| M.Gees Film Services Limited | Information & communication | 2013 |
| M8 CPD Ltd | Education | 2015 |
| Macken Bros Holdings Limited | Real estate | 2019 |
| Mackie Bookkeeping Limited | Professional & scientific | 2022 |
| Magnify Design Limited | Professional & scientific | 2019 |
| MALTHOUSE54 Ltd | Professional & scientific | 2015 |
| MAMA4A Properties Limited | Real estate | 2025 |
| Man's Accessories Limited | Wholesale & retail | 2022 |
| Managed Risk Solutions Servicing Ltd | Information & communication | 2025 |
| Mandrina Research Ltd | Professional & scientific | 2025 |
| Manygate Lane Management Limited | Households | 2000 |
| Marquee AV Limited | Extraterritorial | 2011 |
| Marquee One Limited | Construction | 2019 |
| Mastercrete Limited | Extraterritorial | 2013 |
| Matthee Management Consulting Services Ltd | Professional & scientific | 2015 |
| MAX Tech Construction Limited | Mining & quarrying | 2019 |
| Mayger Electrics Limited | Construction | 2022 |
| Mbanalytics Limited | Information & communication | 2015 |
| Mbike Ltd | Wholesale & retail | 2026 |
| Mbsc Accountancy&Consultancy Ltd | Professional & scientific | 2011 |
| Meded Consultancy Limited | Professional & scientific | 2004 |
| Medico Legal Ltd | Other services | 2007 |
| Medikagm Limited | Health & social care | 2023 |
| Mensarius Wealth Ltd | Financial services | 2015 |
| Merdon Properties Limited | Real estate | 2002 |
| MGS Construction Management Services Limited | Construction | 2026 |
| MGS Electrical Solutions Ltd | Construction | 2019 |
| Mhcra Limited | Real estate | 2004 |
| Michael R LEE (Surveyors) Limited | Professional & scientific | 2017 |
| MIL Consultancy Ltd | Information & communication | 2015 |
| Mingoia Ice Creams Limited | Wholesale & retail | 2025 |
| Mintern Turner Associates Ltd | Professional & scientific | 2025 |
| MK Electrical Contractors Ltd | Construction | 2023 |
| MLA International Limited | Professional & scientific | 2003 |
| MM Enigma Ltd | Wholesale & retail | 2025 |
| MN Carpentry & Construction Limited | Construction | 2018 |
| Modern Shops and Houses (Greater London) Limited | Real estate | 1958 |
| Money Honey MH Ltd | Information & communication | 2015 |
| Money Laundering Intelligence Ltd | Administrative & support | 2010 |
| Mongoose Management and Technology Ltd | Information & communication | 2015 |
| Moorhouse-Young Limited | Information & communication | 2016 |
| Mossley Hill Mansions Land Limited | Households | 2022 |
| Moteskill Limited | Real estate | 1979 |
| MOTIVE8 Ltd | Other services | 2000 |
| MOTIVE8 North Limited | Arts & recreation | 2011 |
| Motor Nest Ltd | Wholesale & retail | 2025 |
| Mouldings & Movies Ltd | Information & communication | 2016 |
| MRJ Legacy Homes Limited | Construction | 2022 |
| Mtek Solutions Electrical & Security Limited | Construction | 2022 |
| Mulberry Foster Care Ltd | Health & social care | 2015 |
| Mumbai Square Restaurant Limited | Hospitality | 2013 |
| Mumfluencer UK Ltd | Information & communication | 2020 |
| My Local Roofer Ltd | Construction | 2025 |
| N Coyne Construction Limited | Construction | 2014 |
| Nacouz Services Ltd | Information & communication | 2004 |
| Nafa General Trading Ltd | Wholesale & retail | 2026 |
| NAM Enterprises Limited | Information & communication | 2015 |
| Nanuco CIC | Administrative & support | 2025 |
| Narwhal Properties Ltd | Real estate | 2025 |
| Natural Development Solutions Limited | Administrative & support | 2013 |
| Natural Impacts Limited | Manufacturing | 2003 |
| Nestwell Holdings Limited | Real estate | 2026 |
| Networkhub Ltd | Information & communication | 2016 |
| Neutrolinx Limited | Wholesale & retail | 2025 |
| New Leaf Fostercare Limited | Health & social care | 2026 |
| Newboulds & Co Limited | Real estate | 2012 |
| Newboulds & Co Residential Sales Ltd | Real estate | 2017 |
| Nexora AI Ltd | Information & communication | 2024 |
| NIC Osborn Gymnastics Ltd | Education | 2025 |
| Ninja Hippo Ltd | Administrative & support | 2017 |
| NN Audio Visual Ltd | Manufacturing | 2026 |
| Nnpp Enterprise Limited | Health & social care | 2024 |
| Noble DEV Ltd | Administrative & support | 2017 |
| Noble Facilities Management Services Ltd | Administrative & support | 2015 |
| Noneedles Ltd | Wholesale & retail | 2025 |
| Norcliffe Ventures Limited | Financial services | 2025 |
| North Station Limited | Professional & scientific | 2003 |
| North Wake Ltd | Administrative & support | 2026 |
| Novelty Grocers Ltd | Wholesale & retail | 2019 |
| Novus Energy CSU Ltd | Professional & scientific | 2024 |
| NPQ Nails & Beauty Limited | Other services | 2023 |
| NTT Safety Services Limited | Public administration | 2013 |
| Numi Scan East London Ltd | Health & social care | 2022 |
| Nyalen Consulting Limited | Professional & scientific | 2026 |
| Odabasi Venture Capital Ltd | Real estate | 2023 |
| Odinac Ltd | Information & communication | 2015 |
| Ofba LLP | | 2025 |
| Ofba Popes Lane Ltd | Construction | 2025 |
| Offsideopinions Limited | Information & communication | 2025 |
| Old Manor House B&B Ltd | Hospitality | 2020 |
| Omid International CIC | Education | 2021 |
| Omniplexus Distribution Ltd | Wholesale & retail | 2024 |
| One Stop Beyond Limited | Professional & scientific | 1996 |
| ONE2 Events Ltd | Hospitality | 2020 |
| Onnoti Limited | Professional & scientific | 2012 |
| Onside Football Coaching Schools Limited | Education | 2021 |
| Ovitra Studio Ltd | Arts & recreation | 2025 |
| OWL Safety Consultancy Limited | Construction | 2019 |
| Paarl Energy Ltd | Construction | 2009 |
| Pacemaker Global Ltd | Information & communication | 2021 |