| Memories of Life Ltd | Other services | 2017 |
| Mendore Limited | Manufacturing | 2001 |
| Mental Health Counts Ltd | Health & social care | 2014 |
| Mental Health Media Limited | Information & communication | 2014 |
| Meola's Vintage Ltd | Wholesale & retail | 2022 |
| MEP Contracts Limited | Construction | 2022 |
| Meqs Consult Limited | Construction | 2010 |
| Merc Breakers Ltd | Wholesale & retail | 2020 |
| Merchant Clipper Limited | Financial services | 2000 |
| Mercury Labels Limited | Professional & scientific | 1997 |
| Mercyatwork Ltd | Extraterritorial | 2023 |
| Mereen Limited | Professional & scientific | 2016 |
| Merelda Limited | Financial services | 2014 |
| Meridian Development Company Limited | Real estate | 1991 |
| Meridian Property Partners Ltd | Real estate | 2018 |
| Merinox Limited | Administrative & support | 2000 |
| Merixo Ltd | Other services | 2025 |
| Merkle (UK) Limited | Wholesale & retail | 1998 |
| Merlo Hospitality Ltd | Hospitality | 2026 |
| Merographics Ltd | Information & communication | 2004 |
| Merrytlg Ltd | Financial services | 2026 |
| Merseyside Aluminium Doors Ltd | Construction | 2022 |
| Met-Excel Limited | Construction | 2006 |
| Meta AID Foundation | Health & social care | 2023 |
| Meta Creative Limited | Information & communication | 2022 |
| Metal-Brite Anti-Corrosive Services Limited | Extraterritorial | 1987 |
| Meter Suppliers Ltd | Wholesale & retail | 2014 |
| Metool Co. Limited | Manufacturing | 1972 |
| Metool Holdings Ltd | Financial services | 2009 |
| Metricorix AI Limited | Wholesale & retail | 2025 |
| Metrics Energy Ltd | Energy | 2024 |
| Metromedia Communications Ltd | Information & communication | 2013 |
| MEV57 Limited | Hospitality | 2024 |
| MEW Care Ltd | Health & social care | 2015 |
| Mexicali Monton Ltd | Hospitality | 2023 |
| Mezani Bar and Grill Ltd | Hospitality | 2019 |
| Mezani Grill Limited | Hospitality | 2026 |
| MF Property Services & Investments Limited | Real estate | 2024 |
| MF Traders Limited | Wholesale & retail | 2019 |
| Mfev Blockchain Ltd | Wholesale & retail | 2024 |
| MFZ Property Europe Ltd | Real estate | 2022 |
| MFZ Property UK Ltd | Real estate | 2020 |
| MGA Plumbing and Heating Ltd | Construction | 2025 |
| Mgab Ltd | Wholesale & retail | 2023 |
| Mgabadela TD Ltd | Health & social care | 2024 |
| MGJ Investments Ltd | Professional & scientific | 2016 |
| MGL Logistics Ltd | Transport & logistics | 2022 |
| MGY Solutions Limited | Administrative & support | 2025 |
| MGZ Property & Development Ltd | Real estate | 2024 |
| MH Commercials NW Ltd | Wholesale & retail | 2025 |
| MH Homes & Builders Ltd | Construction | 2025 |
| MH Medical Investments Limited | Real estate | 2024 |
| MH Private Hire Limited | Administrative & support | 2024 |
| MH Spares Limited | Wholesale & retail | 2023 |
| MH UK Wholesale Ltd | Wholesale & retail | 2024 |
| MHA Trading Oldham Limited | Wholesale & retail | 2026 |
| Mhadi&Brothers Ltd | Wholesale & retail | 2026 |
| MHC UK Limited | Professional & scientific | 2006 |
| Mhdp Holdings Ltd | Financial services | 2017 |
| MHG Fashion Ltd | Wholesale & retail | 2021 |
| MHI Developments Limited | Construction | 2020 |
| MHI Furniture Limited | Wholesale & retail | 2022 |
| MHK Pharma Ltd | Health & social care | 2024 |
| Mhtech Ltd | Information & communication | 2022 |
| MHY Investments Ltd | Real estate | 2025 |
| MHZ Group Ltd | Real estate | 2021 |
| MI & ZMI Ltd | Transport & logistics | 2026 |
| MI Casa Lets Ltd | Real estate | 2023 |
| MI Health & Care Ltd | Health & social care | 2025 |
| MI Morena Ltd | Administrative & support | 2007 |
| MIA Multi Trade Limited | Wholesale & retail | 2023 |
| Miah Associates Limited | Professional & scientific | 2019 |
| Miah's Kitchen (Grimsby) Limited | Extraterritorial | 2011 |
| Mianco Glass & PVC Windows Ltd | Manufacturing | 2023 |
| Micc Services UK Ltd | Administrative & support | 2024 |
| Michael & Ghislaine Howard Ltd | Information & communication | 2026 |
| Michael & Shermans Limited | Administrative & support | 2017 |
| Michael & Shermans Rehabilitation Limited | Administrative & support | 2017 |
| Michael & Sterling Limited | Administrative & support | 2020 |
| Michael Bamber Holdings Limited | Financial services | 2024 |
| Michael Barnett Limited | Health & social care | 2009 |
| Michael Barry Developments Limited | Construction | 2020 |
| Michael F Thackeray Financial Services Ltd | Administrative & support | 2015 |
| Michael Gray Interim Limited | Professional & scientific | 2007 |
| Michael L. Shaw (Fabrications) Limited | Manufacturing | 1981 |
| Michael Payne BSL Interpreter Ltd | Education | 2019 |
| Michael Pettifer Insurance Brokers Limited | Financial services | 2002 |
| Michael Smart Estate Agents Ltd | Real estate | 2025 |
| Michelle Donelan Limited | Professional & scientific | 2025 |
| Mickey by BS Ltd | Wholesale & retail | 2026 |
| Micro Electronic Services Ltd | Manufacturing | 1988 |
| Micro Energy Inc Ltd | Construction | 2022 |
| Microgon Limited | Professional & scientific | 2023 |
| MID Point GEO Limited | Information & communication | 2011 |
| Midas Vending and Entertainment Limited | Arts & recreation | 2023 |
| Middle East Grill & Pizza House Ltd | Hospitality | 2018 |
| Middle Knock Media Limited | Information & communication | 2017 |
| Middle Square Chambers Limited | Administrative & support | 2019 |
| Middleton Associates Holdings Limited | Financial services | 2004 |
| Middleton Associates Limited | Wholesale & retail | 1995 |