| Mhofu Reality Ltd | Wholesale & retail | 2023 |
| Mia's Luxe Studio Ltd | Other services | 2026 |
| Micadi Investments LLP | | 2017 |
| Micasa Holdings Limited | Real estate | 2020 |
| Micca Marketing Ltd | Professional & scientific | 2025 |
| Milecourt Properties Limited | Real estate | 2002 |
| Miles Solutions Limited | Construction | 2016 |
| Milestone Meadow Ltd | Real estate | 2024 |
| Millah Lets Ltd | Real estate | 2024 |
| Miller Bros Ltd | Construction | 2014 |
| Millyard Properties Limited | Real estate | 1994 |
| Mims Imagination Ltd | Professional & scientific | 2025 |
| Mind in Croydon Ltd | Health & social care | 1999 |
| Mind Therapy Counselling Limited | Health & social care | 2025 |
| Mindfulness Academy Limited | Education | 2022 |
| Mindkind Wellbeing Ltd | Health & social care | 2025 |
| Mindsconnect Technologies Limited | Information & communication | 2020 |
| Minicab.Com Limited | Administrative & support | 2000 |
| Minkward Limited | Construction | 1990 |
| Miramat Holdings Limited | Real estate | 2021 |
| Mirch Masala Take Aways Ltd | Hospitality | 2018 |
| Mirish Limited | Real estate | 2024 |
| Miss Recruitment Ltd | Administrative & support | 2024 |
| Mitcham Assets Limited | Real estate | 2022 |
| Mitcham Assets SPV Limited | Real estate | 2023 |
| Mitchley Avenue (Sanderstead) Limited | Households | 2002 |
| Mithraeum IT Ltd | Information & communication | 2018 |
| Mitre Property Services Limited | Real estate | 2017 |
| Mitreprize Limited | Administrative & support | 1978 |
| MJ Building and Consulting Ltd | Construction | 2023 |
| Mj-Oak Exterior Ltd | Administrative & support | 2025 |
| MJH Real Estate Limited | Real estate | 2025 |
| MJR Besteq Ltd | Information & communication | 2025 |
| MJW A/R Consulting Limited | Information & communication | 2017 |
| MK Family Ltd | Real estate | 2018 |
| MK FIX Contractors Ltd | Administrative & support | 2016 |
| MLG Communications Ltd | Information & communication | 2013 |
| MLR Engineering Works Limited | Construction | 2020 |
| MLT Interiors Limited | Construction | 2014 |
| MLT Roofing and Building Services Ltd | Construction | 2020 |
| MM Loft Conversion& Extensions Ltd | Construction | 2019 |
| MMB Pianos Limited | Other services | 2026 |
| MMI SPV 91 Ltd | Construction | 2026 |
| Mobifix Hub Limited | Wholesale & retail | 2025 |
| Mobile Lock & Safe Co. Ltd | Manufacturing | 2012 |
| Moelven UK Limited | Wholesale & retail | 1983 |
| Mokaycee Limited | Health & social care | 2025 |
| Moldex Ltd | Administrative & support | 2024 |
| Moneteq Ltd | Professional & scientific | 2025 |
| Monks Bayfern Properties Ltd | Real estate | 2017 |
| Monocle Security Limited | Information & communication | 2016 |
| Monopoly Mortgages Limited | Financial services | 2019 |
| Monument Property Developments Limited | Construction | 2017 |
| Mooradian Architectural Services Limited | Professional & scientific | 2025 |
| Moramatt Consulting Ltd | Information & communication | 2003 |
| More Than Mediterranean Ltd | Hospitality | 2022 |
| Morgan & Partners Plumbing and Heating Limited | Construction | 2019 |
| Mortac International Ltd | Financial services | 2024 |
| Morton Doors Ltd | Manufacturing | 2022 |
| Mostash Barbers Limited | Other services | 2016 |
| Mould and Damp Specialist Ltd | Construction | 2023 |
| Moulkk Limited | Wholesale & retail | 2022 |
| Mozac Ltd | Hospitality | 2024 |
| MPL Maintenance Ltd | Other services | 2012 |
| MPL Pubco Ltd | Hospitality | 2019 |
| MPS Practitioner Ltd | Health & social care | 2023 |
| MQS Logistics Solutions Ltd | Transport & logistics | 2020 |
| MR Enis Guryel Limited | Health & social care | 2014 |
| MR Fasades Ltd | Construction | 2015 |
| MR Neel Mohan Limited | Health & social care | 2010 |
| MRC FIX IT Limited | Construction | 2020 |
| Mrlt Baban Limited | Health & social care | 2020 |
| Mrrs Empire Ltd | Wholesale & retail | 2019 |
| MSL Global Investments Limited | Financial services | 2021 |
| Mugisha Group Ltd | Wholesale & retail | 2025 |
| Mullock & Gower Limited | Administrative & support | 2017 |
| Multiclass Limited | Real estate | 1988 |
| Multidimensionality Ltd | Professional & scientific | 2023 |
| Multiple Joyce Ltd | Information & communication | 2025 |
| Murassi Winery Ltd | Wholesale & retail | 2023 |
| Musk Accounting Services Limited | Professional & scientific | 2016 |
| Mussani Limited | Construction | 2013 |
| Mutt Bakery Ltd | Wholesale & retail | 2020 |
| My Home Services (Croydon) Ltd | Other services | 2022 |
| My HR Director Limited | Administrative & support | 2021 |
| My Little Tea Party Limited | Hospitality | 2023 |
| My Rehab Care Ltd | Health & social care | 2025 |
| My Welder GUY Ltd | Manufacturing | 2025 |
| Myhapro Ltd | Professional & scientific | 2024 |
| Myki Consulting Limited | Professional & scientific | 2019 |
| Myring Medical Limited | Wholesale & retail | 2019 |
| Myuedu Ltd | Education | 2020 |
| Mzco Limited | Other services | 2020 |
| N-Tech PVT Ltd | Wholesale & retail | 2023 |
| N.M.W Carpentry & Building Ltd | Construction | 2025 |
| N2K Property Ltd | Real estate | 2020 |
| Nabsal Property Ltd | Real estate | 2021 |
| Naczo Limited | Construction | 2015 |
| Nade HV Ltd | Information & communication | 2018 |
| Nadwells Ltd | Health & social care | 2023 |