| Millers Tea Room Limited | Hospitality | 2019 |
| Milliontel Limited | Extraterritorial | 2012 |
| Mills Services Incorporated Limited | Real estate | 2022 |
| Milner & Jones Properties Ltd | Real estate | 2020 |
| Milo Shayman | Administrative & support | 2015 |
| Milohart Limited | Transport & logistics | 2017 |
| Milpool Ltd | Professional & scientific | 2025 |
| Milton Construction (UK) Limited | Construction | 2005 |
| Milton Hall Community Group | Other services | 1998 |
| MIM Training Ltd | Education | 2021 |
| Minatec Limited | Construction | 2007 |
| Mind Body and Spirit Barnsley Limited | Health & social care | 2015 |
| Mind Matters Training Ltd | Education | 2016 |
| Mindful Births Ltd | Health & social care | 2025 |
| Miners Welfare Ltd | Hospitality | 2020 |
| Mini Madhatters Sleep Consultancy Ltd | Professional & scientific | 2026 |
| Mini Me's Nurseries Ltd | Health & social care | 2009 |
| Minivox Limited | Education | 2025 |
| Minnovation Racing Limited | Wholesale & retail | 2012 |
| Minova International Limited | Mining & quarrying | 2002 |
| Minster Auto Spares & Sales Ltd | Wholesale & retail | 2025 |
| Mint Barbers Boutique Limited | Other services | 2025 |
| Mirabilia Consult Limited | Professional & scientific | 2016 |
| Mircea's Curier Limited | Transport & logistics | 2018 |
| Mirel London Constructions Ltd | Construction | 2019 |
| Miss Attitude Ltd | Extraterritorial | 2011 |
| Miss Moneypenny Limited | Wholesale & retail | 2025 |
| Miss Nail Barnsley Ltd | Other services | 2025 |
| Mister Gearbox Limited | Wholesale & retail | 2002 |
| Miszkaj Ltd | Wholesale & retail | 2023 |
| Mitchuk Health Limited | Health & social care | 2014 |
| Mithiya Retail Ltd | Wholesale & retail | 2024 |
| Mitradeuk Ltd | Wholesale & retail | 2021 |
| MJ & Co. Property Solutions Ltd | Real estate | 2018 |
| MJ Cookware Limited | Wholesale & retail | 2023 |
| MJ Food Ltd | Hospitality | 2024 |
| MJ Security Installations Ltd | Information & communication | 2021 |
| MJB Building Surveying and Roofing Services Limited | Construction | 2003 |
| MJD Flooring Limited | Construction | 2022 |
| Mjlc Financial Limited | Financial services | 2015 |
| MJM Transport Ltd | Transport & logistics | 2026 |
| Mjolnir Assets Ltd | Financial services | 2018 |
| MJT Windows & Doors Ltd | Construction | 2023 |
| MK Elites (Barnsley) Limited | Education | 2024 |
| MK Medicals Limited | Health & social care | 2005 |
| MK PUB & Restaurant Ltd | Hospitality | 2023 |
| MK Tints Limited | Other services | 2009 |
| MK1 Maintenance Solutions Limited | Administrative & support | 2010 |
| MKA Property Solutions Ltd | Real estate | 2020 |
| MKB Courier Services Ltd | Transport & logistics | 2023 |
| MKB Solicitors LLP | | 2010 |
| MKB Talent Partners Limited | Administrative & support | 2025 |
| Mkdo Ltd | Information & communication | 2013 |
| MKH Roofing and Solar Ltd | Construction | 2023 |
| MKL Property Portfolio Ltd | Real estate | 2025 |
| MKO Transport Ltd | Transport & logistics | 2025 |
| MLC (Doncaster) Limited | Wholesale & retail | 2019 |
| MLC Properties (Holdings) Limited | Real estate | 2021 |
| MLJ Property Company Limited | Real estate | 2005 |
| MM Frost Plant Ltd | Manufacturing | 2017 |
| Mmas Transport Ltd | Transport & logistics | 2022 |
| Mmiry Limited | Hospitality | 2023 |
| Mmlt Associates Limited | Professional & scientific | 2023 |
| MMN & R Limited | Health & social care | 2023 |
| MMR Solutions Limited | Information & communication | 2008 |
| MNA Commercial Group Ltd | Real estate | 2025 |
| Moba Mobile Automation Ltd | Construction | 2010 |
| Mobile Footcare Ltd | Health & social care | 2021 |
| Mobile Laser Cleaning 3000 Ltd | Administrative & support | 2025 |
| Moderna Homes Limited | Real estate | 2016 |
| Modular Buildings Limited | Manufacturing | 2024 |
| Modular Scaffolding Limited | Extraterritorial | 2006 |
| Module Limited | Real estate | 2002 |
| Moebius Ltd | Wholesale & retail | 2023 |
| Mogul SKI Ltd | Wholesale & retail | 2023 |
| Mohan Construction Supplies Ltd | Wholesale & retail | 2025 |
| Mojito Hair & Beauty Ltd | Other services | 2017 |
| Mojo Barnsley Ltd | Hospitality | 2025 |
| Mokies Transport Limited | Transport & logistics | 2012 |
| Mokkies Driving Services Limited | Transport & logistics | 2015 |
| Momentworth Ltd | Agriculture & fishing | 2025 |
| Momo Family Limited | Wholesale & retail | 2025 |
| Monassa Design Limited | Arts & recreation | 2012 |
| Moncy's Kitchen Ltd | Hospitality | 2023 |
| Moneymanager+ Limited | Professional & scientific | 2012 |
| Monfer Ltd | Transport & logistics | 2025 |
| Mongress Limited | Wholesale & retail | 2025 |
| Monitor Logistics Services Limited | Transport & logistics | 2025 |
| Monji Group Ltd | Wholesale & retail | 2025 |
| Monk Bretton Ltd | Wholesale & retail | 2026 |
| Monkstone Brew Ltd | Hospitality | 2025 |
| Monra Associates Limited | Information & communication | 1996 |
| Montage Property & Storage Limited | Real estate | 2025 |
| Montage Yorkshire Limited | Construction | 2004 |
| Monty Electrics Limited | Construction | 2018 |
| Moonlight SMC Limited | Other services | 2022 |
| Moonstead Estates Ltd | Real estate | 2003 |
| Moore & Waller Building & Roofing Limited | Other services | 2016 |
| Moore GAS Limited | Construction | 2009 |
| Moorfield Property Ltd | Real estate | 2002 |