| MS Communications Ltd | Manufacturing | 2015 |
| MS Performance Ltd | Wholesale & retail | 2022 |
| MS Real Estates Ltd | Real estate | 2021 |
| MS Services and Consultancy Ltd | Other services | 2020 |
| MS Snooker Ltd | Arts & recreation | 2011 |
| MS Spice & Grill Ltd | Hospitality | 2025 |
| Msb-Medical Ltd | Health & social care | 2021 |
| Msbj Ltd | Real estate | 2022 |
| MSC Roofing Limited | Construction | 2017 |
| Mshp Property Company Limited | Real estate | 2019 |
| Mslp Ltd | Health & social care | 2020 |
| MSM Plastic Surgery Limited | Health & social care | 2022 |
| Msmith Design Ltd | Professional & scientific | 2023 |
| MSR Engineering Ltd | Professional & scientific | 2026 |
| MSV Associates Ltd | Professional & scientific | 2026 |
| MSW Home Help Ltd. | Health & social care | 2013 |
| Msys Technologies Ltd | Information & communication | 2012 |
| MT Merchandising Limited | Wholesale & retail | 2024 |
| Mtaylor Clothing Limited | Wholesale & retail | 2024 |
| MTB Luxury Travel Ltd | Transport & logistics | 2023 |
| Mtchamade Ltd | Manufacturing | 2025 |
| Mtech Group Ltd | Information & communication | 2021 |
| Mteka Care Limited | Health & social care | 2013 |
| MTSN2019 Ltd | Administrative & support | 2019 |
| MU Holdings Limited | Construction | 2023 |
| Much Obliged Ltd | Other services | 2023 |
| Mukayi Solutions Ltd | Professional & scientific | 2008 |
| Mukh’Taalif Ltd | Other services | 2025 |
| Muktha Ltd | Information & communication | 2012 |
| Mukz Enterprises Ltd | Wholesale & retail | 2023 |
| Mulberry Consultants Limited | Information & communication | 1997 |
| Mulberry Wellness Ltd | Health & social care | 2023 |
| Multisport 4 Schools Limited | Education | 2026 |
| MUM2AGENT Property Assistance Ltd | Administrative & support | 2025 |
| Munat Ltd | Wholesale & retail | 2020 |
| Munch Mozza Ltd | Hospitality | 2016 |
| Munchmead Ltd | Hospitality | 2016 |
| Murray Twohig Developments Limited | Construction | 2024 |
| Murraytwohig Daedalus Holdings Ltd | Professional & scientific | 2021 |
| Murrell Equine Limited | Professional & scientific | 2005 |
| MUS Properties Ltd | Hospitality | 2024 |
| Museum Street Management Company Limited | Households | 2022 |
| Mushroom Groundworks Limited | Construction | 2010 |
| Mushroom Man.Co.Uk Limited | Wholesale & retail | 2002 |
| Music Hire Ltd | Administrative & support | 2021 |
| Musicland (UK) Limited | Wholesale & retail | 2000 |
| Muthu Foods Limited | Hospitality | 2024 |
| Mutidzwi Ltd | Real estate | 2025 |
| MVD Transport Ltd | Transport & logistics | 2024 |
| MW Asset Services Ltd | Administrative & support | 2022 |
| MW Squier Ltd | Construction | 2017 |
| MWA Properties Limited | Real estate | 2022 |
| MXK Automotive Ltd | Wholesale & retail | 2025 |
| Mxtr Industries Ltd | Professional & scientific | 2025 |
| My Bank Workforce Solutions Ltd | Administrative & support | 2017 |
| My Essex Plumber Ltd | Construction | 2026 |
| My Favourite Sandwich Holding Ltd | Hospitality | 2025 |
| My Favourite Sandwich Mayfair Ltd | Hospitality | 2025 |
| My Favourite Sandwich North Ltd | Hospitality | 2025 |
| My Favourite Sandwich Paddington Ltd | Hospitality | 2025 |
| My Favourite Sandwich Soho Ltd | Hospitality | 2025 |
| My GP Care Limited | Health & social care | 2025 |
| My Green Energy Solutions Ltd | Extraterritorial | 2024 |
| My Health and Safety Ltd | Hospitality | 2014 |
| My Hidden Talents Ltd | Professional & scientific | 2014 |
| My Little Bath Shop Ltd | Extraterritorial | 2013 |
| My Little Print Studio Limited | Manufacturing | 2025 |
| My Milk Limited | Manufacturing | 2026 |
| My Mountain Playground Ltd | Hospitality | 2015 |
| My Nutrition and Wellness Ltd | Health & social care | 2025 |
| My Own Mentor Ltd | Education | 2011 |
| My PAY Payroll Ltd | Financial services | 2025 |
| My Production Limited | Information & communication | 2008 |
| My Propfolio Ltd | Real estate | 2025 |
| My Safety Matters Ltd | Public administration | 2023 |
| My Scilly Adventure Ltd | Administrative & support | 2023 |
| My Smart Home Ltd | Construction | 2024 |
| My Smart Roof Limited | Construction | 2019 |
| My Spotlight Independent Limited | Information & communication | 2020 |
| Mybodyuk Limited | Arts & recreation | 2022 |
| Mycobrew Ltd | Wholesale & retail | 2026 |
| Mycology Nutrition Limited | Administrative & support | 2017 |
| Mycotek Ltd | Agriculture & fishing | 2021 |
| Mydy Developments Limited | Real estate | 2013 |
| Mydy Limited | Real estate | 2010 |
| Myers Scott Ltd | Information & communication | 2014 |
| Myexpertpeople Ltd | Administrative & support | 2013 |
| Myguns Ltd | Information & communication | 2023 |
| Myhome Construction Ltd | Construction | 2017 |
| Myhome Residential Ltd | Real estate | 2017 |
| Myidea Ltd | Information & communication | 2014 |
| Myleasehold Limited | Construction | 2004 |
| MYR Consulting (Europe) PTY Ltd | Professional & scientific | 2012 |
| Myriad Capital PLC | Financial services | 2013 |
| Myriad Homes Limited | Construction | 2012 |
| Myriad Housing Limited | Construction | 2012 |
| Myro Trading Ltd | Administrative & support | 2015 |
| Myrtus Care Limited | Health & social care | 2024 |
| Mystery Football Shirts Limited | Wholesale & retail | 2022 |
| MYT Dentlab Ltd | Manufacturing | 2014 |