| Motorcycle Training London Ltd | Education | 2019 |
| Motors 2 Dealership Direct Limited | Wholesale & retail | 2025 |
| Moulding Trustees Limited | Other services | 2025 |
| Mount Pleasant (Pudsey) Flat Management Company Limited | Households | 1998 |
| Mount Road Gorton Management Company Limited | Households | 2003 |
| Mount Spinale Limited | Professional & scientific | 2012 |
| Mountain View Consultancy Ltd | Wholesale & retail | 2024 |
| Mountbatten Mews (Honiton) Management Company Limited | Households | 2019 |
| Mounton Management Company Limited | Households | 2003 |
| Mountstone Applications Ltd | Professional & scientific | 2011 |
| Mouse Code Ltd | Information & communication | 2017 |
| Mova Investments Ltd | Agriculture & fishing | 2022 |
| Move Smooth UK & Europe Ltd. | Administrative & support | 2010 |
| Mowbray Square Management Company Limited | Households | 2009 |
| Moxey Properties Limited | Real estate | 2017 |
| Mphv Ltd | Professional & scientific | 2025 |
| MPM Food Consulting Limited | Hospitality | 2020 |
| MPM WET Waste Ltd | Water & waste | 2022 |
| MPS Motorsport Ltd | Arts & recreation | 2025 |
| MPS Property Maintenance Ltd | Construction | 2026 |
| MR Fencing Wiltshire Limited | Construction | 2014 |
| MR FIX IT Roofing Services Ltd | Construction | 2025 |
| MR. WW Recovery Ltd | Transport & logistics | 2025 |
| MRC Heating Services Limited | Construction | 2011 |
| MRD Agricultural Hire & Services Limited | Extraterritorial | 2020 |
| MRD Farming Services Limited | Agriculture & fishing | 2025 |
| MRL Southern Projects Limited | Construction | 2017 |
| MRP Production Services Ltd | Information & communication | 2015 |
| MSC Counselling & Consultancy Ltd | Health & social care | 2023 |
| MSR Catering Ltd | Hospitality | 2020 |
| MST Invest and Company Limited | Wholesale & retail | 2020 |
| MTP Services 24/7 Ltd | Construction | 2025 |
| MTX Electrical & Engineering Ltd | Construction | 2026 |
| Mucora Therapeutics Ltd | Professional & scientific | 2021 |
| Mulgari Cars Limited | Wholesale & retail | 2019 |
| Multinational Food Store Ltd | Wholesale & retail | 2025 |
| Multitex GRP LLP | | 2005 |
| Multivance Ltd | Transport & logistics | 2025 |
| Mundys Auto Recovery Ltd | Wholesale & retail | 2020 |
| Mundys Mobile Tyres Ltd | Wholesale & retail | 2023 |
| Mungo Melvin Strategic Ltd | Professional & scientific | 2011 |
| Munich Motorworks UK Ltd | Wholesale & retail | 2020 |
| Munro Accountants Limited | Professional & scientific | 2015 |
| Munro Brown Associates Limited | Professional & scientific | 2015 |
| Munro Brown Limited | Professional & scientific | 2015 |
| Munro Business Advisors Limited | Professional & scientific | 2014 |
| Munro Construction Ltd | Construction | 2025 |
| Munshi Corporate Ltd | Hospitality | 2021 |
| Murioi Limited | Information & communication | 2022 |
| Murley Consulting Ltd | Information & communication | 2025 |
| Muse; Making Unique Spaces Exceptional Ltd | Professional & scientific | 2026 |
| Museum Wines Limited | Wholesale & retail | 2006 |
| Music First Events Ltd | Administrative & support | 2025 |
| Musical Theatre Salisbury | Administrative & support | 2023 |
| Mustard Design & Print Limited | Professional & scientific | 2023 |
| Mustard Training Ltd | Education | 2015 |
| Mutt and Sons Ltd | Wholesale & retail | 2025 |
| MV Estates Limited | Real estate | 2011 |
| MV Properties Solutions Ltd | Households | 2025 |
| Mwnh Limited | Professional & scientific | 2019 |
| Mxbay Limited | Wholesale & retail | 2023 |
| My Cabbie South Ltd | Transport & logistics | 2025 |
| My Horse Limited | Administrative & support | 2012 |
| My Payroll Limited | Professional & scientific | 2005 |
| Myarchitect Limited | Professional & scientific | 2004 |
| Mycivils Limited | Administrative & support | 2009 |
| Mycoflow Systems Ltd | Information & communication | 2025 |
| Myddelton & Major (Andover) LLP | | 2014 |
| Myddelton & Major LLP | | 2025 |
| Myfarmtoday Ltd | Professional & scientific | 2026 |
| Myfd Farming Limited | Agriculture & fishing | 2025 |
| Mygym Health & Fitness Limited | Arts & recreation | 2011 |
| Myhealthbox Ltd | Information & communication | 2020 |
| Mylor & Mawes Ltd | Wholesale & retail | 2011 |
| Mynotts Ltd | Professional & scientific | 2010 |
| Mysipp Trustees (Property) Limited | Financial services | 2005 |
| Mysipp Trustees Limited | Financial services | 2006 |
| Myssas Trustees Limited | Financial services | 2008 |
| Mystic Dawn Media Ltd | Information & communication | 2025 |
| Myzen Limited | Other services | 2018 |
| N J Redfern Ltd | Professional & scientific | 2022 |
| N L Accounting (South West) Ltd | Professional & scientific | 2021 |
| N Trollope Transport Limited | Transport & logistics | 2006 |
| N.C. Press Limited | Construction | 1978 |
| N.D Dibben Farms Limited | Agriculture & fishing | 1967 |
| N.E. Truscott (Bude) Limited | Wholesale & retail | 1947 |
| N.Seputis Builders Ltd | Construction | 2013 |
| N1 Supplies Limited | Wholesale & retail | 2020 |
| N3SG Group Ltd | Hospitality | 2024 |
| N4 Residences Limited | Real estate | 2022 |
| Naas Kitchen Ltd | Hospitality | 2025 |
| Nadder Investments Limited | Financial services | 2016 |
| Naduadua Limited | Administrative & support | 2025 |
| Nahalsen Management Limited | Households | 2001 |
| NAI and Ken's Ltd | Other services | 2023 |
| NAI Trans Ltd | Transport & logistics | 2018 |
| Naim Foods Ltd | Hospitality | 2018 |
| Nairb Controls Limited | Construction | 2014 |
| Naish Felts Limited | Manufacturing | 1993 |
| Nakita N Ltd | Health & social care | 2019 |