| Mobile Telecom Solutions Ltd | Wholesale & retail | 2025 |
| Mobilitas Group Limited | Financial services | 2017 |
| Model of Excellence Ltd | Education | 2017 |
| Mojmag Limited | Health & social care | 2012 |
| Moldofood Ltd | Hospitality | 2026 |
| Mondsey Limited | Professional & scientific | 2019 |
| Monex School of Motoring Limited | Education | 2011 |
| Monkeys USE Tools TOO Limited | Professional & scientific | 2025 |
| Monos A1 Healthcare Limited | Administrative & support | 2018 |
| Monrey Films Limited | Other services | 2018 |
| Montrose Consulting Ltd | Professional & scientific | 2024 |
| MOO Moo's Consultancy Limited | Administrative & support | 2012 |
| Moody Goose Brewery Limited | Manufacturing | 2014 |
| Moonlight Engineering Limited | Manufacturing | 2010 |
| Moonlite Accounts Ltd | Professional & scientific | 2018 |
| Moonsuit Ltd | Manufacturing | 2024 |
| Mordonal Limited | Real estate | 2017 |
| More Orange Limited | Extraterritorial | 2018 |
| Morgan and Preece Estates Ltd | Construction | 2021 |
| Morgap Limited | Real estate | 2024 |
| Morntidaa Siam Limited | Hospitality | 2018 |
| Morpheos Ltd | Information & communication | 2026 |
| Morris Estates (Essex) Limited | Administrative & support | 2017 |
| Mortgage Extra Ltd | Financial services | 2023 |
| Mortgage Matt Financial Services Limited | Financial services | 2023 |
| Mortier & Sons Limited | Construction | 2014 |
| Moscuzza Research Limited | Professional & scientific | 2016 |
| Moss Environmental Limited | Professional & scientific | 2026 |
| Motion Healthcare Limited | Wholesale & retail | 2015 |
| Motor Parts Direct (Holdings) Limited | Financial services | 2022 |
| Motor Parts Direct Limited | Wholesale & retail | 1998 |
| Motormatics Ltd | Wholesale & retail | 2021 |
| Motorvation 2000 Limited | Wholesale & retail | 2003 |
| Mower Hair Limited | Other services | 2020 |
| Mozeris Fine Antiques Limited | Wholesale & retail | 2015 |
| Mpgz Ltd | Professional & scientific | 2015 |
| MR Barbers Cambridge Limited | Other services | 2016 |
| MR Jolly CAB Limited | Extraterritorial | 2026 |
| MR Porter Brickwork Limited | Construction | 2018 |
| MRB Electrical Services Limited | Construction | 1998 |
| MRD Landscapes Limited | Administrative & support | 2026 |
| Mrpaas Limited | Information & communication | 2019 |
| MRT Services Ltd | Information & communication | 2020 |
| MSL Systems Limited | Administrative & support | 2005 |
| MT Electrical Group Ltd | Financial services | 2025 |
| Muir Carpentry Ltd | Construction | 2022 |
| Mulberry Court Management Company Limited | Households | 1985 |
| Mulberry Design & Build Specialists Ltd | Construction | 2011 |
| Multi Building Services Ltd | Construction | 2011 |
| Multi-Tool Precision Limited | Manufacturing | 2003 |
| Multiflooring Ltd | Construction | 2019 |
| Mums Love CBD Ltd | Wholesale & retail | 2020 |
| Muqtadir IT Limited | Information & communication | 2022 |
| Muscat Property Limited | Real estate | 2012 |
| My 7 Oath Ltd | Professional & scientific | 2025 |
| My Blockchain Ltd | Information & communication | 2025 |
| My Perfect Boiler Ltd | Construction | 2024 |
| My Woodstock Ltd | Manufacturing | 2026 |
| Mybraids Ltd | Other services | 2025 |
| Mysales.Cloud Ltd | Wholesale & retail | 2025 |
| MYX Industrial Supply Limited | Wholesale & retail | 2016 |
| N a Smith Carpentry Limited | Construction | 2007 |
| N E Surfacing Limited | Construction | 2012 |
| N J Simons Ltd | Agriculture & fishing | 2013 |
| N&G Property Holdings Ltd | Financial services | 2024 |
| N&K Consultancy and Property Management Ltd | Real estate | 2025 |
| N&L Properties (Worcs) Ltd | Construction | 2021 |
| Nachman Addiction Recovery Services Ltd | Health & social care | 2017 |
| Naina's Spice Limited | Manufacturing | 2021 |
| Nano Poly Morph Ltd | Professional & scientific | 2025 |
| Nantar Limited | Other services | 1999 |
| Nantmor Blinds Limited | Administrative & support | 1984 |
| Nantmor Holdings Limited | Financial services | 2021 |
| Nantmor Pleated Products Limited | Administrative & support | 2010 |
| Naphira Property Management Ltd | Real estate | 2023 |
| Nartey Ltd | Construction | 2015 |
| National Distribution Limited | Wholesale & retail | 2018 |
| National Star Trading Ltd | Wholesale & retail | 2021 |
| National Telecable Limited | Information & communication | 1984 |
| Navco Services Limited | Professional & scientific | 2025 |
| Nayaki Investments Ltd | Real estate | 2021 |
| NC Trading Limited | Hospitality | 2016 |
| Neac Ltd | Health & social care | 2021 |
| Neale Projects Ltd | Extraterritorial | 2013 |
| Nebula Technology Limited | Information & communication | 2011 |
| Nebulas Website Design Limited | Information & communication | 2010 |
| Necol Trading Ltd | Hospitality | 2024 |
| Nelf Limited | Information & communication | 2026 |
| Nelson Drive Developments Ltd | Construction | 2025 |
| Nepal House Limited | Hospitality | 2021 |
| Nesor Equipment Company Limited | Wholesale & retail | 2011 |
| NET 5 Limited | Professional & scientific | 1996 |
| Netstore Direct Ltd | Wholesale & retail | 2012 |
| Network Telecoms Ltd | Information & communication | 2025 |
| Neurodivergent.Investments Ltd | Financial services | 2025 |
| New Fountain House 130 Ltd | Hospitality | 2024 |
| New Game + Limited | Arts & recreation | 2025 |
| New Green Holdings Ltd | Real estate | 2026 |
| New Hope Organisation | Other services | 2023 |
| New Hope Rentals Ltd | Real estate | 2023 |