| Morgan & Lyon Builders Limited | Construction | 2017 |
| Morgan Cameron Limited | Information & communication | 2023 |
| Morgan Kasey Properties Ltd | Construction | 2021 |
| Morgan's Bar and Grill Ltd | Hospitality | 2019 |
| Morgansetl Consulting Ltd | Professional & scientific | 2024 |
| Moriarty Professional Placements Ltd | Administrative & support | 2024 |
| Morina Building Contractors Limited | Construction | 2019 |
| Morland Homes Limited | Real estate | 2016 |
| Mormac Construction S.E. Ltd | Construction | 2013 |
| Mormac Group Ltd | Construction | 2017 |
| Morrissey's Builders of LEE Limited | Construction | 2010 |
| Mortgage Introducer Services Limited | Administrative & support | 2024 |
| Mortimer Group Limited | Real estate | 2017 |
| Mosaic Schools Learning Trust | Education | 2011 |
| Moss Forensic Accounting Limited | Professional & scientific | 2026 |
| Mother & Nest Ltd | Wholesale & retail | 2025 |
| Mother Properties Ltd | Real estate | 2021 |
| Moulton Communications Ltd | Hospitality | 2025 |
| Mounthurst Holdings Limited | Real estate | 2025 |
| Mounthurst Project Management Limited | Real estate | 2025 |
| Mounthurst Properties Limited | Real estate | 2016 |
| Move and Flow Ltd | Arts & recreation | 2025 |
| Movemint Logistics Ltd | Transport & logistics | 2026 |
| Movezz Estate Agent Ltd | Real estate | 2023 |
| Mown and Grown Limited | Professional & scientific | 2013 |
| MP Building Restoration Ltd | Construction | 2022 |
| MP Tech Services Ltd | Professional & scientific | 2024 |
| MPD Property Management Limited | Households | 2022 |
| MPM Education Services Ltd | Education | 2023 |
| MPM Homes UK Ltd | Real estate | 2022 |
| MPP (Orpington) Ltd | Administrative & support | 2024 |
| Mprc Creations Limited | Construction | 2026 |
| MPX Colour Limited | Professional & scientific | 2018 |
| Mpxam Limited | Information & communication | 2013 |
| MQ UK Holdings Ltd | Real estate | 2023 |
| MRH Pro Ltd | Information & communication | 2014 |
| MRS Films Ltd | Information & communication | 2025 |
| MRT Contractors Ltd | Construction | 2018 |
| MRT Managements Ltd | Households | 2026 |
| MRW Automotive Ltd | Wholesale & retail | 2024 |
| MS Gold Hands Limited | Construction | 2025 |
| Msash Kitchen Ltd | Hospitality | 2026 |
| Mscv Ltd | Construction | 2025 |
| MSE (UK) Limited | Manufacturing | 2004 |
| MSE Consultancy Services Limited | Construction | 2022 |
| Mshadaki Ltd | Real estate | 2018 |
| MSJ Drain Clearance Limited | Administrative & support | 2005 |
| MSL Consultants Ltd | Professional & scientific | 2023 |
| MSM Salon Ltd | Other services | 2016 |
| MSN Infotech Ltd | Information & communication | 2014 |
| MSS Food Ventures Ltd | Professional & scientific | 2016 |
| Mssm Ltd | Other services | 2024 |
| MSX Medical Limited | Health & social care | 2023 |
| MSX Property Maintanance Ltd | Households | 2024 |
| MT Blanc Capital Advisors Ltd | Financial services | 2013 |
| MT Interiors & Fixings Ltd | Construction | 2019 |
| MTR Music Ltd | Arts & recreation | 2026 |
| MTS Abseil Events Ltd | Arts & recreation | 2022 |
| Mugta Commerical Investments Ltd | Real estate | 2023 |
| Mugta Investments Ltd | Real estate | 2020 |
| Mull Harris Limited | Information & communication | 2021 |
| Multi Lettings Ltd | Other services | 2000 |
| Multi Media Finances Limited | Professional & scientific | 2018 |
| Multi-Duct Ventilation Limited | Manufacturing | 2026 |
| Multicam Media Ltd | Information & communication | 2022 |
| Multilingual Accountancy Limited | Professional & scientific | 2016 |
| Mum-Mishmash Ltd | Other services | 2025 |
| Munks Sharpish Ltd | Information & communication | 2023 |
| Mupedziso Ltd | Health & social care | 2014 |
| Murati Investments Ltd | Real estate | 2026 |
| Murati Properties Ltd | Real estate | 2022 |
| Mure Holdings Ltd | Agriculture & fishing | 2025 |
| Murli Enterprises Limited | Real estate | 2024 |
| Music Possibilities Ltd | Extraterritorial | 2014 |
| Muslimah Education Centre Limited | Education | 2020 |
| Mustard Care Ltd | Health & social care | 2020 |
| Mutahar Construction Limited | Construction | 2009 |
| Muztrans Ltd | Transport & logistics | 2009 |
| MW Office Furniture Ltd | Wholesale & retail | 2024 |
| MWA Surveying Ltd | Professional & scientific | 2022 |
| MWB Performance Limited | Professional & scientific | 2019 |
| MWS Roofing Ltd | Construction | 2024 |
| MX Investments Limited | Financial services | 2022 |
| Mxp.Co.Uk Limited | Information & communication | 2003 |
| My Air Conditioning Ltd | Construction | 2023 |
| My Closet Boutique Limited | Wholesale & retail | 2018 |
| My Farmers Markets Ltd | Extraterritorial | 2014 |
| My Filler UK Ltd | Wholesale & retail | 2025 |
| My Move Removals Limited | Transport & logistics | 2025 |
| My Party Points Limited | Information & communication | 2024 |
| My Plan DO Review Limited | Information & communication | 2019 |
| My Trauma Healing Ltd | Public administration | 2024 |
| My Tribe UK Ltd | Health & social care | 2023 |
| Mycustomr Ltd | Information & communication | 2025 |
| Myfuture Matters Services Ltd | Health & social care | 2020 |
| Mylk & Co Ltd | Households | 2025 |
| Mymy Estate Limited | Real estate | 2023 |
| Myriad Automation Limited | Professional & scientific | 2011 |
| Mysafi Homes Ltd | Real estate | 2021 |
| MYTEA2U Limited | Extraterritorial | 2011 |