 |
| Meltdown Fighting Championships Ltd | Arts & recreation | 2024 |
| Memorable Moments Limited | Education | 2012 |
| Memory Lane Ice Cream Ltd | Hospitality | 2023 |
| Mendip Edge Construction Ltd | Construction | 2026 |
| Mendip Gate Management Company Limited | Households | 2020 |
| Mercer Consulting Associates Limited | Professional & scientific | 2018 |
| Merchant Rose Limited | Administrative & support | 2003 |
| Merrivaile Limited | Real estate | 2016 |
| Merrywood Management Company Limited | Households | 2020 |
| Merset Media Ltd | Information & communication | 2019 |
| Merton Place Residents Limited | Households | 2004 |
| Meta-Tag Ltd | Information & communication | 2023 |
| Metclean Ltd | Wholesale & retail | 2024 |
| Metford Limited | Extraterritorial | 2011 |
| MFA Developments Ltd | Construction | 2020 |
| Mgcini Limited | Health & social care | 2021 |
| Mgoldfinch Ltd | Transport & logistics | 2016 |
| MH Computer Systems Ltd | Professional & scientific | 2022 |
| MH Contractors Southwest Ltd Ltd | Construction | 2026 |
| MH Electrical Southwest Ltd | Construction | 2015 |
| MH Roofing Solutions Ltd | Construction | 2024 |
| MHA Solutions Ltd | Professional & scientific | 2014 |
| MHC Storage Limited | Transport & logistics | 2019 |
| MHD Property Solutions Ltd | Real estate | 2019 |
| MI Envelope Specialists Ltd | Construction | 2018 |
| MIB Plumbing & Tiling Ltd | Construction | 2023 |
| Michael Driver Ltd | Transport & logistics | 2016 |
| Michaelaki Estates Limited | Construction | 2017 |
| Michal a Czerwinski Ltd | Transport & logistics | 2024 |
| Michal Bochynski Ltd | Financial services | 2021 |
| Michal Dajer Ltd | Wholesale & retail | 2020 |
| Michelle Owen Media Ltd | Information & communication | 2025 |
| Micro Clutch Developments Limited | Administrative & support | 1978 |