| M&C Direct Ltd | Other services | 2021 |
| M&G Brands Ltd | Wholesale & retail | 2021 |
| M&J Darlington (Investment) Ltd | Real estate | 2024 |
| M&Jp Investments Ltd | Real estate | 2025 |
| M-Lock Locksmiths Ltd | Wholesale & retail | 2023 |
| M. Duerden Limited | Wholesale & retail | 1982 |
| M. J. Furniture Limited | Manufacturing | 2003 |
| M. T. Elec Ltd | Energy | 2017 |
| M.Clarkson(Electrical)Limited | Construction | 1971 |
| M.L. Electrical Contractors Limited | Construction | 2010 |
| M.S.M. Environmental Services Limited | Administrative & support | 1995 |
| M.T.J Care Limited | Public administration | 2019 |
| M1 Debt Advice Limited | Financial services | 2016 |
| M1 Logistics Ltd | Manufacturing | 2025 |
| M65 Marketing Academy Limited | Other services | 2019 |
| M65 Motors Ltd | Wholesale & retail | 2025 |
| M65 Vans Ltd | Wholesale & retail | 2016 |
| MA Development NW Limited | Construction | 2021 |
| MA Holdings NW Ltd | Construction | 2021 |
| MA Investment Group Holdings Ltd | Real estate | 2025 |
| MA Letting Management Limited | Real estate | 2023 |
| MA Locums NW Limited | Health & social care | 2024 |
| MA2 Security Solutions Ltd | Administrative & support | 2025 |
| MAB Business Consulting Ltd | Professional & scientific | 2026 |
| Mabel Hospitality Ltd | Hospitality | 2024 |
| Mace Electrical Contractors Limited | Construction | 2007 |
| Macks Angling Centre Limited | Wholesale & retail | 2008 |
| MAD Campers Ltd | Administrative & support | 2023 |
| MAD CNC Holdings Ltd | Financial services | 2024 |
| Madagascar Care Ltd | Health & social care | 2025 |
| MAF Traders Ltd | Wholesale & retail | 2026 |
| Mag-Mach Ltd | Construction | 2024 |
| Magic Spanner Ltd | Arts & recreation | 2016 |
| Magman Inspection Ltd | Water & waste | 2012 |
| Magnum Financial Solutions Ltd | Financial services | 2011 |
| Maimoonah Care Services Ltd | Health & social care | 2023 |
| Maine Pharma Consulting Limited | Administrative & support | 2008 |
| Maison Aura Limited | Hospitality | 2026 |
| Maizly UK Ltd | Manufacturing | 2022 |
| MAJ Healthcare Ltd | Health & social care | 2025 |
| Majestic Care Northwest Ltd | Health & social care | 2010 |
| Majestic Mobile Valeting Ltd | Administrative & support | 2021 |
| MAK Chem International Ltd | Wholesale & retail | 2019 |
| MAK Lubes International Ltd | Wholesale & retail | 2019 |
| Makeup Made Easy Limited | Wholesale & retail | 2021 |
| Making Impact Matter Ltd | Professional & scientific | 2021 |
| Making Moments Ltd | Hospitality | 2025 |
| Mako Shark Properties Limited | Real estate | 2017 |
| MAL Tool & Engineering Limited | Energy | 1985 |
| Malgorzata's Care Ltd | Public administration | 2025 |
| Malik Supplies Limited | Wholesale & retail | 2025 |
| Malisha Stores Limited | Wholesale & retail | 2012 |
| MAN Shave Barber Ltd | Other services | 2025 |
| Manch Ltd | Wholesale & retail | 2026 |
| Manchester Construction Group Limited | Construction | 2018 |
| Manchester(Northwest)Properties Ltd | Real estate | 2023 |
| Mancini Clothing Limited | Wholesale & retail | 2013 |
| Mandy's Mucky Mutts Ltd | Extraterritorial | 2025 |
| Mangulasprings Limited | Professional & scientific | 2018 |
| Manic Hill Limited | Wholesale & retail | 2025 |
| Mann Island Limited | Extraterritorial | 2015 |
| Manor Property Management Limited | Real estate | 2003 |
| Mansha Holding Ltd | Financial services | 2024 |
| Mansha Sweets Ltd | Hospitality | 2016 |
| Mansoor Smiles Ltd | Health & social care | 2023 |
| Manythingsdupsy Ltd | Wholesale & retail | 2025 |
| MAP Mortgages Ltd | Other services | 2020 |
| Mapp Media Limited | Information & communication | 2013 |
| Marbill Developments (Sabden) Limited | Manufacturing | 1974 |
| Marcel VM Ltd | Manufacturing | 2023 |
| Marco Enhanced Ltd | Manufacturing | 2017 |
| Marine Engines UK Limited | Manufacturing | 2017 |
| Mark Crossley (Holdings) Limited | Professional & scientific | 2020 |
| Mark Dobson Vehicle Services Ltd | Wholesale & retail | 2025 |
| Mark Webb Consultancy Limited | Health & social care | 2024 |
| Marketlinkalliance Ltd | Wholesale & retail | 2024 |
| Markos Petroni Ltd | Hospitality | 2026 |
| Marks Mutts Ltd | Other services | 2024 |
| Marnita Limited | Wholesale & retail | 1965 |
| Marquis & Co. (Valuers) Limited | Real estate | 1968 |
| Marrella Properties Limited | Real estate | 2020 |
| Marroc Limited | Construction | 2007 |
| Marsden's Computer Systems Limited | Information & communication | 1998 |
| Marsden's Consultancy Services Limited | Professional & scientific | 2025 |
| Marshall Blake Limited | Hospitality | 2017 |
| Martelix Ltd | Wholesale & retail | 2025 |
| Martial Arts Centres of Excellence Stourbridge Ltd | Arts & recreation | 2020 |
| Martin Collins Developments Ltd | Construction | 2014 |
| Martin Collins Joinery & Glazing Ltd | Construction | 1998 |
| Marvtech Limited | Manufacturing | 2000 |
| Marwa Care Services Ltd | Health & social care | 2023 |
| Marz Makes Ltd | Construction | 2022 |
| Masba Limited | Households | 2025 |
| Master Home Solutions Ltd | Construction | 2026 |
| Master Kitchens and Wardrobes Limited | Manufacturing | 2024 |
| Masters of Martial Arts Blackburn LLP | | 2017 |
| Material Science Burnley Limited | Manufacturing | 1983 |
| Material Science Limited | Wholesale & retail | 2015 |
| Matt & Co London Ltd | Professional & scientific | 2019 |
| Matthew Britcliffe & Co. Ltd | Professional & scientific | 2015 |