| Micro Support Limited | Information & communication | 2016 |
| Microscopes South West Limited | Wholesale & retail | 2011 |
| Midex Automotive Ltd | Professional & scientific | 2024 |
| Midnight Foxes Consultancy Ltd | Manufacturing | 2021 |
| MIE Properties (SW) Ltd | Real estate | 2024 |
| Miedja Limited | Financial services | 2014 |
| MIK72 Ltd | Hospitality | 2025 |
| Mike Anderson Plumbing Ltd | Construction | 2022 |
| Mike Whittaker Carpentry & Building Contractors Ltd | Construction | 2014 |
| Mikethemagicman Ltd | Wholesale & retail | 2025 |
| Mila Property Investments Ltd | Real estate | 2024 |
| Milbury Gardens Management Company Limited | Real estate | 2017 |
| Milforce Group Ltd | Construction | 2025 |
| Milk Thistle Bars Ltd | Hospitality | 2018 |
| Millbay Property Investments Ltd | Real estate | 2019 |
| Millichap Ltd | Real estate | 2021 |
| Millioncare Ltd | Health & social care | 2014 |
| Milsom Ltd | Administrative & support | 2017 |
| Milton Auto Services Limited | Wholesale & retail | 2009 |
| Milton Property Services Limited | Real estate | 2020 |
| Mimi’S Thai Ltd | Hospitality | 2023 |
| Mind Coaching Limited | Education | 2020 |
| Mindbase Limited | Health & social care | 2023 |
| Minotaur Software Limited | Information & communication | 2011 |
| Mint and Lime Limited | Information & communication | 2010 |
| MINT2PINK Limited | Extraterritorial | 2019 |
| Minty Design Limited | Administrative & support | 2007 |
| Mira Foods Limited | Hospitality | 2019 |
| Miracle 1962 Limited | Administrative & support | 2014 |
| Miracle Rain Ltd | Health & social care | 2019 |
| Mirage (Port Marine) Management Company Limited | Households | 2007 |
| Mirage Interiors Limited | Construction | 1998 |
| Miralo Education Group Ltd | Education | 2024 |
| Missed Limited | Real estate | 2024 |
| Missenden & Mccoy Limited | Professional & scientific | 1998 |
| Mitre Construction S.W Ltd | Construction | 2025 |
| MIX Store Ltd | Wholesale & retail | 2018 |
| MJ Living Ltd | Hospitality | 2023 |
| MJ Management Solutions Ltd | Professional & scientific | 2018 |
| MJC Plumbing and Heating Diagnostics Ltd | Professional & scientific | 2025 |
| MJG Design Services Ltd | Professional & scientific | 2018 |
| MJJ Traders Limited | Wholesale & retail | 2023 |
| MJL Continental Limited | Transport & logistics | 2014 |
| Mjpls Ltd | Construction | 2025 |
| MJS Property Services Ltd | Construction | 2019 |
| MJV Improvements Ltd | Construction | 2022 |
| MK Building Services Ltd | Construction | 2023 |
| MKW Accounting Limited | Professional & scientific | 2018 |
| MMA Curier Ltd | Transport & logistics | 2025 |
| Mmia Holdings Limited | Financial services | 2025 |
| Mmia Newco Limited | Financial services | 2025 |
| MMS (SW) Ltd | Construction | 2022 |
| MNF Prod Ltd | Information & communication | 2021 |
| Mobile Plant Training Limited | Health & social care | 2008 |
| Mobile Timber Store.Com Ltd | Wholesale & retail | 2021 |
| Mobile Tyre Professionals Limited | Wholesale & retail | 2012 |
| Mocca SW Ltd | Wholesale & retail | 2015 |
| Moco New Home Consultants Limited | Real estate | 2023 |
| Moda Boutique (WSM) Limited | Wholesale & retail | 2016 |
| Mode Consult Ltd | Construction | 2019 |
| Modus Construction Services Ltd | Construction | 2023 |
| MOL Technical Services Limited | Professional & scientific | 2022 |
| Mondo Media Limited | Information & communication | 2013 |
| Monkton Heathfield Management Company Limited | Administrative & support | 2012 |
| Monopoly Property Services Limited | Real estate | 2022 |
| Mookraj Ltd | Hospitality | 2025 |
| Moore Property Law Limited | Professional & scientific | 2023 |
| Moores Heating Limited | Construction | 2018 |
| Moorhouse Property Investments Limited | Construction | 2001 |
| Moorland Carpets Limited | Construction | 2003 |
| Moorside Energy Reserve Limited | Construction | 2020 |
| Morani Limited | Professional & scientific | 2013 |
| Morgan Armstrong Limited | Administrative & support | 2018 |
| Morgan Bishop Limited | Professional & scientific | 1998 |
| Morgan Mortgages Limited | Financial services | 2017 |
| Morris Brickwork Limited | Construction | 2024 |
| Morris Fryers Ltd | Hospitality | 2014 |
| Morse Windows Ltd | Construction | 2010 |
| Mortgage FOX Ltd | Financial services | 2023 |
| Mortgage Mind Financial Solutions Ltd | Professional & scientific | 2020 |
| Mortgage Mind Legacy Planning Ltd | Professional & scientific | 2025 |
| Moshfit Ltd | Information & communication | 2026 |
| Moss Motor Movements Ltd | Wholesale & retail | 2021 |
| Motor Bodies Weston Limited | Wholesale & retail | 2010 |
| Motor Swift Ltd | Wholesale & retail | 2019 |
| Motorart Ltd | Wholesale & retail | 2024 |
| Motormend Limited | Wholesale & retail | 2017 |
| Movecraft Services Ltd | Transport & logistics | 2026 |
| Movement & Wellbeing Ltd | Health & social care | 2014 |
| Mowtrac Limited | Wholesale & retail | 2019 |
| Mozaic Communications Ltd | Professional & scientific | 2015 |
| MP Electrical (SW) Limited | Construction | 2016 |
| MP24 Ltd | Real estate | 2024 |
| Mpdm Properties Ltd | Real estate | 2025 |
| MR Barry Services Security Limited | Administrative & support | 2023 |
| MR Fencer Ltd | Administrative & support | 2014 |
| MR Greek Ltd | Extraterritorial | 2020 |
| Mr&Jt Catering Ltd | Hospitality | 2023 |
| Mrgj Ltd | Administrative & support | 2017 |
| MS Beans Limited | Hospitality | 2024 |