| Mirror Hair Design Exeter Limited | Other services | 2021 |
| Mirt Building Maintenance Ltd | Construction | 2023 |
| Misc Ltd | Transport & logistics | 2019 |
| Mistry Connect Limited | Real estate | 2022 |
| Misura AI Ltd | Information & communication | 2025 |
| Mitchell Moss & Associates Ltd | Professional & scientific | 2011 |
| Mitchell Restaurants Limited | Hospitality | 2010 |
| Mitchell Rowe Services Limited | Manufacturing | 2017 |
| Mitobu Import Limited | Wholesale & retail | 2023 |
| Mitreburn Limited | Arts & recreation | 1996 |
| MIX Clean Green Ltd | Manufacturing | 2019 |
| MIX Tech Ltd | Wholesale & retail | 2015 |
| MJ 4PROPERTIES Limited | Real estate | 2017 |
| MJ Baker Surveyors Limited | Construction | 2024 |
| MJ Collections Ltd | Transport & logistics | 2012 |
| MJ Lake & Sons Limited | Construction | 2025 |
| MJC Europe Limited | Other services | 2015 |
| MJC Rotor Services Ltd | Transport & logistics | 2025 |
| MJE Industries Ltd | Professional & scientific | 2023 |
| MJH Accountancy (South West) Limited | Professional & scientific | 2012 |
| MJL Leisure Ltd | Other services | 2025 |
| MJM Architecture Ltd | Professional & scientific | 2021 |
| MJP Financial Planning Ltd | Professional & scientific | 2022 |
| MJS Planning & Design Limited | Professional & scientific | 2012 |
| MJS Properties (South West) Limited | Real estate | 2018 |
| MK 1 Limited | Construction | 1993 |
| MK Convenience Ltd | Wholesale & retail | 2023 |
| MKT Healthcare Limited | Health & social care | 2010 |
| ML Home Design Limited | Professional & scientific | 2008 |
| ML Whitchurch Holdings Ltd | Financial services | 2024 |
| Mlcp Ltd | Construction | 2024 |
| MLG Emporium Ltd | Wholesale & retail | 2025 |
| MLS Ophthalmology Limited | Health & social care | 2025 |
| MM Digital Marketing Limited | Information & communication | 2026 |
| MM Furness Property Management Ltd | Administrative & support | 2023 |
| MM Furness Waste Disposal Ltd | Wholesale & retail | 2023 |
| MMC Medical Limited | Manufacturing | 2020 |
| MMK Engineering Ltd | Manufacturing | 2015 |
| MNA Bricklaying Contractors Ltd | Construction | 2023 |
| MNC Contracting Ltd | Construction | 2018 |
| MNR Electrical Limited | Construction | 2023 |
| MNS Endodontics Limited | Health & social care | 2021 |
| MO Executive Taxis Limited | Transport & logistics | 2022 |
| Mobile Auto Electrical Services (Torquay) Ltd | Wholesale & retail | 2005 |
| Mobiloo CIC | Manufacturing | 2017 |
| Mocha (Taunton) Ltd | Real estate | 2022 |
| Moco Rentals Ltd | Information & communication | 2026 |
| Moda. Limited | Professional & scientific | 2003 |
| Modern RUM Co Ltd | Manufacturing | 2021 |
| Modern Stoicism | Education | 2017 |
| Moderncave Ltd | Wholesale & retail | 2025 |
| Moderninteriordesigns Ltd | Wholesale & retail | 2022 |
| Modification Nation Ltd | Wholesale & retail | 2026 |
| Moffitt Logistics Limited | Transport & logistics | 2021 |
| Moggers Limited | Real estate | 2018 |
| Mojo Automation Ltd | Administrative & support | 2017 |
| Moko Property Limited | Real estate | 2023 |
| Moksa Skincare Limited | Wholesale & retail | 2025 |
| Moktram Limited | Real estate | 2015 |
| Molart Limited | Real estate | 2010 |
| Molbrook Management Company Limited | Households | 2023 |
| Mold Product Design Ltd | Professional & scientific | 2018 |
| Molecular Research Limited | Professional & scientific | 2011 |
| Moles Cross Limited | Real estate | 2007 |
| Molly BEE Limited | Manufacturing | 2024 |
| Molly Holdings Ltd | Real estate | 2020 |
| Molten Wedding Ring Company Limited | Manufacturing | 2017 |
| Moment Chain Ltd | Wholesale & retail | 2025 |
| Moment Masters Ltd | Hospitality | 2026 |
| Momentum Enterprises Ltd | Wholesale & retail | 2025 |
| Monera Media Limited | Extraterritorial | 2023 |
| Money and Marriage Ltd | Professional & scientific | 2026 |
| Moneyhire Limited | Financial services | 2014 |
| Moneytest Holdings Ltd | Professional & scientific | 2024 |
| Moneytest Ltd | Professional & scientific | 2001 |
| Monkerton Court Management Company Limited | Households | 1997 |
| Monkton Court Limited | Extraterritorial | 2025 |
| Monkton Maintenance Management Limited | Real estate | 2022 |
| Monmouth Street Management Company Limited | Households | 1986 |
| Mono One Ltd | Professional & scientific | 2018 |
| Monopoly Partners Ltd | Construction | 2012 |
| Monroo Ltd | Wholesale & retail | 2021 |
| Mont Properties Limited | Real estate | 2021 |
| Montclair Three Limited | Real estate | 2021 |
| Monteros (UK) Limited | Professional & scientific | 2006 |
| Montgomery Energy Management Company Limited | Energy | 2011 |
| Montgomery Properties South West Limited | Real estate | 2019 |
| Monty's Devon Ltd | Wholesale & retail | 2009 |
| Moonbow Escapes Limited | Hospitality | 2012 |
| Moonlight Beauty 68 Ltd | Other services | 2024 |
| Moonlight Search Ltd | Administrative & support | 2019 |
| Moonshine Detailing Products Ltd | Wholesale & retail | 2020 |
| Moor Dental Care Limited | Health & social care | 2009 |
| Moor to Sea Ltd | Professional & scientific | 2026 |
| Moorhayes Court (Talaton) Management Company Limited | Households | 1989 |
| Moorhen Properties Limited | Real estate | 2020 |
| Moorlands (Whitby) Limited | Construction | 2009 |
| Moorlands Wildlife Centre CIC | Professional & scientific | 2024 |
| Moortown Limited | Construction | 2017 |
| Moorview Motors Limited | Wholesale & retail | 2024 |