| Midwest Marketing Limited | Wholesale & retail | 1994 |
| MIE Cctv Limited | Information & communication | 2011 |
| Mighty Vape Limited | Wholesale & retail | 2015 |
| Migliore Cars Limited | Wholesale & retail | 2007 |
| Migreats Ltd | Information & communication | 2023 |
| Mike Foster Fitness Ltd | Arts & recreation | 2022 |
| Mike Mckinley Lettings Ltd | Real estate | 2024 |
| MIL Consulting Limited | Professional & scientific | 2018 |
| Miles Industries Property Holdings Limited | Professional & scientific | 1989 |
| Miles Partitioning Industries Limited | Construction | 1983 |
| Miles Property Limited | Real estate | 1988 |
| Miles William Building UK Limited | Construction | 2026 |
| Mili&Jim Ltd | Arts & recreation | 2022 |
| Milldale Consultants Limited | Professional & scientific | 2024 |
| Millers Green (Shelfield Drive) Management Company Limited | Households | 2003 |
| Millfield Residential Surveying Ltd | Professional & scientific | 2026 |
| Millpool Stone Ltd | Manufacturing | 2018 |
| Millside Court Residents Limited | Households | 1999 |
| Millstok Ltd | Wholesale & retail | 2022 |
| Millstone Partners Limited | Professional & scientific | 2005 |
| Mimy's Salon Ltd | Other services | 2025 |
| Mina Carter Limited | Information & communication | 2012 |
| Mind Cafe Trading Ltd | Professional & scientific | 2025 |
| Mindless Group Ltd | Information & communication | 2023 |
| Mineham Mortgage Services Limited | Information & communication | 2015 |
| Minerva Communications Limited | Construction | 1989 |
| Minerva Services Limited | Professional & scientific | 2020 |
| Mini Swimmers Swim Ltd | Arts & recreation | 2015 |
| Miniature Model Depot Ltd | Manufacturing | 2025 |
| Minos Bromsgrove Limited | Hospitality | 2018 |
| Minster Distribution Ltd | Wholesale & retail | 1998 |
| Minted Cleaning Services Ltd | Administrative & support | 2023 |
| Mirella Consulting Limited | Information & communication | 2021 |
| Mission Create Ltd | Manufacturing | 2021 |
| Mission Interior Contracts Limited | Construction | 1996 |
| Mission Neon Ltd | Manufacturing | 2023 |
| MIU MIU Midlands Ltd | Hospitality | 2023 |
| Mizara Digicom Limited | Wholesale & retail | 2025 |
| MJA 4 X 4 Limited | Wholesale & retail | 2008 |
| MJC Engineering Services Limited | Manufacturing | 2025 |
| MJH Vehicle Services Limited | Wholesale & retail | 2006 |
| MJS IT Services Ltd | Information & communication | 2003 |
| MJS Technical Solutions Limited | Information & communication | 2015 |
| Mloc Ltd | Other services | 2012 |
| MLP Events Limited | Arts & recreation | 2016 |
| MLR Installations Ltd | Construction | 2025 |
| MLR Management Ltd | Construction | 2024 |
| MMF Health Limited | Health & social care | 2022 |
| MMR Legal Limited | Professional & scientific | 2017 |
| Moat Farm House Properties LLP | | 2010 |
| Mobhut Bletchley Ltd | Wholesale & retail | 2023 |
| Modern Convict Films Limited | Arts & recreation | 2018 |
| Modern Lighting and Electrical Ltd | Construction | 2023 |
| Mondo Productions Ltd | Administrative & support | 2013 |
| Monkey Puzzle Developments Limited | Construction | 2018 |
| Monza 1922 Holdings Limited | Extraterritorial | 2017 |
| Mooch Creative Limited | Information & communication | 2002 |
| Mooody COW Limited | Information & communication | 2015 |
| Moore Insight Limited | Professional & scientific | 2025 |
| Moorhen Limited | Financial services | 2018 |
| Moors Farm Management Company Limited | Households | 1989 |
| Moose Junction Limited | Extraterritorial | 2008 |
| Moreton & SON Ltd | Construction | 2015 |
| Moreton Human Intelligence Ltd | Professional & scientific | 2026 |
| Morgan Day Properties Ltd | Real estate | 2022 |
| Morgan Evans Therapeutic Services Ltd | Professional & scientific | 2023 |
| Morgan Vent Systems Ltd | Construction | 2021 |
| Morgans Catering for YOU Limited | Hospitality | 2013 |
| Morris Farrier Supplies Ltd | Professional & scientific | 2026 |
| Mortgage Brain Holdings Limited | Information & communication | 1999 |
| Mortgage Brain Limited | Information & communication | 1986 |
| Mortgage RE Mortgage Limited | Financial services | 2003 |
| Mortgagestream Limited | Extraterritorial | 2002 |
| Moseley Washeteria Ltd | Other services | 2023 |
| Motorholics Clothing Ltd | Manufacturing | 2016 |
| Moulding Technology International Ltd | Extraterritorial | 2024 |
| Mounts Street Ltd | Construction | 2024 |
| Move MEN Services Ltd | Water & waste | 2025 |
| Moxon Group Limited | Financial services | 2022 |
| MPC Supply Chain Solutions Ltd | Professional & scientific | 2024 |
| Mpcs Studios Ltd | Information & communication | 2024 |
| MPS Accountancy Ltd | Professional & scientific | 2024 |
| MPS Hold Co Ltd | Financial services | 2024 |
| MR and MRS Wheatley Limited | Information & communication | 2002 |
| MR Mahar Ltd | Wholesale & retail | 2024 |
| MRK Chefs Limited | Administrative & support | 2023 |
| Mrsmummyboss Ltd | Professional & scientific | 2021 |
| MS Consulting & Research Limited | Administrative & support | 2003 |
| MS I.T. Repairs Ltd | Other services | 2017 |
| MSB Investments Ltd | Extraterritorial | 2022 |
| MSH Investments Ltd | Real estate | 2019 |
| MSH Real Estate Limited | Real estate | 2017 |
| MT House Holdings Ltd | Real estate | 2019 |
| MTC Properties Midlands Ltd | Financial services | 2025 |
| MTD Group Limited | Financial services | 2025 |
| Mulai Ltd | Manufacturing | 2024 |
| Mulberry Independent Financial Advisers Limited | Financial services | 2006 |
| Multigate Medical Products UK Limited | Manufacturing | 2019 |
| Multiplication Limited | Financial services | 2007 |
| Muntjactrading Ltd | Agriculture & fishing | 2008 |