| Moving Minds Dance CIC | Arts & recreation | 2025 |
| Moving Minds Psychological Management and Rehabilitation Limited | Health & social care | 2002 |
| Moving on Mortgages Ltd | Financial services | 2021 |
| Mowatt Group Ltd | Financial services | 2018 |
| Mowbray Barnabas Ltd | Real estate | 2026 |
| Mowbray Communications Ltd | Information & communication | 2004 |
| Mown Meadows (Crook) Residents Management Company Limited | Real estate | 2024 |
| Mowthorpe (UK) Ltd | Other services | 1995 |
| Moxe International (CB) Ltd | Administrative & support | 2023 |
| Moxe Recruitment Ltd | Administrative & support | 2021 |
| Moyola Limited | Professional & scientific | 1996 |
| Moyola Payroll Limited | Professional & scientific | 2020 |
| MP (Easingwold) Limited | Construction | 2013 |
| MP Roofing and Home Improvement Ltd | Construction | 2025 |
| MPD Consultancy Ltd | Professional & scientific | 2023 |
| Mpda Properties Limited | Real estate | 2017 |
| Mpgf Limited | Hospitality | 2024 |
| MPI Locum Services Limited | Health & social care | 2011 |
| Mpit Limited | Construction | 2018 |
| MPN Properties Ltd | Real estate | 2020 |
| Mpowering People Ltd | Information & communication | 2019 |
| Mppoa Limited | Households | 2025 |
| MPQ Safety Leadership Ltd | Professional & scientific | 2011 |
| Mprs Coaching Limited | Other services | 2021 |
| MPV Helmsley LLP | | 2019 |
| Mpwrhair Ltd | Manufacturing | 2026 |
| MQA Solutions Limited | Professional & scientific | 2012 |
| MR & Sons York Ltd | Transport & logistics | 2025 |
| MR Italian Cleaning Services Limited | Administrative & support | 2015 |
| MR Mobile York Ltd | Wholesale & retail | 2023 |
| MR Scoffs Ltd | Hospitality | 2017 |
| MR. Thrifty Limited | Wholesale & retail | 1984 |
| MRA Agri Plant Ltd | Manufacturing | 2022 |
| MRC Computing Technology Limited | Information & communication | 1996 |
| MRC80 Ltd | Wholesale & retail | 2025 |
| Mreps Trustees (NO 96) Limited | Professional & scientific | 2003 |
| MRM Renovations Ltd | Construction | 2024 |
| MRS Mop-It.Com Commercial Limited | Administrative & support | 2010 |
| MRS Mop-It.Com Domestic Limited | Administrative & support | 2010 |
| MRS Mop-It.Com Ironing Limited | Other services | 2015 |
| Mrs-Mop-It.Com Lets Limited | Administrative & support | 2019 |
| MRW Construction Services Ltd | Construction | 2009 |
| MRW Properties Ltd | Real estate | 2021 |
| MS2 Investment Limited | Real estate | 2016 |
| MS4 Facilities Limited | Construction | 2025 |
| MSA Bookkeeping Ltd | Financial services | 2019 |
| MSC Wireless Ltd | Information & communication | 2012 |
| Msdp Otley Limited | Health & social care | 2024 |
| MSR Media Partners Ltd | Financial services | 2019 |
| Msto Kitchens & Bars Ltd | Hospitality | 2024 |
| MT Barrel Trading Limited | Hospitality | 2018 |
| MT Plumbing & Heating Services York Ltd | Construction | 2014 |
| MT Project Services Ltd | Professional & scientific | 2018 |
| MT Property Consultancy Limited | Households | 2017 |
| MTH Construction Limited | Construction | 2018 |
| MTJ Costen Limited | Health & social care | 2021 |
| MTK Advisory Ltd | Professional & scientific | 2021 |
| Mtpc Property Investment Company Limited | Real estate | 2023 |
| MTR Properties Ltd | Real estate | 2022 |
| Mtve Ltd | Information & communication | 2025 |
| Much ADO About Nothing Limited | Extraterritorial | 1993 |
| MUD in Your Blood | Arts & recreation | 2010 |
| Mudd & Co Block Management Limited | Real estate | 2023 |
| Mudd & Co Consultant Property Surveyors, Land and Estate Agents Limited | Real estate | 2021 |
| Mudd UP Legal Ltd | Professional & scientific | 2023 |
| Mudd UP Ltd | Professional & scientific | 2018 |
| Muddy Boots (Acomb) Limited | Education | 2018 |
| Muddy Boots Group Ltd. | Other services | 2023 |
| Muddy Boots Nursery Ltd. | Education | 2010 |
| Muddy Boots Stamford Bridge Ltd. | Education | 2012 |
| Muddy Boots Wilberfoss Ltd. | Education | 2009 |
| Mudunuri Technologies Limited | Information & communication | 2024 |
| Mulay Ltd | Health & social care | 2015 |
| Mulberry Commercial Limited | Real estate | 2018 |
| Mulberry Grove (ST Fagans Cardiff) Management Company Limited | Households | 2015 |
| Mulberry Park (Caister) Residents Management Company Limited | Households | 2024 |
| Mulberry Park (Yorkshire) Ltd | Wholesale & retail | 2015 |
| Mulberry PM Ltd | Real estate | 2006 |
| Muldoons (Merryhill) Limited | Hospitality | 2006 |
| Mulgrave Developments Limited | Construction | 2013 |
| Mulgrave Homes Limited | Construction | 2013 |
| Mulgrave Properties Limited | Construction | 2015 |
| Mulgrave Property Group Limited | Construction | 2017 |
| Mulgrave Residential Limited | Construction | 2016 |
| Mulgrave Sporting Ltd | Professional & scientific | 2026 |
| Mullen & Mullen Limited | Extraterritorial | 2014 |
| Multiclubs Limited | Information & communication | 2016 |
| Multigain Limited | Manufacturing | 1998 |
| Multihope Limited | Wholesale & retail | 1997 |
| Multitots CIC | Health & social care | 2025 |
| Multytrader Limited | Wholesale & retail | 2005 |
| Mumbai NS Ltd | Hospitality | 2024 |
| Mummyfit North Leeds Ltd | Arts & recreation | 2024 |
| Muneris Socius Limited | Information & communication | 2013 |
| Municipal Construction Ltd | Construction | 2015 |
| Munnings Software Solutions Ltd | Information & communication | 2017 |
| Murmuration Coffee Co. Ltd | Manufacturing | 2022 |
| Murney Limited | Construction | 2009 |
| Murr Plant & Transport Ltd | Water & waste | 2016 |
| Murray Group Investments Limited | Financial services | 2023 |