| MLC Roofing & Construction Ltd | Construction | 2025 |
| MLL Re-Sources Limited | Construction | 2010 |
| MLP Plastering Ltd | Construction | 2026 |
| MMN Barber Ltd | Other services | 2025 |
| MMO Audit Services Limited | Professional & scientific | 2024 |
| MN Windows and Doors Limited | Extraterritorial | 2013 |
| MOBBIN92 Music Publishing Limited | Information & communication | 2025 |
| Mobileweld Limited | Other services | 2014 |
| Mode House Ltd | Wholesale & retail | 2026 |
| Modern Build Holding Ltd | Financial services | 2024 |
| Modern Building Lets Ltd | Real estate | 2024 |
| Modern Commercial Interiors Ltd | Construction | 2007 |
| Modernise My Conservatory Limited | Construction | 2022 |
| Modina Property Ltd | Construction | 2020 |
| Moey Construction Ltd | Water & waste | 2014 |
| Mofex Cleaners Limited | Administrative & support | 2019 |
| MOH Meals Diner Limited | Hospitality | 2025 |
| Mojorisin Limited | Information & communication | 2022 |
| Mojou Limited | Information & communication | 2015 |
| Molly's K9 Pals Ltd | Agriculture & fishing | 2021 |
| Molrec Limited | Transport & logistics | 2025 |
| Mombie Ltd | Arts & recreation | 2026 |
| Monckton Holdings Ltd | Financial services | 2024 |
| Mondeep Limited | Wholesale & retail | 2025 |
| Mondo Film Limited | Information & communication | 2014 |
| Monelise Music Limited | Arts & recreation | 2019 |
| Monix Associates Limited | Administrative & support | 2023 |
| Monologue Records Limited | Professional & scientific | 2008 |
| Monsters 1NC Ltd | Real estate | 2025 |
| Montis Care Limited | Health & social care | 2017 |
| Moody Bird Southsea Ltd | Hospitality | 2026 |
| Moondance Services Limited | Professional & scientific | 2023 |
| Moonlightsgroup Limited | Financial services | 2025 |
| Moonrise Animation Studios Ltd | Information & communication | 2024 |
| Moonstick Limited | Administrative & support | 2023 |
| Moore & Co UK Limited | Construction | 2020 |
| Moore Estates (UK) Limited | Other services | 2013 |
| Moore Housing Solutions Ltd | Real estate | 2022 |
| Moore Property Rentals Limited | Real estate | 2024 |
| Moore Works Limited | Professional & scientific | 2003 |
| Moose Technologies Ltd | Information & communication | 2024 |
| Morburne Engineering Limited | Wholesale & retail | 2016 |
| More Car Sales Limited | Wholesale & retail | 2014 |
| More Lettings Limited | Real estate | 2021 |
| Morgan Finance Limited | Professional & scientific | 2026 |
| Morgan Shaw Limited | Construction | 2017 |
| Morganling Properties Limited | Real estate | 2022 |
| Moriah Defence Advisory Limited | Professional & scientific | 2026 |
| Moritz and Sloane Limited | Information & communication | 2022 |
| Morphec Consultancy Limited | Professional & scientific | 2017 |
| Morpheus Estates Limited | Real estate | 2018 |
| Morrison's Mobile Smart Repair Ltd | Manufacturing | 2023 |
| Mortgage Oasis Limited | Financial services | 2016 |
| Mortimer Carpentry Services Limited | Manufacturing | 2020 |
| Mosaic Automation Limited | Information & communication | 2025 |
| Mosaic Pharma Limited | Professional & scientific | 2022 |
| MOT Your Motor Limited | Wholesale & retail | 2025 |
| Motapart Wholesale Limited | Wholesale & retail | 2003 |
| Moth & Sons Ltd | Real estate | 2018 |
| Mother Tuckers Mobile Catering Ltd | Hospitality | 2022 |
| Motocover Ltd | Financial services | 2020 |
| Motorculture Limited | Manufacturing | 2002 |
| Mouldcast Limited | Wholesale & retail | 2019 |
| Moulds (Builders) Limited | Construction | 2008 |
| Moulhi Group Limited | Manufacturing | 2020 |
| Mount Noire Ltd | Administrative & support | 2020 |
| Mountain ASH Construction Ltd | Construction | 2026 |
| Mourne Concepts Limited | Real estate | 2004 |
| Movement Construction Ltd | Construction | 2023 |
| Movil Property International Ltd | Real estate | 2018 |
| Moving Made Easy Limited | Transport & logistics | 2016 |
| Moving Properties Limited | Professional & scientific | 2011 |
| Mower Services Limited | Manufacturing | 2022 |
| Mowlo Silk Limited | Information & communication | 2024 |
| MP Builder+Construction Ltd | Construction | 2025 |
| MPD Property Maintenance 13 Ltd | Construction | 2025 |
| Mpep Ltd | Professional & scientific | 2021 |
| MPL CNC Training Consultancy Limited | Professional & scientific | 2023 |
| MR Bubble Drink Limited | Hospitality | 2013 |
| MR Paul Garwood Limited | Information & communication | 2021 |
| MR Services South East Limited | Construction | 2021 |
| MRE Electrical Contractors Ltd | Construction | 2026 |
| Mrkl Fabrications Ltd | Construction | 2017 |
| MRL Group (South) Limited | Construction | 2013 |
| Mrlb Medical Services Limited | Health & social care | 2022 |
| MRS Plant Services Limited | Construction | 2016 |
| MS1 Ltd | Construction | 2018 |
| MS4I Ltd | Professional & scientific | 2025 |
| MSB Resurfacing Ltd | Construction | 2024 |
| Msblk Consultancy Limited | Professional & scientific | 2024 |
| Msdevan Ltd | Real estate | 2025 |
| MSJ Estates Ltd | Real estate | 2022 |
| MSL Consulting Limited | Professional & scientific | 1998 |
| MSN Consultants Ltd | Administrative & support | 2016 |
| MSN IT Ltd | Information & communication | 2020 |
| MT Riders Club Limited | Other services | 2018 |
| Mtech Southern Solutions Limited | Manufacturing | 2020 |
| MTL Electrical Ltd | Construction | 2021 |
| MTL Investment Group Ltd | Financial services | 2026 |
| MTL Properties South Ltd | Real estate | 2022 |