| Mts.Delivery.Uk Ltd | Construction | 2023 |
| MTX Trans. Ltd | Transport & logistics | 2024 |
| MUD Dynamics Ltd | Education | 2018 |
| Muddy Squad Ltd | Wholesale & retail | 2021 |
| Mudhar Developments Ltd | Wholesale & retail | 2008 |
| Mueller Project Management Limited | Construction | 2018 |
| Muevete Fitness Limited | Arts & recreation | 2008 |
| Mughal Empire Limited | Professional & scientific | 2010 |
| Muhammad Imran Khan Ltd | Wholesale & retail | 2025 |
| Mulberry Sports Ltd | Construction | 2019 |
| Mulbury Ventures Limited | Construction | 2004 |
| Mullard Company Ltd | Health & social care | 2025 |
| Multi -AGG Supplies Ltd | Wholesale & retail | 2019 |
| Multi Construct (2013) UK Limited | Professional & scientific | 2013 |
| Multi Construction Pension Trust Limited | Financial services | 1982 |
| Multibrands Global (2008) Ltd | Hospitality | 2008 |
| Multidash Ltd. | Financial services | 2017 |
| Multidata Ltd | Information & communication | 1989 |
| Multima Limited | Information & communication | 2023 |
| Multishow Ltd | Wholesale & retail | 2019 |
| Multivac U.K. Limited | Manufacturing | 1984 |
| Mumma B’S Ltd | Health & social care | 2025 |
| Mundy Groundwork Limited | Construction | 2019 |
| Mundy Group Limited | Financial services | 2024 |
| Muniiemunz Limited | Health & social care | 2022 |
| Munin Dynamics Ltd | Professional & scientific | 2024 |
| Murat&Co Ltd | Other services | 2017 |
| Murmuration Partners Ltd | Professional & scientific | 2024 |
| Murphy Francis Creative Limited | Real estate | 2009 |
| Murphys Doggie Deli Limited | Wholesale & retail | 2019 |
| Murray & Roberts South America Limited | Mining & quarrying | 2009 |
| Murray & Roberts United Kingdom Limited | Professional & scientific | 1964 |
| Murree Traders Ltd | Wholesale & retail | 2017 |
| Murtoughs Master Carpentry Limited | Construction | 2025 |
| Music Bugs Ltd | Education | 2006 |
| Music in Education LLP | | 2017 |
| Muslix Ltd | Health & social care | 2023 |
| Muthoni Limited | Health & social care | 2016 |
| Muthukaruppan Ltd | Information & communication | 2018 |
| Muttley CRU Ltd | Information & communication | 2023 |
| MV Delivery Ltd | Transport & logistics | 2019 |
| MVA Power Limited | Administrative & support | 2025 |
| MVB Auto Repair Ltd | Wholesale & retail | 2025 |
| Mvb-Ktirio Ltd | Construction | 2019 |
| MVM Manikam Chettiar Ltd | Information & communication | 2011 |
| MVP Services Ltd | Construction | 2025 |
| MW Aviation Ltd | Manufacturing | 2024 |
| MW Drain Services Ltd | Water & waste | 2025 |
| MW Incorp Limited | Construction | 2013 |
| MW Property Renovations Ltd | Real estate | 2020 |
| MW Renovation and Constructions Ltd | Construction | 2019 |
| Mwangi Care Limited | Health & social care | 2019 |
| MWR Bricklaying & Construction Ltd | Construction | 2017 |
| MWR Plumbing and Heating (Contractors) Limited | Construction | 2005 |
| Mwsr Consulting Limited | Professional & scientific | 2013 |
| MXP Capital Holdings Ltd | Financial services | 2025 |
| MXP Trading Ltd | Wholesale & retail | 2025 |
| My Chilli Ltd | Hospitality | 2024 |
| My Christmas Pyjamas Ltd | Wholesale & retail | 2021 |
| My DUA Transports Ltd | Transport & logistics | 2026 |
| My Everyday Pyjamas Ltd | Wholesale & retail | 2021 |
| My Family Health Ltd | Wholesale & retail | 2021 |
| My Gadgets Shop Ltd | Health & social care | 2015 |
| My Health First Ltd | Financial services | 2025 |
| My Home Health Care Ltd | Health & social care | 2014 |
| My Inspections Ltd | Administrative & support | 2021 |
| My Jaecoo Ltd | Wholesale & retail | 2026 |
| My MAI & PAI 4232 Ltd | Health & social care | 2018 |
| My Mechanic (Swindon) Ltd | Wholesale & retail | 2016 |
| My Nest Investments Ltd | Real estate | 2026 |
| My Paper Vault Ltd | Professional & scientific | 2017 |
| My Paraplan Limited | Information & communication | 2025 |
| My Personal Tax Assistant Ltd | Professional & scientific | 2016 |
| My Phone Specialist Limited | Wholesale & retail | 2019 |
| My Property Pros Swindon Ltd | Administrative & support | 2024 |
| Mygasworks Ltd | Construction | 2011 |
| Myhome Market Ltd | Information & communication | 2026 |
| Myke Abbey Limited | Wholesale & retail | 2026 |
| MYL Securities Limited | Real estate | 2025 |
| Myles & Co Associates Ltd | Professional & scientific | 2006 |
| Myma Properties Limited | Real estate | 2016 |
| Mymarketr.Io Ltd | Professional & scientific | 2024 |
| Myprofi Consulting Ltd | Manufacturing | 2015 |
| Myprojectconsultancy Limited | Construction | 2026 |
| Myram Cyber Partners Ltd | Information & communication | 2026 |
| Myreach Ltd | Information & communication | 2025 |
| Myriad Legal Services Limited | Information & communication | 2021 |
| Mysrth Solutions Limited | Information & communication | 2023 |
| Mystery and Adventure Games Limited | Manufacturing | 2023 |
| Mytask Ltd | Wholesale & retail | 2022 |
| Myza GAS Division Ltd | Energy | 2022 |
| Myza Property Division Ltd | Real estate | 2026 |
| MZ Services Swindon Ltd | Transport & logistics | 2025 |
| MZ Surveys & Consulting Ltd | Professional & scientific | 2018 |
| Métier Developments Limited | Construction | 2019 |
| Métier Homes Limited | Construction | 2017 |
| Métier Investments Limited | Construction | 2016 |
| N & a Bros Limited | Wholesale & retail | 2026 |
| N & B Foods Limited | Wholesale & retail | 2004 |
| N & H Import and Export Ltd | Transport & logistics | 2015 |