| Matthews & Peart Limited | Construction | 1979 |
| Matthews Buildings Limited | Construction | 2015 |
| Matthews Legal and Mediation Solutions Limited | Professional & scientific | 2021 |
| Mattress Supermarket Ltd | Wholesale & retail | 2023 |
| Maurice James Ltd | Real estate | 2025 |
| Maurice Price Ltd | Health & social care | 2016 |
| Maveli Mart Ltd | Wholesale & retail | 2025 |
| MAVEN3 Limited | Information & communication | 2004 |
| Maverick Projects Ltd | Construction | 2013 |
| MAX Bikes PR Limited | Wholesale & retail | 2011 |
| MAX Space Construction Ltd | Construction | 2018 |
| Maxfield Bros. Ltd | Professional & scientific | 2023 |
| Maximum Effort Holdings Ltd | Financial services | 2024 |
| Maxpack Enterprises Limited | Administrative & support | 2012 |
| Maxpack Group Ltd | Administrative & support | 2019 |
| Maxpack Ltd | Financial services | 2019 |
| Maxpack Products Limited | Administrative & support | 2012 |
| Maya Shanti Yoga Limited | Health & social care | 2023 |
| Mayfair Court (Broughton Astley) Management Limited | Households | 2007 |
| Mayflower Court (Southampton) Management Company Limited | Households | 1989 |
| Mayflower Court Management (NO.1) Limited | Professional & scientific | 2000 |
| Maynard's Farm Bacon Limited | Manufacturing | 2000 |
| Maynard's Property Rentals Limited | Hospitality | 2017 |
| Maystocks Management Company Limited | Households | 1994 |
| Maziva Consultancy Limited | Professional & scientific | 2024 |
| MB Interim Service Limited | Professional & scientific | 2009 |
| MBC IT Consultants Ltd | Information & communication | 2023 |
| Mbsc Limited | Administrative & support | 2023 |
| MC Financial Group Limited | Financial services | 2026 |
| MC Heating Engineer and Plumbing Ltd | Construction | 2021 |
| Mc-Mediation Limited | Professional & scientific | 2006 |
| MCA Surveys Ltd | Professional & scientific | 2021 |
| Mccloud Professional Services Ltd | Professional & scientific | 2017 |
| Mccoy James Limited | Administrative & support | 2005 |
| Mccreadie Group Limited | Financial services | 2025 |
| MCE Solutions Limited | Energy | 2015 |
| Mcentee Racing Limited | Manufacturing | 2021 |
| MCG Systems Limited | Information & communication | 1992 |
| Mcgee Limited | Professional & scientific | 1998 |
| Mcleod Law Limited | Professional & scientific | 2025 |
| Mcloughlin Trustees Ltd | Extraterritorial | 2003 |
| Mcnulty Construction Company Limited | Extraterritorial | 2006 |
| MCP Solutions Ltd | Information & communication | 2020 |
| Mcphee Associates Ltd | Professional & scientific | 2005 |
| MCS Construction and Landscape Services Limited | Construction | 2014 |
| Mcvan Ltd | Manufacturing | 2004 |
| MDH Golf Ltd | Education | 2019 |
| MDI Health Connect Ltd | Health & social care | 2023 |
| Meadow Gate Management Company Limited | Households | 2021 |
| Meadow Grove Management Limited | Real estate | 2015 |
| Meadowgrass Limited | Professional & scientific | 2016 |
| Meals by KO Limited | Hospitality | 2024 |
| Meander Spas Ltd | Health & social care | 2019 |
| Meaning Financial Limited | Financial services | 2011 |
| Measured Insights Limited | Professional & scientific | 2026 |
| Meat Master Markets Limited | Wholesale & retail | 2012 |
| Mechis Ltd | Information & communication | 2017 |
| Medeiros Beauty Limited | Other services | 2022 |
| Medical Life Wealth Management LLP | | 2012 |
| Medici Grid Limited | Energy | 2025 |
| Meduk Group Ltd | Wholesale & retail | 2019 |
| Megan Court Residents Association Limited | Households | 2001 |
| Megha Holdings Limited | Real estate | 2025 |
| Mehmet Flame Ltd | Hospitality | 2025 |
| Meisports Limited | Arts & recreation | 2021 |
| Melanie Hooson Education Ltd | Education | 2025 |
| Melati Group Limited | Real estate | 2023 |
| Melchior Wine Holdings Limited | Financial services | 2022 |
| Melhoria Education Limited | Education | 2019 |
| Meliora Systems Ltd | Professional & scientific | 2025 |
| MEM Family Ltd | Hospitality | 2024 |
| MEN Walking and Talking CIC | Health & social care | 2022 |
| Mendez Capitol Ltd | Financial services | 2026 |
| Mental Health and Well Being Services Ltd | Health & social care | 2011 |
| Mentor Financial Services Limited | Professional & scientific | 2001 |
| Meole Estate Community Action (Meca) CIC | Hospitality | 2025 |
| Meole Orchard Management Limited | Households | 2014 |
| Meole Village Stores Limited | Wholesale & retail | 2013 |
| Meot Houses & Lettings Ltd | Real estate | 2024 |
| Meot Trading Ltd | Real estate | 2024 |
| Mer-Fin Swim Ltd | Education | 2023 |
| Meraki Shrewsbury Ltd | Real estate | 2024 |
| Merchants Gate Cottingham Limited | Real estate | 2015 |
| Mercian Accountants Ltd | Professional & scientific | 2015 |
| Mercian Engineering Ltd | Professional & scientific | 2023 |
| Mercian Masterplan Limited | Administrative & support | 1977 |
| Mercian Welfare Limited | Extraterritorial | 2014 |
| Mercury Global Resources Ltd | Professional & scientific | 2026 |
| Mercury Global Resources NO.2 Ltd | Professional & scientific | 2026 |
| Merdo Hair Ltd | Other services | 2020 |
| Mere Farm Holdings Limited | Other services | 2020 |
| Mere's Edge Management Limited | Households | 2006 |
| Meredith Media Services Limited | Manufacturing | 2003 |
| Mereside European Express Limited | Administrative & support | 2007 |
| Mergenow Property Management Limited | Households | 1992 |
| Meribel Square Management Services Limited | Households | 2005 |
| Merlin Ventures Holdings Limited | Real estate | 2023 |
| Merlone Shrewsbury Limited | Hospitality | 2025 |
| Merlwood Farm Ltd | Hospitality | 2025 |
| Merton Holdings Limited | Professional & scientific | 2018 |