| Mbda International Limited | Professional & scientific | 2003 |
| Mbda UAE Limited | Manufacturing | 1949 |
| Mbhj Rigging Ltd | Construction | 2024 |
| MC Catering Services Ltd | Wholesale & retail | 2025 |
| Mc&Lc Transport Ltd | Transport & logistics | 2025 |
| Mcbrien Management Ltd | Construction | 2023 |
| Mccabe Accounting Limited | Professional & scientific | 2020 |
| Mccarthy Digital Marketing Ltd | Professional & scientific | 2024 |
| Mccarthy Transport Services Ltd | Transport & logistics | 2018 |
| Mcclure Preclinical Consultancy Ltd | Professional & scientific | 2026 |
| Mccolm Brickwork Limited | Construction | 2023 |
| Mcdalavan Homes Limited | Real estate | 2024 |
| Mcfs Care Services Limited | Administrative & support | 2013 |
| Mcgilley Holdings Limited | Financial services | 2021 |
| Mcgilley Properties Limited | Other services | 2024 |
| Mcgu’S Booze Ltd | Hospitality | 2024 |
| Mcj&J Care Ltd | Health & social care | 2021 |
| MCK Property Solutions Limited | Real estate | 2018 |
| Mcloughlin Competency Assessment Ltd | Education | 2025 |
| Mcmanus Property Solutions Limited | Real estate | 2024 |
| MCN Group Developments Limited | Real estate | 2024 |
| MCN Group Limited | Construction | 2020 |
| Mcnaught Limited | Health & social care | 2019 |
| MCT Construction Limited | Construction | 2012 |
| MDB (Holdings) Limited | Financial services | 1999 |
| Mdco&A Limited | Information & communication | 2025 |
| Mdconstruct Builders Ltd | Construction | 2020 |
| MDL Trans Ltd | Administrative & support | 2018 |
| MDM Plus Limited | Real estate | 2019 |
| MDP Construction Ltd | Construction | 2017 |
| MDS Line Limited | Wholesale & retail | 2025 |
| ME Properties London Limited | Real estate | 2018 |
| Mead Lane Hertford Management Limited | Households | 2008 |
| Meadfleet Limited | Real estate | 1995 |
| Meadow Croft Glamping Limited | Hospitality | 2026 |
| Meadowlands (NO.1) Residents Association Limited | Households | 2003 |
| Measured Madness Ltd | Construction | 2026 |
| Mechanical & Electrical Contractors Ltd | Manufacturing | 2022 |
| Mechanical & Electrical Engineering Limited | Manufacturing | 2018 |
| Mechanical Production Engineers Ltd | Professional & scientific | 2018 |
| Mechatronics PVT Ltd | Professional & scientific | 2026 |
| Mecure Value Care Ltd | Health & social care | 2026 |
| Med-Infinite Ltd | Information & communication | 2024 |
| Meddy Estate Ltd | Households | 2023 |
| Media Alive Limited | Professional & scientific | 2011 |
| Media Chameleon Limited | Information & communication | 1982 |
| Media Dudes USA Limited | Professional & scientific | 2021 |
| Media Select Ltd | Professional & scientific | 2024 |
| Mediacom 24-7 Travel Limited | Administrative & support | 2017 |
| Mediconnect BC Limited | Administrative & support | 2018 |
| Medlife Healthcare Limited | Health & social care | 2016 |
| Meemo's Motors Ltd | Wholesale & retail | 2024 |
| Meems Cleans Ltd | Administrative & support | 2025 |
| Meikles Construction Consultants Ltd | Administrative & support | 2026 |
| Meikosoft Limited | Information & communication | 2025 |
| Melai's Foodie Bytes Ltd | Manufacturing | 2026 |
| Melo Healthcare Services Ltd | Health & social care | 2019 |
| Melody Grill Ltd | Hospitality | 2023 |
| Melos Properties Ltd | Real estate | 2023 |
| Melton Court (Dunstable) Management Co. Limited | Households | 1973 |
| Memec Group Holdings Limited | Professional & scientific | 2000 |
| Memec Group Limited | Financial services | 2000 |
| Memoauto Limited | Wholesale & retail | 2024 |
| Mems Consultancy Limited | Professional & scientific | 2025 |
| Mena Space Ltd | Professional & scientific | 2021 |
| Mendes Legal Services Ltd | Financial services | 2024 |
| Mendip Lodge Residents Association Limited | Real estate | 2010 |
| Mendip Way Limited | Households | 2008 |
| Menon and Kumar Healthcare Limited | Health & social care | 2020 |
| Mentor Services (Investments) Limited | Real estate | 2024 |
| Mentor Services Management Limited | Real estate | 2022 |
| MEP Contractors Limited | Construction | 2019 |
| Merano Pizza Ltd | Wholesale & retail | 2023 |
| Merano Pizzeria Ltd | Hospitality | 2026 |
| Mercer Interiors Ltd | Construction | 2021 |
| Merchant Hub Limited | Financial services | 2009 |
| Mercy Estates Ltd | Real estate | 2023 |
| Mercy Ships - U.K. Limited | Health & social care | 1996 |
| Meridian Gate Residents Association Limited | Households | 2000 |
| MES Commercial Limited | Construction | 2021 |
| MET Construction Group Limited | Construction | 2019 |
| Metal Fusion Limited | Construction | 2002 |
| Metalcraft Fabrication Limited | Construction | 1997 |
| Metric Envelopes Limited | Wholesale & retail | 2004 |
| Metrr Health Limited | Health & social care | 2025 |
| Meyv Limited | Health & social care | 2025 |
| MF Construction Projects Limited | Construction | 2014 |
| MG Property Maintenance Limited | Construction | 2013 |
| Mg-Band Ltd | Construction | 2014 |
| MGC Live Ltd | Wholesale & retail | 2025 |
| MGC Retail Ltd | Wholesale & retail | 2026 |
| MGD Project Management Limited | Professional & scientific | 2013 |
| Mgjp Stevenage Limited | Education | 2025 |
| MGL 1982 Ltd | Construction | 2015 |
| MGM Cars (Northern) Limited | Information & communication | 1999 |
| Mgmk Limited | Information & communication | 1999 |
| Mgmr Ltd | Administrative & support | 2009 |
| MGN Family Investment Ltd | Real estate | 2025 |
| Mgodi Netsai Limited | Health & social care | 2012 |
| Mgray Limited | Health & social care | 2021 |