| Montezuma Group Limited | Professional & scientific | 2018 |
| Monty & Maple Limited | Wholesale & retail | 2025 |
| Moojoos Limited | Professional & scientific | 2017 |
| Moon Reach Media Ltd | Professional & scientific | 2024 |
| Moosie Management Ltd | Professional & scientific | 2024 |
| Mopheth Consultancy Limited | Professional & scientific | 2013 |
| More Than Words Training Limited | Professional & scientific | 2009 |
| Morhicor Developments Ltd | Construction | 2012 |
| Morhicor Holdings Limited | Financial services | 2015 |
| Morpho Vision Ltd | Construction | 2024 |
| Morrells Services Ltd | Construction | 1999 |
| Morris Creative Studios Ltd | Professional & scientific | 2022 |
| Morrison and Morrison Associates Ltd | Professional & scientific | 1999 |
| Morrison Travel Limited | Real estate | 2017 |
| Mortel Property Management Ltd | Real estate | 2021 |
| Motamec Limited | Wholesale & retail | 2024 |
| Motisi Consulting Ltd | Professional & scientific | 2011 |
| Mototek Limited | Wholesale & retail | 2024 |
| Motus Automotive Consulting Ltd | Other services | 2014 |
| Mouthful Marketing Ltd | Hospitality | 2023 |
| Move Media TV Ltd | Information & communication | 2018 |
| Moveassist International Limited | Information & communication | 1997 |
| Moving Shadow (UK) Limited | Information & communication | 1999 |
| Moving Shadow Limited | Information & communication | 1995 |
| Moxon Park Homes Limited | Construction | 2021 |
| MPC Stockport Limited | Arts & recreation | 2026 |
| MPS Construction Limited | Construction | 2008 |
| MR Diamond Removals Limited | Health & social care | 2024 |
| MR James Films Ltd | Information & communication | 2022 |
| MR Lean Ltd | Real estate | 2020 |
| MR Projects & Property Management Ltd | Construction | 2017 |
| MR Properties Hitchin Ltd | Real estate | 2024 |
| MRA Autos Limited | Wholesale & retail | 2021 |
| MRG Comms Limited | Information & communication | 2013 |
| MRJ Media Ltd | Professional & scientific | 2014 |
| MRM Property Developments Ltd | Real estate | 2025 |
| MRW Holdings Limited | Financial services | 2024 |
| MS Premium Services Ltd | Financial services | 2021 |
| Msjw Services Limited | Professional & scientific | 2008 |
| MSK Remapping Ltd | Wholesale & retail | 2024 |
| MSN Laboratories Europe Limited | Wholesale & retail | 2016 |
| MTS Electrical & Renewables Ltd | Construction | 2023 |
| Much Better Prospects Limited | Professional & scientific | 2019 |
| Much Group Ltd | Wholesale & retail | 2023 |
| Mudd Flower Co. Limited | Wholesale & retail | 2025 |
| Mudwall Brick Supplies Ltd | Wholesale & retail | 2022 |
| Mullan Groundworks & Civil Engineering Ltd | Construction | 2014 |
| Mullin Mcdonnell Limited | Administrative & support | 2007 |
| Multi Utility + Surfacing Ltd | Construction | 2007 |
| Mumre-Ignite CIC | Other services | 2023 |
| Munron Consultancy Limited | Professional & scientific | 2019 |
| Munts Meadow Management Limited | Hospitality | 1979 |
| Muriel Dotty Limited | Professional & scientific | 2013 |
| Murphy's Fish & Chips Ltd | Hospitality | 2017 |
| Murrayton Limited | Real estate | 1985 |
| Mushcut Ltd | Administrative & support | 2009 |
| Mushka Music Limited | Information & communication | 2005 |
| Music Business Worldwide Ltd | Information & communication | 2014 |
| Music Management (UK) Limited | Arts & recreation | 1986 |
| Must EAT (Hitchin) Ltd | Hospitality | 2022 |
| MV 02 Ltd | Hospitality | 2022 |
| MW Love Trading Ltd | Wholesale & retail | 2025 |
| My ARC Ltd | Information & communication | 2025 |
| My Ashtray Limited | Wholesale & retail | 2007 |
| My Chicken Ltd | Construction | 2011 |
| My Compliance Centre Limited | Information & communication | 2020 |
| My Sharrabang Ltd | Health & social care | 2018 |
| Mybrain International Limited | Professional & scientific | 2007 |
| Mycomplaints Ltd | Information & communication | 2024 |
| Mycore Studios Ltd | Administrative & support | 2017 |
| Myif Limited | Financial services | 2025 |
| Myrtus Ltd | Information & communication | 2026 |
| MYT Shutters Ltd | Wholesale & retail | 2020 |
| Mythos Consulting Ltd | Professional & scientific | 2003 |
| Mzof Ltd | Information & communication | 2025 |
| N&Ek Property Ltd | Real estate | 2023 |
| N&N Sheq Solutions Ltd | Construction | 2016 |
| N.A.B. Designs Limited | Extraterritorial | 1973 |
| N.A.B. Precision Engineering Limited | Extraterritorial | 1977 |
| N.A.B. Precision Tooling Limited | Construction | 1965 |
| N.A.B. Precision Tools Limited | Extraterritorial | 1986 |
| N.B.Motors Limited | Transport & logistics | 1982 |
| N.J.O Scaffolding Ltd | Construction | 2020 |
| N13 PH Ltd | Hospitality | 2026 |
| N31 PH Ltd | Hospitality | 2026 |
| N5SOUTHWOLD Limited | Professional & scientific | 2023 |
| N8 Health Limited | Health & social care | 2004 |
| Nallum Holdings Limited | Financial services | 2019 |
| Namaste Holdings Limited | Real estate | 2017 |
| Nanofluence Ltd | Administrative & support | 2019 |
| Napoli Food Group Ltd | Hospitality | 2026 |
| National Academy of Coaching Psychology Limited | Professional & scientific | 2015 |
| National Association for Language Development in the Curriculum | Other services | 2004 |
| National Back Pain Association | Other services | 1968 |
| National Wellbeing Service Limited | Information & communication | 2015 |
| Nazareth Court Limited | Real estate | 2021 |
| NC Reward Consulting Limited | Administrative & support | 2017 |
| NC Studio Limited | Professional & scientific | 2012 |
| NCA Hitchin Ltd | Hospitality | 2025 |
| NCK International Consultants Limited | Professional & scientific | 2015 |