| Maverick Lean Consulting Limited | Professional & scientific | 2017 |
| MAX DEX Construction Limited | Construction | 2015 |
| Maxi Business Group Ltd | Wholesale & retail | 2024 |
| Maximum Care Recruitment, Consultancy and Services Ltd | Information & communication | 2020 |
| May-Ko Living Ltd | Real estate | 2023 |
| Maya Polenz Ltd | Professional & scientific | 2023 |
| Maybury Pubs Ltd | Hospitality | 2024 |
| Maybury Ventures Ltd | Professional & scientific | 2012 |
| Mayford 1TN Limited | Construction | 2024 |
| Mayford Equities Limited | Financial services | 2005 |
| Maypower Limited | Extraterritorial | 2011 |
| Maysway Trade Limited | Wholesale & retail | 2025 |
| Mbdc-Tech Ltd | Information & communication | 2021 |
| MBS Contracts Ltd. | Manufacturing | 2017 |
| MBS World Ltd | Information & communication | 2021 |
| MC Bespoke Blinds Limited | Construction | 2017 |
| MC Group Properties Ltd | Real estate | 2020 |
| MC Media & Lifestyles Ltd. | Information & communication | 2020 |
| MCA Engineering Group Ltd | Manufacturing | 2022 |
| Mccain Ltd | Construction | 2011 |
| Mccourt Consulting Ltd | Professional & scientific | 2023 |
| Mccue & Harrison Joiners Limited | Construction | 2003 |
| Mcdougall Homes Ltd | Real estate | 2024 |
| MCG Utilities Ltd | Energy | 2026 |
| Mcglasson Properties Limited | Hospitality | 2018 |
| Mcleod Construction Materials Ltd | Mining & quarrying | 2020 |
| Mcloughlin Groundworks Limited | Construction | 2019 |
| Mcloughlinbros Limited | Information & communication | 2025 |
| Mcpake Investments Limited | Real estate | 2025 |
| MCQ Investments Limited | Financial services | 2011 |
| MD2 Consulting Ltd | Professional & scientific | 2012 |
| ME Green Energy Solutions Ltd | Construction | 2020 |
| Meadowfield Ltd | Professional & scientific | 2023 |
| Meadowfield Motor Group Limited | Wholesale & retail | 2025 |
| Meadowfield Motors Limited | Wholesale & retail | 2003 |
| MEB Enterprise Limited | Administrative & support | 2025 |
| Mectury Ltd | Wholesale & retail | 2025 |
| Medicare Health Solutions Limited | Health & social care | 2013 |
| Medico-Legal Maternity Expert Ltd | Health & social care | 2022 |
| Medifor Ltd | Health & social care | 2016 |
| Mediterranean Bites Ltd | Hospitality | 2026 |
| Medway 14 Limited | Financial services | 2014 |
| Meeple Games Limited | Wholesale & retail | 2018 |
| Meeple World Ltd | Wholesale & retail | 2020 |
| Meezan Halal Store Limited | Wholesale & retail | 2025 |
| Megoran Tiling Ltd | Construction | 2023 |
| Meight Innovation Limited | Professional & scientific | 2014 |
| Melanie Sensicle Consulting Limited | Professional & scientific | 2015 |
| Melanie's Mandala Stones Ltd | Arts & recreation | 2021 |
| Melrose Learning Trust | Education | 2014 |
| Memed Turkish Barber Shop Ltd | Other services | 2020 |
| MEN Together CIC | Arts & recreation | 2026 |
| Mena-Desk Limited | Administrative & support | 2015 |
| Merchwise Ltd | Wholesale & retail | 2022 |
| Mercurial Artifice Limited | Professional & scientific | 2016 |
| Meritrade Ltd | Wholesale & retail | 2026 |
| Merland Rise CIC | Arts & recreation | 2026 |
| Merlin Coachworks Ltd | Wholesale & retail | 2002 |
| Merriment Farm Community Interest Company | Health & social care | 2018 |
| Merriment Wood Ltd | Agriculture & fishing | 2021 |
| Merrington Lane Ltd | Real estate | 2021 |
| MES Heating Ltd | Construction | 2014 |
| Messy Hands Productions Ltd | Information & communication | 2015 |
| Messy Little Thing Ltd | Manufacturing | 2015 |
| Metricore Systems Ltd | Wholesale & retail | 2025 |
| MF (Wycliffe House) Limited | Financial services | 2019 |
| MF Process Safety Limited | Professional & scientific | 2007 |
| MFT (Media) Ltd. | Information & communication | 2014 |
| MG Analysis Services Limited | Information & communication | 2016 |
| MG Estates Durham Ltd | Real estate | 2026 |
| MG Hairdressing Ltd | Other services | 2004 |
| MG Rentals Limited | Real estate | 2026 |
| MGB Consulting Property Management Limited | Professional & scientific | 2022 |
| MGH Homes Limited | Real estate | 2020 |
| MGH Offshore Limited | Administrative & support | 2017 |
| MGL Investments (Group) Limited | Professional & scientific | 2019 |
| Mgmt Warwickshire Ltd | Hospitality | 2021 |
| MGO Transport Limited | Transport & logistics | 2012 |
| MHB Construction and Civils Ltd | Construction | 2025 |
| MHG Leisure Ltd | Hospitality | 2021 |
| Michael Bray Holdings Limited | Financial services | 2025 |
| Michael Noble Investments | Professional & scientific | 2007 |
| Michael Pulman Limited | Extraterritorial | 1998 |
| Michael Shaw Logistics Ltd | Transport & logistics | 2025 |
| Michael Tunstall Limited | Professional & scientific | 2007 |
| Microsite Ltd | Agriculture & fishing | 2023 |
| Middlesborough PUB Company Limited | Hospitality | 2014 |
| Middleton ST George JV Limited | Real estate | 2018 |
| Midelb Altlantic Ltd | Wholesale & retail | 2023 |
| Midnight Mart Ltd | Wholesale & retail | 2025 |
| Midpoint Trade Ltd | Wholesale & retail | 2025 |
| Miine CIC | Health & social care | 2024 |
| Mikado Company Limited | Hospitality | 2022 |
| Mike Cole Driving School Limited | Education | 2026 |
| Mike Kelly Joinery Limited | Manufacturing | 2005 |
| Mike Pulman Holdings Limited | Financial services | 2010 |
| Mike Pulman Limited | Wholesale & retail | 1998 |
| Milburns Auto Repairs Limited | Wholesale & retail | 2013 |
| Mildert Capital Management Ltd | Wholesale & retail | 2024 |
| Mile Properties Limited | Real estate | 2022 |