| Morrison's Property Services Ltd | Construction | 2011 |
| Morrow Bookkeeping Ltd | Professional & scientific | 2019 |
| Mortgage Coach Advisory Limited | Financial services | 2025 |
| Mortgage Horizons Limited | Administrative & support | 2004 |
| Mortgage New Ltd | Financial services | 2019 |
| Mortgage, Protection & Finance Ltd | Financial services | 2008 |
| Mortgages Kept Simple Ltd | Financial services | 2021 |
| Mortimus Services Ltd | Construction | 2025 |
| Morv Limited | Wholesale & retail | 2020 |
| Morvic Limited | Construction | 2019 |
| Mosaics-Of-Life Therapies Ltd | Health & social care | 2021 |
| Mosh Restaurant Limited | Hospitality | 2019 |
| Mosh Takeaway Ltd | Hospitality | 2021 |
| Moshan Island Limited | Hospitality | 2013 |
| Moss & Muse Ltd | Wholesale & retail | 2025 |
| Moss Books Limited | Professional & scientific | 2024 |
| Mossyoffice.Com Ltd | Wholesale & retail | 2011 |
| Mostaff Ltd | Administrative & support | 2016 |
| Mosur Consulting Services Ltd | Professional & scientific | 2025 |
| MOT Auto Centre Ltd | Wholesale & retail | 2015 |
| Motion Enterprises Services Limited | Information & communication | 2016 |
| Motion International Limited | Administrative & support | 2005 |
| MOTIV8 Logistics Ltd | Transport & logistics | 2025 |
| Moto Cave Limited | Wholesale & retail | 2021 |
| Motor HUT Group Limited | Wholesale & retail | 2023 |
| Motorcycle Mega Stores Holding Limited | Financial services | 2024 |
| Motorcycle Mega Stores Limited | Wholesale & retail | 2012 |
| Motorcycle Workshop Ltd | Wholesale & retail | 2020 |
| Motorcycles UK (Swindon) Ltd | Wholesale & retail | 2019 |
| Mount Pleasant Industrial Ltd | Manufacturing | 2017 |
| Mountain Blue IT Solutions Ltd | Information & communication | 2011 |
| Mountain Climbers Limited | Health & social care | 2017 |
| Mouton Properties Limited | Real estate | 2025 |
| Moveability Ltd. | Other services | 2021 |
| Moveright Mortgage Consultants Limited | Financial services | 2014 |
| Moving With Matt Ltd | Real estate | 2026 |
| Moyocoyotzin Ltd | Transport & logistics | 2023 |
| Mozart Property Limited | Financial services | 2020 |
| MP Brett Ltd | Real estate | 2022 |
| MP Roofing and Solar Ltd | Construction | 2023 |
| MP Systems Ltd | Manufacturing | 2023 |
| MP Tiles Kitchens Bathrooms & Bedrooms Limited | Construction | 2014 |
| MPB Windows and Doors Limited | Construction | 2018 |
| Mpendulo Ltd | Health & social care | 2013 |
| MPH Plant/Groundworks Ltd | Construction | 2025 |
| MPK Trans PL Ltd | Transport & logistics | 2025 |
| MPM Nationwide Logistics Ltd | Transport & logistics | 2024 |
| MPN Accounts Limited | Professional & scientific | 2019 |
| MPW Construction Groundwork Ltd | Construction | 2018 |
| MPW Plant Hire Ltd | Administrative & support | 2019 |
| Mquattro Ltd | Transport & logistics | 2021 |
| MR Beancounters Ltd | Professional & scientific | 2019 |
| MR Cleaner Cleaning Services Limited | Administrative & support | 2022 |
| MR J40 Pedal Cars Ltd | Wholesale & retail | 2026 |
| MR Outdoors Ltd | Administrative & support | 2021 |
| MR Philip Nigel Oyewo Ltd | Extraterritorial | 2024 |
| MR Wajahat Ltd | Professional & scientific | 2025 |
| MR Whippie Ltd | Hospitality | 2025 |
| MR. Box Productions Ltd | Other services | 2018 |
| Mraluca Services Ltd | Transport & logistics | 2018 |
| MRC Design Solutions Limited | Professional & scientific | 2009 |
| MRK Properties Development Ltd | Construction | 2024 |
| MRO Direct Ltd | Transport & logistics | 2020 |
| MRP Caterers Ltd | Hospitality | 2019 |
| MRR Management Ltd | Construction | 2025 |
| MRT Construction & Design UK Ltd | Construction | 2025 |
| MRT Construction UK Ltd | Construction | 2019 |
| MRT JET Limited | Wholesale & retail | 2014 |
| MS Fibre Limited | Construction | 2023 |
| MS Group (UK Holdings) Limited | Financial services | 2025 |
| MS Handasah Consultants Limited | Professional & scientific | 2015 |
| MS Installations&Maintenance Ltd | Manufacturing | 2021 |
| MS Utility Services Limited | Administrative & support | 2024 |
| MS Vehicle Services (Swindon) Limited | Wholesale & retail | 2025 |
| MSB Holdings (SW) Ltd | Real estate | 2018 |
| Msdsons Limited | Health & social care | 2022 |
| MSG Vehicle Delivery Limited | Transport & logistics | 2025 |
| MSH Properties Limited | Administrative & support | 1998 |
| Msjrs Ltd | Information & communication | 2015 |
| MSK Jobs Limited | Professional & scientific | 2021 |
| Mskh Properties Limited | Real estate | 2016 |
| MSM Systems Ltd | Information & communication | 2013 |
| MSM Trading Limited | Wholesale & retail | 2016 |
| MSQ Motoring Ltd | Wholesale & retail | 2014 |
| MSS Pasta Limited | Hospitality | 2025 |
| Mssxw Services Ltd | Wholesale & retail | 2026 |
| MSW Professional Services Limited | Professional & scientific | 2016 |
| MT Consulting Engineers Ltd | Professional & scientific | 2018 |
| MT Express Limited | Transport & logistics | 2015 |
| MT Sunshine Care Limited | Health & social care | 2019 |
| Mt.Lounge Ltd | Health & social care | 2026 |
| MTD (UK & Ireland) Ltd | Construction | 2011 |
| Mtdsorted Ltd | Information & communication | 2020 |
| MTE Trading Ltd | Wholesale & retail | 2019 |
| Mtecc Ltd | Manufacturing | 2015 |
| Mtech Sales & Repairs Ltd | Wholesale & retail | 2024 |
| Mtf-Aquatics Ltd | Wholesale & retail | 2023 |
| MTI Installations Limited | Construction | 2010 |
| MTS Homecare Limited | Construction | 2005 |
| MTS Lettings Ltd | Real estate | 2022 |