| Milsteda Systems Limited | Information & communication | 2000 |
| Milston Ltd | Wholesale & retail | 2020 |
| MINCS20001 Limited | Financial services | 2023 |
| MINCS5001 Limited | Financial services | 2023 |
| Minda Traders Ltd | Construction | 2026 |
| Minesweeper GP Limited | Financial services | 2022 |
| MINJCW01 Limited | Arts & recreation | 2021 |
| Minmax Trading Limited | Wholesale & retail | 2026 |
| Minster Trust for Education | Education | 2018 |
| Mira&Mira Ltd | Wholesale & retail | 2025 |
| Mirrortrain Ltd | Professional & scientific | 2023 |
| Mishco Music Limited | Information & communication | 1999 |
| Misson Organic Dairying Limited | Agriculture & fishing | 2016 |
| Mitchell Collective Ltd | Professional & scientific | 2026 |
| Mitre Shop Fitting Ltd | Manufacturing | 2026 |
| Mixologist (London) Limited | Wholesale & retail | 2023 |
| Mizoola Ltd. | Professional & scientific | 2014 |
| MJ Retail Group Limited | Wholesale & retail | 2024 |
| MJK P-Way Engineering Limited | Construction | 2007 |
| MJM Hair Design Limited | Other services | 2001 |
| Mkab Group Ltd | Wholesale & retail | 2023 |
| ML Furniture Ltd | Wholesale & retail | 2025 |
| ML3 Ltd | Real estate | 2013 |
| ML4 (Notts) Ltd | Construction | 2022 |
| MLB Engineering Services (1994) Ltd | Manufacturing | 2012 |
| MLF Property Investments Limited | Real estate | 2022 |
| MMA Industrial Ltd | Construction | 2024 |
| Mobile Auto Tuning Ltd | Wholesale & retail | 2020 |
| Mobile Surface Preparation Ltd | Manufacturing | 2020 |
| Mollart Property Investments Ltd | Real estate | 2021 |
| Molly Barker Eventing Limited | Education | 2024 |
| Mondrelog Engineering Limited | Manufacturing | 2024 |
| Mondrelog Ltd | Manufacturing | 2021 |
| Mono Lighting Limited | Manufacturing | 2016 |
| Monster CBD Ltd | Wholesale & retail | 2019 |
| Mont BAS Ltd | Information & communication | 2025 |
| Montgomerie Farms Limited | Agriculture & fishing | 1965 |
| Montgomery Utilities Ltd | Construction | 2026 |
| Monument Financial Planning Limited | Financial services | 2016 |
| Moon & Back Properties Ltd | Real estate | 2024 |
| Moran Services Limited | Professional & scientific | 1999 |
| Moravia Management Company Limited | Households | 2005 |
| Morco Limited | Wholesale & retail | 1989 |
| More Than Just Beer Ltd | Hospitality | 2025 |
| Mori LEE Europe Limited | Wholesale & retail | 1999 |
| Morley Business Solutions Ltd | Professional & scientific | 2022 |
| Morley Gardens Management Company Limited | Households | 2012 |
| Morley Scales & Co Ltd | Wholesale & retail | 2024 |
| Morrell Corporate Estate Company Limited | Extraterritorial | 2015 |
| Morrell Family Estate Company Limited | Extraterritorial | 2015 |
| Mosa Boutique Ltd | Wholesale & retail | 2021 |
| Motive What’S Yours Ltd | Extraterritorial | 2024 |
| Moto Legends Distribution Limited | Wholesale & retail | 2008 |
| Motorcycle Investment Services Ltd | Wholesale & retail | 2018 |
| Motorfinity Group Limited | Wholesale & retail | 2017 |
| Motorfinity Leasing Limited | Extraterritorial | 2021 |
| MOVE2B Limited | Real estate | 2009 |
| Mowtivated Garden Care Ltd | Administrative & support | 2026 |
| Moxton Education Ltd | Education | 2014 |
| MP Mobile Valeting Ltd | Other services | 2019 |
| MPC Developments Limited | Households | 2008 |
| MR BS Brick and Block Ltd | Transport & logistics | 2024 |
| MR Chips 180 Limited | Hospitality | 2025 |
| MR Fixer Handyman Ltd | Construction | 2025 |
| MR Nice Removals Ltd | Transport & logistics | 2021 |
| MR Pattison Limited | Extraterritorial | 2014 |
| Mrbarlow Limited | Professional & scientific | 2016 |
| MRD Services Limited | Construction | 2015 |
| MRS Geldard's Limited | Wholesale & retail | 2026 |
| MS Holland Ltd | Households | 2025 |
| MS Nickless Limited | Construction | 2019 |
| MSM Express Ltd | Wholesale & retail | 2021 |
| Much More Than Beancounting Ltd | Professional & scientific | 2019 |
| Much More Than Letting Ltd | Real estate | 2026 |
| Mudpig Ltd | Wholesale & retail | 2025 |
| Mulliss Ltd | Real estate | 2024 |
| Munro Ventures Limited | Manufacturing | 2009 |
| Munson Transport (Holdings) Limited | Real estate | 2020 |
| Munson Transport Limited | Transport & logistics | 2002 |
| MUS Investments Ltd | Real estate | 2021 |
| Musabol Ventures Limited | Health & social care | 2017 |
| Musee Home Limited | Wholesale & retail | 2021 |
| Musgrove and Ball Limited | Professional & scientific | 2022 |
| Music 18 Ltd | Education | 2014 |
| Muskham OUT of School Club Ltd | Health & social care | 2007 |
| Muskna Ltd | Information & communication | 2024 |
| Mustard Software Ltd | Administrative & support | 2016 |
| Musto Energy Ltd | Professional & scientific | 2010 |
| Muur Interior Design and Build Ltd | Construction | 2025 |
| MV X Ltd | Construction | 2026 |
| MVH Farming Company | Agriculture & fishing | 2011 |
| MVL Transport Ltd | Transport & logistics | 2016 |
| MW Brickwork and Construction (Newark) Limited | Construction | 2019 |
| MW Transport Training Ltd | Education | 2025 |
| My Gym Space Ltd | Other services | 2013 |
| My Pace Resources Ltd | Education | 2026 |
| Myranea Ltd | Manufacturing | 2020 |
| Mytill Limited | Extraterritorial | 2016 |
| N & L Franklin Developments Limited | Construction | 2007 |
| N C Warren Site Management and Safety Services Limited | Construction | 2018 |