| Merseytecproperties Ltd | Households | 2026 |
| Merton Bank Auto Body Repairs Ltd | Wholesale & retail | 2011 |
| Merton Tyres Ltd | Wholesale & retail | 2025 |
| Merx Sports Group Ltd | Wholesale & retail | 2021 |
| Metal Cage and Pallet Company Limited | Extraterritorial | 2010 |
| Metalwork and Glass Ltd | Manufacturing | 2018 |
| MG Excavations Ltd | Construction | 2025 |
| MGB Landscapes + Construction Ltd | Construction | 2020 |
| MGH Electrical (UK) Ltd | Construction | 2012 |
| MGK Plastics Limited | Construction | 2017 |
| Mgslc Investments Ltd | Real estate | 2023 |
| MH Groundworks NW Limited | Manufacturing | 2025 |
| MH Hvac Management Limited | Other services | 2017 |
| MHB Tyres Limited | Wholesale & retail | 2012 |
| MHO Insulation Ltd | Construction | 2024 |
| Miami-Pizza ST Helens Ltd | Hospitality | 2025 |
| Michael Raynor Flooring Ltd | Construction | 2022 |
| Micofion Limited | Administrative & support | 2018 |
| Micron Filtration Limited | Manufacturing | 2013 |
| Microtech Security Limited | Wholesale & retail | 2015 |
| Middlehurst Joinery Ltd | Construction | 2026 |
| Middleway Pharmacy Limited | Wholesale & retail | 2016 |
| Midgrod Properties Limited | Real estate | 2021 |
| Miko Trans Ltd | Transport & logistics | 2022 |
| Milestone Bakery Ltd | Hospitality | 2026 |
| Millervale Ltd | Real estate | 2025 |
| Millstream Pharma Limited | Wholesale & retail | 2023 |
| Milotto Competitions Ltd | Arts & recreation | 2025 |
| Milton & Chase Ltd | Construction | 2024 |
| Mimisys Ltd | Information & communication | 2024 |
| MINE2LOVE Ltd | Other services | 2018 |
| Mint Deal Property Ltd | Real estate | 2025 |
| Mintaka Projects Ltd | Construction | 2026 |
| Mirror Mirror Fashion Group Ltd | Wholesale & retail | 2023 |
| Mirror of Many Faces Ltd | Health & social care | 2023 |
| Mishahil Medlegal Ltd | Health & social care | 2026 |
| Misru Boava Ltd. | Wholesale & retail | 2022 |
| Miss Mabel Doll Limited | Administrative & support | 2017 |
| Missedcall Technologies Limited | Information & communication | 2026 |
| Mitchell Industrial Services Limited | Water & waste | 2002 |
| Mithila Construction Limited | Construction | 2025 |
| MJD Event & Technical Production Limited | Arts & recreation | 2014 |
| MJF Plumbing & Heating Services Limited | Construction | 2020 |
| MJM Cargo Ltd | Transport & logistics | 2025 |
| MJM Technology Limited | Information & communication | 2026 |
| MJM Valets Limited | Administrative & support | 2024 |
| Mjmharrington Limited | Real estate | 2023 |
| ML Logistics Ltd | Transport & logistics | 2025 |
| MLV Renovations and Plastering Ltd | Construction | 2025 |
| MM Contracting Services Limited | Administrative & support | 2016 |
| MM Tech Electrical Solutions Limited | Construction | 2016 |
| MMC Distribution Ltd | Wholesale & retail | 2023 |
| MN Distribution UK Ltd | Transport & logistics | 2019 |
| MNG Solution Ltd | Construction | 2023 |
| MOB TM Ltd | Construction | 2022 |
| Mobile WELDER24 Limited | Manufacturing | 2024 |
| Mobility (GB) Limited | Wholesale & retail | 2014 |
| Modern ROB Fashion Global Limited | Wholesale & retail | 2026 |
| Modlin Ltd | Transport & logistics | 2022 |
| Modulo Ltd | Information & communication | 2023 |
| Moklis Meah Ltd | Hospitality | 2019 |
| Moldtrans Logistics Ltd | Transport & logistics | 2021 |
| Molyneux Solar Systems Ltd | Construction | 2025 |
| Moneyminded Ltd | Education | 2015 |
| Montriond Equestrian Ltd | Wholesale & retail | 2023 |
| Moon Core Ltd | Professional & scientific | 2024 |
| Moon Road Ltd | Information & communication | 2020 |
| Moonlight Payroll Limited | Administrative & support | 2026 |
| Moore & Buckle (Flexible Packaging) Limited | Manufacturing | 1981 |
| Moorgate Imaan Healthcare Ltd | Wholesale & retail | 2024 |
| Moraine Lake Limited | Health & social care | 2019 |
| Morethanmutts Ltd | Other services | 2025 |
| Moribus Contracting Ltd | Administrative & support | 2020 |
| Mortgage Advice Bureau North West Limited | Financial services | 2008 |
| Mortgage Advice People Ltd | Financial services | 2016 |
| Mortgage Away Ltd | Other services | 2023 |
| Moss END Projects Limited | Construction | 2025 |
| Moss Nook Car Sales Ltd | Wholesale & retail | 2025 |
| Moss's ARC Limited | Wholesale & retail | 2026 |
| Mosspark Lettings Ltd | Real estate | 2021 |
| Mosspark Properties Limited | Real estate | 2025 |
| Motherwell Tank Gauging Limited | Manufacturing | 2008 |
| Motioncurve Limited | Information & communication | 2016 |
| Move N Stuff Ltd | Transport & logistics | 2023 |
| MP Rehabilitation Ltd | Health & social care | 2024 |
| MPB Asset & Energy Consulting Ltd | Professional & scientific | 2026 |
| Mpb-Fm Ltd | Construction | 2018 |
| Mpcl Limited | Real estate | 2020 |
| Mpdrive Limited | Transport & logistics | 2019 |
| MPH Training Community Interest Company | Education | 2013 |
| Mpowerment Therapy Ltd | Information & communication | 2025 |
| MQ Group Ltd | Construction | 2026 |
| Mqhiki Chiliza Limited | Public administration | 2022 |
| MR Blinds (Northwest) Ltd | Manufacturing | 2018 |
| MR MAG International Ltd | Construction | 2025 |
| MR One Group Ltd | Construction | 2026 |
| MR Pizza Food Ltd | Hospitality | 2025 |
| MR TOX Ltd | Wholesale & retail | 2017 |
| MRA Home Improvements Ltd | Real estate | 2021 |
| MRA Plastering Ltd | Construction | 2025 |