| Mangwanda Tradings Limited | Health & social care | 2010 |
| Mani Recruitment Agency Ltd | Health & social care | 2026 |
| Manicaland PVT Ltd | Transport & logistics | 2024 |
| Manley Drainage Ltd | Construction | 2007 |
| Manmun UK Ltd | Wholesale & retail | 2011 |
| Mann Investor Ltd | Real estate | 2025 |
| Manna Pro UK Limited | Wholesale & retail | 2019 |
| Manny Autos Ltd | Wholesale & retail | 2026 |
| Mano Pack Limited | Manufacturing | 2017 |
| Manor Bridge (Trading) Ltd | Households | 2025 |
| Manor Court (Warmington) Management Company Limited | Households | 2018 |
| Manor Estates (Sibson) Limited | Agriculture & fishing | 1973 |
| Manor Estates Construction Ltd | Construction | 2023 |
| Manor Farm Chesterton Management Company Limited | Real estate | 2020 |
| Manor Farm Court (Haddon) Management Company Limited | Households | 2008 |
| Manor Group Services Ltd | Real estate | 2024 |
| Manor House Nursery (Peterborough) Limited | Education | 2011 |
| Manor Packaging Limited | Manufacturing | 1987 |
| Manor Roofing Repair Limited | Construction | 2024 |
| Manos Amigas + LLP | | 2025 |
| Mansfield Smile Centre Ltd | Health & social care | 2025 |
| Mansfield Snooker Club Ltd | Other services | 2005 |
| Mantas Trans Ltd | Transport & logistics | 2017 |
| Manthorpe Chase Management Company Limited | Households | 2024 |
| Manthorpe Slate and Stone Ltd. | Manufacturing | 2009 |
| Mantis Innovation Ltd | Professional & scientific | 2021 |
| Mantis Security Organisation Ltd | Extraterritorial | 2021 |
| Manual Handling Solutions Limited | Wholesale & retail | 2010 |
| Mapa Sporting Limited | Construction | 2024 |
| Maple & Moon Studio Limited | Other services | 2024 |
| Maple Development Services Limited | Real estate | 2021 |
| Maplenest Ltd | Real estate | 2025 |
| Maplumb Plumbing & Heating Services Limited | Construction | 2020 |
| MAQ Property Group Ltd | Real estate | 2026 |
| Maqam Ltd | Real estate | 2025 |
| Maqnet AI Limited | Information & communication | 2025 |
| Mar-Tom Ltd | Transport & logistics | 2024 |
| Marabeas Alley Digitally Limited | Wholesale & retail | 2025 |
| Marayika Transport Limited | Transport & logistics | 2020 |
| Marbeno Ltd | Transport & logistics | 2024 |
| Marblestone Digital Limited | Extraterritorial | 2024 |
| Marc Innovative Energy Limited | Construction | 2025 |
| Marcel a. Wilson Wealth Management Ltd | Administrative & support | 2005 |
| Marceybenard Consultancy Limited | Professional & scientific | 2021 |
| March Armed Forces and Veterans Hub C.I.C. | Information & communication | 2022 |
| March Convenience Store T/As Family Shopper Ltd | Wholesale & retail | 2015 |
| March Convenience Store T/As the Corner Shop Ltd | Wholesale & retail | 2013 |
| March Kebabs & Pizza Limited | Hospitality | 2018 |
| Marchexia Limited | Information & communication | 2014 |
| Marchiori's Ltd | Transport & logistics | 2024 |
| Marchwood (Africa Drive) Residents Company Limited | Households | 2012 |
| Marchwood Residents Company Limited | Households | 2006 |
| Marcius Ltd | Transport & logistics | 2016 |
| Marclin Limited | Administrative & support | 2017 |
| Marco BS Ltd | Other services | 2025 |
| Marco Castelli Ltd | Extraterritorial | 2018 |
| Marco Construction Limited | Extraterritorial | 1979 |
| Marco Izzo Hairdressing Limited | Other services | 2011 |
| Marco West Enterprise Limited | Administrative & support | 2019 |
| Marco West Group Ltd | Construction | 2023 |
| Marco West Homes Limited | Administrative & support | 2023 |
| Marcupam Services Ltd | Transport & logistics | 2014 |
| Mareco Ltd | Wholesale & retail | 2018 |
| Marek Kurowski Transport Ltd | Transport & logistics | 2026 |
| Marflo Trans Limited | Transport & logistics | 2014 |
| Margaret Rose Design Ltd | Professional & scientific | 2021 |
| Margaret Telfer Limited | Health & social care | 2019 |
| Margo Ltd | Transport & logistics | 2020 |
| Margol Ltd | Transport & logistics | 2023 |
| Marham Residents Company Limited | Households | 2010 |
| Marholm Court Management Limited | Households | 1991 |
| Maria&Domi Trans Ltd | Transport & logistics | 2019 |
| Maria&Rapha Limited | Transport & logistics | 2023 |
| Mariam Ladies Fitness Limited | Arts & recreation | 2026 |
| Marian 69 Ltd | Transport & logistics | 2019 |
| Marian Amitrului Limited | Administrative & support | 2014 |
| Marian Transportation Ltd | Transport & logistics | 2025 |
| Marian Verman Limited | Transport & logistics | 2015 |
| Maribel Peterborough Ltd | Other services | 2016 |
| Marigold ENG Ltd | Wholesale & retail | 2025 |
| Marijah Properties Limited | Real estate | 2022 |
| Marina View (Wansford) Limited | Construction | 2015 |
| Marine & Structural Engineering Ltd | Construction | 2006 |
| Marino's Ironing Limited | Administrative & support | 2020 |
| Mario Renda Ltd | Health & social care | 2024 |
| MARIO24 Ltd | Wholesale & retail | 2025 |
| Marioandreitr Ltd | Construction | 2021 |
| Marios Antoniou Limited | Health & social care | 2015 |
| Mariovali Limited | Transport & logistics | 2024 |
| Marisan Limited | Hospitality | 2011 |
| Maritime Freight Ltd | Transport & logistics | 2025 |
| Maritime Sphere Solutions Ltd | Transport & logistics | 2025 |
| Marius Enaken Ltd | Transport & logistics | 2025 |
| Marius Motors Ltd | Wholesale & retail | 2025 |
| Marius Mustafa Driver Ltd | Transport & logistics | 2025 |
| Marius Security Co Ltd | Administrative & support | 2025 |
| Mark Abraham GAS, OIL & LPG Boiler Services Ltd | Construction | 2012 |
| Mark Abraham Holdings Limited | Financial services | 2025 |
| Mark Ford Electrical Limited | Administrative & support | 2003 |
| Mark Hall Sales Agent Ltd | Wholesale & retail | 2023 |