| Mermaa Properties Ltd | Real estate | 2022 |
| Merrick Contracting Limited | Agriculture & fishing | 2020 |
| Merryfield Leisure Limited | Hospitality | 1950 |
| Merrytide Limited | Professional & scientific | 2018 |
| Merryweather Property Investments Limited | Real estate | 2025 |
| Mert Trading Ltd | Wholesale & retail | 2015 |
| Merula Limited | Information & communication | 1996 |
| Merys Cakes Ltd | Manufacturing | 2020 |
| Metaboo Ltd | Information & communication | 2022 |
| Metaflask Ltd | Wholesale & retail | 2024 |
| Metalco SPS Limited | Water & waste | 2006 |
| Metalforce Limited | Manufacturing | 1991 |
| Metbio Scientific Consulting Limited | Professional & scientific | 2023 |
| Meteor Homes Limited | Real estate | 2020 |
| Metkon Investments Ltd | Real estate | 2021 |
| Metkon Ltd | Construction | 2012 |
| Metos UK Ltd | Agriculture & fishing | 2018 |
| Metro Property Investors Ltd | Real estate | 2026 |
| Mettaworld Ltd | Wholesale & retail | 2019 |
| Mettoline Ltd | Wholesale & retail | 2025 |
| Mewjcan Ltd. | Professional & scientific | 2018 |
| Mexi One Ltd | Financial services | 2025 |
| Mexipark Limited | Financial services | 2017 |
| MF Care Ltd | Health & social care | 2024 |
| MF Motors Ltd | Wholesale & retail | 2022 |
| MF Project Management Limited | Construction | 2025 |
| MFA Associates Ltd | Health & social care | 2023 |
| MFB Holdings Ltd | Financial services | 2025 |
| Mfco UK Limited | Education | 2014 |
| MFM Sales Ltd | Wholesale & retail | 2023 |
| MFN Business Management Services Ltd | Professional & scientific | 2015 |
| MFS Motor Group Ltd | Wholesale & retail | 2025 |
| MFT GAS Service Ltd | Construction | 2024 |
| MFZ Testing Limited | Information & communication | 2012 |
| MG & Sons (Consultancy) Ltd | Construction | 2019 |
| MG Bars & Pubs Ltd | Hospitality | 2025 |
| MG Electrical (Grantham) Ltd | Manufacturing | 2014 |
| MG Executive Cleaners Ltd | Transport & logistics | 2025 |
| MG GET Invest + LLP | | 2026 |
| MG GET Invest Ltd | Administrative & support | 2024 |
| MG Hayward Limited | Health & social care | 2022 |
| MG Muraru Courier Ltd | Transport & logistics | 2021 |
| MG Partitions & Ceilings Limited | Construction | 2011 |
| MG Pro Leather Specialist Ltd | Wholesale & retail | 2022 |
| Mg&Lm Properties Ltd | Real estate | 2022 |
| Mg&Sons Holdings Ltd | Financial services | 2025 |
| Mgch (Peterborough) Limited | Financial services | 2011 |
| MGG Transport Ltd | Transport & logistics | 2024 |
| Mgig Resources Ltd | Health & social care | 2016 |
| Mgmedia Services Limited | Professional & scientific | 2003 |
| MGN Transport Ltd | Transport & logistics | 2018 |
| MGR Global Trade Limited | Manufacturing | 2025 |
| Mgr-Trans Ltd | Transport & logistics | 2019 |
| Mgtek Ltd | Administrative & support | 2017 |
| Mgtj Properties Limited | Real estate | 2024 |
| MH Autos Peterborough Ltd | Wholesale & retail | 2011 |
| MH Cutz Ltd | Other services | 2023 |
| MH Driving School Peterborough Ltd | Education | 2023 |
| MH Facilities Management Ltd | Administrative & support | 2026 |
| MH Network Limited | Information & communication | 2025 |
| MHG Property Maintenance Ltd | Construction | 2019 |
| MHL Developments Ltd | Real estate | 2026 |
| MHL Technologies Ltd | Other services | 2014 |
| Mhrs Thanki Enterprise Limited | Real estate | 2023 |
| MHS Media Ltd | Information & communication | 2024 |
| Mhs.Com Limited | Wholesale & retail | 2004 |
| Mhzstudios Ltd | Arts & recreation | 2022 |
| MI IZ Ltd | Wholesale & retail | 2025 |
| MI Masterchef Ltd | Hospitality | 2023 |
| MIA Construct and Build Limited | Construction | 2023 |
| MIA Homes Group Limited | Administrative & support | 2023 |
| MIA Mcaughtrie Ltd | Health & social care | 2018 |
| MIA Shop 2003 Limited | Wholesale & retail | 2025 |
| MIA Staff Employment Ltd | Administrative & support | 2021 |
| Miakhil Urology Limited | Health & social care | 2020 |
| Mibin Limited | Manufacturing | 2019 |
| MIC Services Ltd | Construction | 2019 |
| Micadi Ltd | Construction | 2025 |
| Micbol Limited | Health & social care | 2025 |
| Mich BUD Ltd | Transport & logistics | 2014 |
| Michael Haulage Ltd | Transport & logistics | 2022 |
| Michael Taylor Close Limited | Real estate | 2014 |
| Michael Vincent Consulting Limited | Extraterritorial | 2013 |
| Michael Wright Consultancy Limited | Education | 2013 |
| Michtech Contractors Ltd | Construction | 2021 |
| Mick Stewart Limited | Hospitality | 2020 |
| Mickle Management LLP | | 2011 |
| Microbyte Ltd | Professional & scientific | 2025 |
| Microbyte Solutions Limited | Other services | 2002 |
| Microquip Ltd | Wholesale & retail | 2025 |
| Micutzu Transport Ltd | Administrative & support | 2015 |
| Mid-Anglia Flight Centre Limited | Arts & recreation | 1998 |
| Midas Renovation Ltd | Construction | 2025 |
| Midas Staffing Group Ltd | Administrative & support | 2026 |
| Midas Touch Property Investments Limited | Real estate | 2022 |
| Midco Care Limited | Health & social care | 2013 |
| Middle Farm Holdings Limited | Real estate | 2023 |
| Middleton Electrical Contractors Limited | Construction | 2019 |
| Midea Investments Limited | Other services | 2019 |
| Midenn Investment Properties LLP | | 2025 |