| Merlin Design Services Limited | Professional & scientific | 1988 |
| Merlin International Trading Limited | Wholesale & retail | 2002 |
| Merlin Investments Limited | Financial services | 2021 |
| Merlin Telecommunications Ltd | Information & communication | 2007 |
| Merlins Lane (Scarrowscant) Management Company Limited | Households | 2020 |
| Merrilees Hart Limited | Real estate | 2018 |
| Merrill Skelton Services Ltd | Construction | 2008 |
| Mesej Ltd | Professional & scientific | 2018 |
| Mesenbio Limited | Professional & scientific | 2021 |
| Mestari Limited | Wholesale & retail | 2015 |
| Meta Properties Limited | Real estate | 2023 |
| Metabolic Therapy Ltd | Wholesale & retail | 2025 |
| Metcalfe Health and Education Limited | Health & social care | 2023 |
| Methley Trustees Limited | Extraterritorial | 2010 |
| Methodist Chapel AID Limited | Financial services | 1890 |
| Meticulous Gardens Ltd | Administrative & support | 2019 |
| Metir PLC | Manufacturing | 1998 |
| Metroquote Limited | Real estate | 1987 |
| Mews 4 Limited | Households | 2017 |
| MEZ Barbers Ltd | Other services | 2024 |
| MF (Hotel Management) Limited | Hospitality | 2004 |
| MFH Trading Ltd | Wholesale & retail | 2025 |
| Mfkco Ltd | Wholesale & retail | 2021 |
| MG Commercial Vehicle Services Limited | Manufacturing | 2022 |
| MG Property Holdco Limited | Financial services | 2024 |
| MG Wealth Management Services Ltd | Financial services | 2024 |
| Mgatus Limited | Health & social care | 2022 |
| MGM Catering Ltd | Hospitality | 2024 |
| MGT Holdings Limited | Financial services | 2021 |
| Mgtm Ltd | Other services | 2020 |
| MH Apartments Limited | Hospitality | 2006 |
| Mhcp Ltd | Construction | 2019 |
| MHD Holdings Limited | Financial services | 2009 |
| MHL Contracting Limited | Extraterritorial | 2019 |
| MI Home Electrical Ltd | Construction | 2020 |
| MI Hotels Limited | Hospitality | 2022 |
| Mi-Mi- Events and Conferencing Ltd | Other services | 2013 |
| Michael COE Ltd | Information & communication | 2003 |
| Michael Hare Associates Ltd | Professional & scientific | 2014 |
| Michael Lupton Associates Limited | Manufacturing | 1995 |
| Michael Michaud UK Limited | Wholesale & retail | 2021 |
| Michael N Peach Ltd | Professional & scientific | 2014 |
| Michael Ragg Architecture & Design Limited | Professional & scientific | 2013 |
| Michael Readman Lawnmower Services Limited | Other services | 2014 |
| Michael ROE Motor Engineers LLP | | 2012 |
| Michael Sheehan Electrical Engineering Limited | Construction | 2000 |
| Michaela Shilleto Limited | Professional & scientific | 2018 |
| Michelle Allison Consultancy Limited | Professional & scientific | 2023 |
| Michelle Orman Aesthetics Ltd | Other services | 2022 |
| Mick Harper Electrical Ltd | Professional & scientific | 2010 |
| Mick Richards Ltd. | Agriculture & fishing | 2010 |
| Micro-Tech (U.K.) Ltd | Wholesale & retail | 2021 |
| Microlab Devices Ltd | Manufacturing | 2010 |
| Micrologica Systems Limited | Information & communication | 1979 |
| Micromist Ltd | Information & communication | 2019 |
| Microplat Ltd | Professional & scientific | 2024 |
| Microsaic Systems Trading Ltd | Manufacturing | 2024 |
| MID Sussex Veterinary Clinic Ltd | Professional & scientific | 2017 |
| MID Yorks Expeditions C.I.C. | Arts & recreation | 2014 |
| Midas Cleaning Ltd | Administrative & support | 2022 |
| Midas Property Group Limited | Real estate | 2017 |
| Middle Feast Ltd | Hospitality | 2021 |
| Middlemama Ltd | Professional & scientific | 2024 |
| Middlethorpe Manor Limited | Households | 2016 |
| Middlethorpe Properties (Yorkshire) Ltd | Construction | 2018 |
| Middlethorpe York Limited | Real estate | 2017 |
| Middleton Wilson Limited | Construction | 2020 |
| Midia Invest Ltd | Administrative & support | 2017 |
| Midlands Media Agency Ltd | Information & communication | 2018 |
| Midnight Lane Limited | Wholesale & retail | 2026 |
| Midway Caravans Limited | Real estate | 1963 |
| Midway House Ltd | Hospitality | 2015 |
| Midwood Properties Ltd | Real estate | 2001 |
| Miene Services Ltd | Administrative & support | 2024 |
| Mightover Limited | Extraterritorial | 1996 |
| Mikanikos Limited | Wholesale & retail | 2017 |
| Mike Bramhall (HE Consultants) Ltd | Professional & scientific | 2018 |
| Mike Buck Limited | Information & communication | 2012 |
| Mike F Jackson Consulting Ltd | Information & communication | 2007 |
| Mike Holmes Haulage Limited | Transport & logistics | 2025 |
| Mike Potter Bespoke Joinery Ltd | Construction | 2017 |
| Mike Thorpe Windows Limited | Construction | 2020 |
| Mike Winstone Consulting Limited | Professional & scientific | 2019 |
| Miker Consulting Ltd | Professional & scientific | 2019 |
| Mikro Engineering Services Limited | Professional & scientific | 2011 |
| Mila Wine Bar Ltd | Hospitality | 2026 |
| Milbrew Ventures Limited | Health & social care | 2015 |
| Milbrook Horizons Limited | Education | 2026 |
| Milburn Design Limited | Financial services | 2025 |
| Milburns Commercial Limited | Real estate | 2024 |
| Miler Ltd | Administrative & support | 2023 |
| Milestone House Childminding Ltd | Health & social care | 2025 |
| Milestone Property Maintenance Limited | Construction | 2026 |
| Milestone Work Surfaces Limited | Construction | 2022 |
| Milestonia Limited | Professional & scientific | 2024 |
| Milfeddygon Bodrwnsiwn Veterinary Group Limited | Professional & scientific | 2016 |
| Milford Farming Limited | Agriculture & fishing | 2003 |
| Milk Presents Limited | Arts & recreation | 2011 |
| Milk Studio York Limited | Hospitality | 2025 |
| Mill Cottage Memories Ltd | Other services | 2024 |