| Miller & Mckaig Limited | Hospitality | 1997 |
| Miller's Cafe Limited | Hospitality | 2019 |
| Millgate (Winchester) Limited | Construction | 2002 |
| Millington TEC Limited | Other services | 2017 |
| Millstream Films and Media Limited | Information & communication | 2014 |
| Milnthorpe Lane Residents Association Limited | Households | 1995 |
| Milvus Trade Ltd | Construction | 2021 |
| Mind Medicine Ltd | Health & social care | 2020 |
| Mindfizz Multimedia Limited | Information & communication | 2006 |
| Minds EYE Interactive Limited | Information & communication | 2002 |
| Minerva Cytology Services Limited | Health & social care | 2009 |
| Minis-R-Us Limited | Wholesale & retail | 2006 |
| Ministry of Fish Marketing Limited | Professional & scientific | 2005 |
| Mint Tea Boutique Limited | Wholesale & retail | 2011 |
| Mint Walk Management (Croydon) Limited | Households | 1998 |
| Miracle Engineering & Consultancy Limited | Professional & scientific | 2018 |
| Miracle Press Limited | Manufacturing | 2013 |
| Miracle Street UK | Arts & recreation | 2008 |
| Miss Illuminati Ltd | Administrative & support | 2025 |
| Mission in Land Limited | Real estate | 2024 |
| Mistral RE Investments Ltd | Real estate | 2022 |
| Mitchell Graham Design Limited | Professional & scientific | 2011 |
| Mixa Restaurants Ltd | Hospitality | 2026 |
| Mixez Limited | Professional & scientific | 1996 |
| Mixza Limited | Wholesale & retail | 2026 |
| Mizuki Ltd | Hospitality | 2020 |
| Mjal Limited | Hospitality | 2020 |
| MJC Design (Southern) Limited | Professional & scientific | 2017 |
| MJG Land Profits Limited | Real estate | 2025 |
| MJP Technical Services Limited | Information & communication | 2003 |
| MJS Steel & Glass Ltd | Construction | 2023 |
| MJW Bloodstock Ltd | Agriculture & fishing | 2026 |
| MKP Consultants Limited | Professional & scientific | 1999 |
| Mkpg Limited | Financial services | 2019 |
| MLS Builders Ltd | Construction | 2016 |
| MM Driveways & Landscaping Ltd | Administrative & support | 2025 |
| Mmmb Construction Ltd | Water & waste | 2023 |
| MN Accountants Limited | Professional & scientific | 2009 |
| MN Tax Accountants Limited | Professional & scientific | 2021 |
| MN Tax Consultants Limited | Professional & scientific | 2009 |
| Mobilise Therapy Ltd | Other services | 2025 |
| Modern Times Limited | Manufacturing | 1989 |
| Modnar Limited | Real estate | 2013 |
| Mojacu Ltd | Hospitality | 2017 |
| Molecular Medical Services Ltd | Health & social care | 2025 |
| Mollart CBT Ltd | Health & social care | 2019 |
| Molyneux Medico-Legal and Consulting Ltd | Health & social care | 2014 |
| Momentum Health Experience Limited | Professional & scientific | 2026 |
| Momentum Tennis Limited | Education | 2016 |
| Monarch Laundry Limited | Other services | 2017 |
| Mondo Rosso Ltd | Information & communication | 2004 |
| Monkey Bath Limited | Professional & scientific | 2007 |
| Monkey Puzzle Court Property Management Limited | Households | 2004 |
| Monmouth Square Residents Association Limited | Households | 1982 |
| Monopulse Limited | Information & communication | 2018 |
| Montilaw Ltd | Professional & scientific | 2020 |
| Moonrock Productions Ltd | Extraterritorial | 2022 |
| Moonsite Ltd | Wholesale & retail | 2016 |
| Moor Court Farms Limited | Agriculture & fishing | 1997 |
| Moores Veterinary Services Ltd | Professional & scientific | 2021 |
| Moorside Cafe Management Limited | Financial services | 2020 |
| Morbin Audio Limited | Manufacturing | 2014 |
| Morestead Associates Limited | Professional & scientific | 2022 |
| Morgan Consulting Services Limited | Professional & scientific | 2026 |
| Morgan Investment Property Ltd | Real estate | 2017 |
| Morgan Property Investments Ltd | Real estate | 2016 |
| Morgan Shepherd Ltd | Administrative & support | 2008 |
| Morleys Green Management Limited | Extraterritorial | 2014 |
| Morning Blossoms Ltd | Wholesale & retail | 2023 |
| Morning Start Transport Courier Ltd | Transport & logistics | 2026 |
| Morningside Group Profits Ltd | Real estate | 2024 |
| Mortimers Farm Limited | Agriculture & fishing | 1973 |
| Morton Kitchen Installations Limited | Construction | 2015 |
| Mosaic Maps Ltd | Information & communication | 2024 |
| Most Associates Limited | Professional & scientific | 2017 |
| Motherplant UK Limited | Wholesale & retail | 2025 |
| Moto Rapido Limited | Wholesale & retail | 2004 |
| Moto Rapido Racing Ltd | Wholesale & retail | 2008 |
| Mountain Coach Ltd | Administrative & support | 2025 |
| Mountbatten Court Management (Aldershot) Limited | Households | 1988 |
| Move Team South Coast Limited | Transport & logistics | 2024 |
| MOW2VATION Services Ltd | Professional & scientific | 2019 |
| MP Building Services (Oakley) Ltd | Construction | 2020 |
| Mpeguk Business Media Solutions Ltd | Administrative & support | 2026 |
| Mphl Consulting Limited | Professional & scientific | 2026 |
| MPL Markets Limited | Administrative & support | 2009 |
| Mpowerup Consulting Ltd | Information & communication | 2021 |
| MRJ Miller Limited | Construction | 2024 |
| Mrjc Property Limited | Real estate | 2024 |
| MS Secondment Ltd | Administrative & support | 2026 |
| Msec Engineering Limited | Professional & scientific | 2016 |
| Msjk Limited | Professional & scientific | 2011 |
| MSL 360 Ltd | Professional & scientific | 2020 |
| Msqrd Limited | Real estate | 2025 |
| MTC Capital Ltd | Real estate | 2017 |
| Mtec Scaffolding Services Ltd | Construction | 2008 |
| MTP Global Solutions Ltd | Wholesale & retail | 2011 |
| MTR Consulting Limited | Professional & scientific | 2026 |
| Muddl. Ltd | Manufacturing | 2026 |
| Mudeford Capital Limited | Financial services | 2023 |