| Moons Hill Administrative Services Limited | Health & social care | 1997 |
| Moonsault Projects Ltd | Information & communication | 2022 |
| Moonshine Location Catering Ltd | Hospitality | 2022 |
| Moontrail Ltd | Professional & scientific | 2026 |
| Moonvault TCG Limited | Wholesale & retail | 2026 |
| Moore's Motor Repairs Ltd | Wholesale & retail | 2001 |
| Moores (Fencing & Building Services) Limited | Construction | 2008 |
| Moores Motors Abercarn Ltd | Wholesale & retail | 2019 |
| Moorland Mayfair Wealth Management Limited | Financial services | 2015 |
| MOOSEYE786 Courier Ltd | Transport & logistics | 2019 |
| More Drylining Ltd | Construction | 2023 |
| More IW Holdings Limited | Real estate | 2019 |
| Morecom Ltd | Information & communication | 2008 |
| Moreland Heather Ltd | Real estate | 2022 |
| Moreli Food Ltd | Hospitality | 2024 |
| Moreton Park Barns Management Company Limited | Households | 2007 |
| Morf Designs Limited | Professional & scientific | 2007 |
| Morgan (Power Generation) Limited | Energy | 2009 |
| Morgan and Owen (Building Services) Limited | Wholesale & retail | 1976 |
| Morgan Business Solutions Ltd | Real estate | 2013 |
| Morgan Family Fish&Chips Ltd | Hospitality | 2025 |
| Morgan Garden Studios Limited | Professional & scientific | 2018 |
| Morgan Kinsey Ltd | Administrative & support | 2025 |
| Morgan Psychological Services Limited | Health & social care | 2002 |
| Morgans Family Partnership LLP | | 2022 |
| Morgans of USK Group Limited | Financial services | 2011 |
| Morgans of USK Limited | Manufacturing | 1987 |
| Morgans Property (IOW) Limited | Real estate | 2005 |
| Morgas Limited | Construction | 2006 |
| Morillion Consultancy Ltd | Professional & scientific | 2006 |
| Mornhill Limited | Agriculture & fishing | 2025 |
| Morpike Properties Limited | Real estate | 2023 |
| Morrello Health Limited | Administrative & support | 2009 |
| Morrello's Marvels Community Interest Company | Health & social care | 2020 |
| Morris & Buckley Properties Limited | Real estate | 1954 |
| Morrisoft Solutions Ltd | Information & communication | 2021 |
| Mortada Elemam Ltd | Transport & logistics | 2025 |
| Mortgage Advice Service Ltd | Financial services | 2003 |
| Mortgage Lane Limited | Financial services | 2018 |
| Mortgage Master Ltd | Administrative & support | 2023 |
| Mortgage Sure Ltd | Financial services | 2014 |
| Mortsgreb Ltd | Real estate | 2014 |
| Mosaic Portsmouth Limited | Hospitality | 2018 |
| Mose Rising Ltd | Financial services | 2022 |
| Moses & Walker Limited | Hospitality | 2019 |
| Moss Electrical Solutions Limited | Construction | 2025 |
| Motahub Limited | Wholesale & retail | 2019 |
| Motex Easiest Limited | Information & communication | 2000 |
| Motex Systems Limited | Information & communication | 1989 |
| Mother and Child Care Ltd | Health & social care | 2025 |
| Motherhood and ME CIC | Other services | 2026 |
| Motor Experts Limited | Wholesale & retail | 2026 |
| Motor Meet Ltd | Wholesale & retail | 2025 |
| Motor Plus South Wales Limited | Extraterritorial | 2012 |
| Motorhome Tours Limited | Administrative & support | 2013 |
| Motorpod Limited | Wholesale & retail | 2020 |
| Motorsports Marketing Ltd | Professional & scientific | 2025 |
| Motorspot Newport Ltd | Wholesale & retail | 2024 |
| Moulton Steel Limited | Manufacturing | 2023 |
| Mount Pleasant House Management Company Limited | Households | 1986 |
| Mount View Bath Ltd | Real estate | 2022 |
| Mountain Angel Films Limited | Professional & scientific | 2000 |
| Mountbatten Isle of Wight Limited | Health & social care | 1994 |
| Mountjoy Garages Ltd | Real estate | 2025 |
| Mountstuart Developments Limited | Construction | 1989 |
| Mouse Tech Limited | Other services | 2018 |
| Move to Where Ltd | Transport & logistics | 2025 |
| Moveonce Ltd | Professional & scientific | 2019 |
| Moving Art Ltd | Professional & scientific | 2023 |
| Mowbray House Easingwold Limited | Administrative & support | 1992 |
| Moytham Ltd | Health & social care | 2019 |
| MP & AE Burke Ltd | Professional & scientific | 2026 |
| MP Garden Construction Company Ltd | Construction | 2025 |
| MP Trading Management Ltd | Hospitality | 2025 |
| MPA Accounting Ltd | Professional & scientific | 2011 |
| MPC 2014 Limited | Professional & scientific | 2014 |
| MPH GAS Limited | Construction | 2009 |
| Mpkp Investments Ltd | Real estate | 2017 |
| MPM Civils Ltd | Construction | 2022 |
| Mpqi Consulting Ltd | Professional & scientific | 2024 |
| MR and MRS Clark Ltd | Arts & recreation | 2011 |
| MR Beautea Ltd | Other services | 2025 |
| MR Bubble Car Wash Ltd | Other services | 2025 |
| MR G'S Properties Ltd | Real estate | 2022 |
| MR Manufacture Ltd | Manufacturing | 2026 |
| MR Monkeys Emporium Ltd | Wholesale & retail | 2015 |
| MR Morris Plastering Ltd | Construction | 2024 |
| MR November Productions Ltd | Information & communication | 2024 |
| MR. Sprinkles' Munchies Ltd | Manufacturing | 2024 |
| Mrbms Ltd | Professional & scientific | 2012 |
| MRF Cleaning Services Ltd | Administrative & support | 2021 |
| MRF Commercial Cleaning Services Ltd | Administrative & support | 2023 |
| Mrrails.Com Limited | Manufacturing | 2013 |
| MS Newport Ltd | Administrative & support | 2021 |
| MS46 Enterprise Ltd | Wholesale & retail | 2026 |
| Mscorpuz Limited | Real estate | 2025 |
| MSF Developments Limited | Construction | 2012 |
| Msfl Properties Ltd | Real estate | 2018 |
| MSH Engineering Ltd | Professional & scientific | 2026 |
| MSJ Events Limited | Administrative & support | 2011 |