| Mccullum Holidays Limited | Administrative & support | 2025 |
| Mcdaid Dental Care Ltd | Health & social care | 2013 |
| Mcdevitt Consulting Limited | Professional & scientific | 2013 |
| Mcdonald Simmonds Consulting Ltd | Professional & scientific | 2017 |
| Mcdonalds Flower House Ltd | Wholesale & retail | 2013 |
| Mcdonnell & Gibbons Properties Ltd | Real estate | 2019 |
| Mce-Uk Limited | Professional & scientific | 2025 |
| MCG Claus Ltd | Other services | 2026 |
| Mcgees (UK) Limited | Administrative & support | 2011 |
| Mcgill Plumbing & Heating Ltd | Construction | 2026 |
| Mchaver Associates Limited | Hospitality | 1989 |
| MCI Commercial Ltd | Transport & logistics | 2021 |
| Mcintosh Haulage Limited | Administrative & support | 2014 |
| Mcintyres Driving Tuition Ltd | Education | 2026 |
| Mcis (Trading) UK Ltd | Construction | 2026 |
| Mcjc Investments Ltd | Hospitality | 2020 |
| MCK Global Limited | Administrative & support | 2012 |
| Mckay Property Development Ltd | Construction | 2024 |
| Mckenna Global Services Ltd | Administrative & support | 2018 |
| Mckenzie Friend Solicitors Ltd | Professional & scientific | 2024 |
| Mckie Associates Limited | Information & communication | 1996 |
| Mcknight Safeguarding Ltd | Health & social care | 2013 |
| MCM Optimal Solutions Limited | Professional & scientific | 2021 |
| MCM4ALL Ltd | Transport & logistics | 2024 |
| Mcmahon & Co Hairdressing Ltd | Other services | 2018 |
| Mcmanus Group Limited | Financial services | 2019 |
| Mcmanus Holdings Limited | Hospitality | 2008 |
| Mcmanus Managed PUB Co. Limited | Hospitality | 2000 |
| Mcmanus PUB Co. Limited | Hospitality | 2001 |
| Mcmanus PUB Group Limited | Hospitality | 2014 |
| Mcmanus Taverns Limited | Hospitality | 2009 |
| Mcmar Properties Ltd | Extraterritorial | 2024 |
| Mcmk Properties Limited | Real estate | 2009 |
| Mcmorrow Capital Ltd | Extraterritorial | 2024 |
| Mcmosa Healthcare Ltd | Health & social care | 2022 |
| Mcmullan EYE Care Limited | Health & social care | 2017 |
| Mcmullan Management Services Limited | Real estate | 1999 |
| Mcnally Associates Limited | Administrative & support | 2018 |
| Mcnulty Properties (Lanacre) Limited | Real estate | 2021 |
| Mcnulty Properties Limited | Real estate | 2014 |
| Mcparland Maintenance Limited | Households | 2019 |
| Mcparland Services UK Ltd | Construction | 2015 |
| Mcpave (Northampton) Ltd | Construction | 2014 |
| Mcsandor Limited | Construction | 2019 |
| Mcsk Ltd | Wholesale & retail | 2026 |
| Mcsweeney Property Group Ltd | Real estate | 2024 |
| MCW Consulting Associates LLP | | 2010 |
| MD Autocenter Ltd | Wholesale & retail | 2022 |
| MD Furman Ltd | Real estate | 2020 |
| MD Groundworks & Construction Limited | Construction | 2023 |
| MD LEV Services Limited | Professional & scientific | 2024 |
| MD Projects Data Ltd | Administrative & support | 2009 |
| MD Sims Brickwork Ltd | Construction | 2025 |
| Mdbotanika Ltd | Transport & logistics | 2025 |
| MDE Vision Limited | Health & social care | 2022 |
| Mdmc Construction Ltd | Construction | 2023 |
| Mdmkjb Limited | Professional & scientific | 2013 |
| Mdrive Transport Ltd | Transport & logistics | 2025 |
| MDS Hire Ltd | Administrative & support | 2017 |
| Mdserve Limited | Professional & scientific | 2008 |
| Mdsrl Limited | Construction | 2024 |
| Mdsynergy Ltd | Construction | 2020 |
| MDT Brickwork Ltd | Construction | 2025 |
| MDT Engineering Projects Limited | Professional & scientific | 2015 |
| MDV Projects Limited | Real estate | 2011 |
| Mdva Limited | Hospitality | 2026 |
| MDW Consultants Limited | Professional & scientific | 2016 |
| ME Fire Safety Ltd | Professional & scientific | 2025 |
| Mead Mere LLP | | 2014 |
| Meadow END Property Services Limited | Real estate | 2024 |
| Meadow Interpreting Ltd | Professional & scientific | 2022 |
| Meadow Property Investment Group Limited | Real estate | 2021 |
| Meadow View Fields Management Company Limited | Real estate | 2019 |
| Meadowbrook Care Ltd | Health & social care | 2019 |
| Meadowspire Children's Services Ltd | Health & social care | 2025 |
| Meadowview Investments Limited | Real estate | 2019 |
| Meantime Design Ltd | Professional & scientific | 2018 |
| Mears Ashby Events Co. Ltd | Hospitality | 2025 |
| Meat Craft Limited | Manufacturing | 2024 |
| Mebo Technologies Ltd | Information & communication | 2024 |
| Mebrof&F Ltd | Wholesale & retail | 2019 |
| Mecasu (Property) Ltd | Real estate | 2025 |
| Medalstandard Limited | Information & communication | 2014 |
| Medawi Ltd | Health & social care | 2021 |
| Medeagle Limited | Health & social care | 2024 |
| Medeea Services Ltd | Transport & logistics | 2017 |
| Medelin Trans Ltd | Transport & logistics | 2017 |
| Medexcel Enterprises UK Ltd | Real estate | 2009 |
| Media 786 Group Ltd | Information & communication | 2024 |
| Media Colour Solutions Limited | Manufacturing | 2012 |
| Media House Management Limited | Real estate | 2024 |
| Media Marketing Matters Limited | Professional & scientific | 2023 |
| Median Wellness Ltd | Health & social care | 2017 |
| Medical Network Recruitment Limited | Administrative & support | 2023 |
| Medical Republic Ltd | Wholesale & retail | 2018 |
| Medicare-Ed Ltd | Real estate | 2022 |
| Medigold Health Consultancy Limited | Health & social care | 1998 |
| Medigold HML Holdings Limited | Financial services | 2008 |
| Medigold Limited | Extraterritorial | 1998 |
| Medigold Occupational Health Limited | Extraterritorial | 2006 |