| MDS Trans Ltd | Transport & logistics | 2016 |
| MDS Trustees Limited | Professional & scientific | 2017 |
| ME Accountancy Ltd | Professional & scientific | 2018 |
| ME and BEA Limited | Wholesale & retail | 2021 |
| Meadean Limited | Professional & scientific | 2003 |
| Meadow Plastics Ltd | Transport & logistics | 2018 |
| Meadows & Co Limited | Professional & scientific | 1994 |
| Meadows Nominees Limited | Extraterritorial | 2007 |
| Meadows WR LLP | | 2007 |
| Meals by Muganiwa Ltd | Hospitality | 2026 |
| Mechanical Pipework Services (Kettering) Ltd | Construction | 2018 |
| Mechanical Systems UK Limited | Administrative & support | 2001 |
| Mechanicalconsulting Ltd | Professional & scientific | 2023 |
| Media Lease Limited | Financial services | 2001 |
| Mediclinic GP Ltd | Health & social care | 2024 |
| Medisec Limited | Administrative & support | 2021 |
| Medlenna Limited | Information & communication | 2026 |
| Medpage Limited | Manufacturing | 2005 |
| Meenz Recruitment Limited | Administrative & support | 2016 |
| Meeting Lane Development BA Limited | Construction | 2019 |
| Mega Bounce Park Ltd | Arts & recreation | 2025 |
| Mega Group Holdings Limited | Real estate | 2021 |
| Mega Resources Limited | Professional & scientific | 2011 |
| MEGA212FOOD Limited | Wholesale & retail | 2026 |
| Megan Robinson Personal Training Ltd | Arts & recreation | 2019 |
| Melius Homes Limited | Construction | 2016 |
| Mellor Gardner Limited | Real estate | 2017 |
| Melmasons Healthcare Ltd | Health & social care | 2017 |
| Meluba Limited | Wholesale & retail | 2006 |
| MEM Property Investments Limited | Real estate | 2025 |
| Mental Health Northants Collaboration | Health & social care | 2014 |
| Mepat Limited | Other services | 2015 |
| Merchandising for Life Limited | Arts & recreation | 1995 |
| Merger Investments Limited | Professional & scientific | 1956 |
| Meridian Bell Limited | Professional & scientific | 2019 |
| Meridian Rugs Ltd | Wholesale & retail | 2025 |
| Meridiantransport Ltd | Construction | 2019 |
| Merifra (UK) Limited | Real estate | 2003 |
| Merrilees Holdings Limited | Financial services | 2025 |
| Merrilees Industries Limited | Financial services | 2024 |
| Merrilees Investments Limited | Real estate | 2025 |
| Merrilees LLP | | 2025 |
| Merrj Limited | Extraterritorial | 2021 |
| Mersault Managers Limited | Households | 1993 |
| Messy Services Limited | Real estate | 2021 |
| Metamorphosis Care Ltd | Health & social care | 2018 |
| Metcalf Commercial Projects Limited | Construction | 2026 |
| Metra Design Ltd | Administrative & support | 2008 |
| Metro Removals Ltd | Transport & logistics | 1982 |
| Metta Spaces Ltd | Real estate | 2022 |
| Mexican Fire Garden Ltd | Hospitality | 2018 |
| MF Utility Limited | Information & communication | 2022 |
| MG Doctors Limited | Health & social care | 2024 |
| MG Electrical (Desborough) Limited | Construction | 2012 |
| MGA Property Investment Ltd | Real estate | 2020 |
| Mgexcelence Ltd | Professional & scientific | 2025 |
| MGJ Transport Ltd | Transport & logistics | 2022 |
| MGM Bathrooms Ltd | Wholesale & retail | 2020 |
| MGM Products Limited | Wholesale & retail | 2009 |
| MGO Property Care Limited | Construction | 2025 |
| MGO Solutions Limited | Construction | 2016 |
| Mgvc Limited | Health & social care | 2016 |
| MH Consulting Services Ltd | Real estate | 2024 |
| MHS Business Ltd | Wholesale & retail | 2024 |
| MI Property Holdings Ltd | Real estate | 2024 |
| MIB Rentals Limited | Real estate | 2023 |
| Michael Campbell Golf Ltd | Wholesale & retail | 2019 |
| Michael Garrett Limited | Administrative & support | 2011 |
| Michael Harris Homes Limited | Construction | 2007 |
| Michael Wilkinson Plastering and General Services Limited | Administrative & support | 2014 |
| Michan Builders Limited | | 1979 |
| Mickey's Limited | Professional & scientific | 2013 |
| Microlesh Ltd | Health & social care | 2022 |
| MICROMAN2000 Limited | Information & communication | 1998 |
| MID Logistics Ltd | Transport & logistics | 2024 |
| Middlewest House Management Company Ltd | Other services | 2017 |
| Midland Builds Limited | Construction | 2025 |
| Midland Forklifts Limited | Extraterritorial | 1980 |
| Midland Mechanical Engineers Limited | Other services | 2011 |
| Midland Pallets Limited | Manufacturing | 1975 |
| Midland Plant Sales Ltd | Other services | 2020 |
| Midlands Airsoft Wargames Limited | Arts & recreation | 2014 |
| Midlands Pond Services Limited | Construction | 2018 |
| Midlands Services Ltd | Other services | 2014 |
| Midsummer Drylining Limited | Construction | 2016 |
| Midsummer Fire Protection Ltd | Administrative & support | 2018 |
| Mighty Rides Limited | Wholesale & retail | 2025 |
| Mihai Razvan Ltd | Transport & logistics | 2019 |
| Mike Green Media Limited | Professional & scientific | 2019 |
| Milan Express Limited | Administrative & support | 2013 |
| Milestone Design Services Limited | Information & communication | 1998 |
| Milestones Education Services Limited | Education | 2020 |
| Milex Plus Ltd | Transport & logistics | 2024 |
| Milfab Ltd | Manufacturing | 2021 |
| Mill Rose Tree Services Limited | Agriculture & fishing | 2025 |
| Millennium Group Partnership LLP | | 2019 |
| Millennium Partner Ltd | Real estate | 2019 |
| Millie Development BA Limited | Construction | 2018 |
| Millies Garden Design & Floristry Ltd | Wholesale & retail | 2021 |
| Milling Garden Services Limited | Administrative & support | 2024 |