| Madexa Environmental Risk Solutions Ltd. | Professional & scientific | 2015 |
| Madison Court (Harworth) Residents Management Company Limited | Households | 2021 |
| Madz About Yoga Ltd | Other services | 2025 |
| Magic of KM Ltd | Hospitality | 2026 |
| Magpie Gold Limited | Wholesale & retail | 2023 |
| Maguire and Batty (Worksop) Limited | Construction | 1998 |
| MAH Retail Ltd | Wholesale & retail | 2025 |
| Maje Global Ltd | Professional & scientific | 2023 |
| MAK Property Solutions Ltd | Real estate | 2024 |
| Make Waves Advertising & Marketing Limited | Professional & scientific | 2007 |
| Malahat Group (Yorkshire) Limited | Construction | 2020 |
| Malahat Group Ltd | Construction | 2023 |
| Maltings Wholesale Ltd | Wholesale & retail | 2024 |
| Mamma Giusi's Ltd | Hospitality | 2012 |
| Mandarin Palace Takeaway Ltd | Hospitality | 2025 |
| Manlikestubbs Limited | Wholesale & retail | 2026 |
| Manton Colliery Sports and Social Club Limited | Other services | 2010 |
| Manton Fish Bar Ltd | Hospitality | 2024 |
| Manton Multi Market Ltd | Wholesale & retail | 2024 |
| Marbag Ltd | Transport & logistics | 2019 |
| Marcel Transport Limited | Transport & logistics | 2018 |
| Margin Point Ltd | Real estate | 2025 |
| Marginworks Ltd | Professional & scientific | 2025 |
| Mariocar Trans Ltd | Transport & logistics | 2026 |
| Mark Green Building Services Limited | Construction | 2016 |
| Mark Perrins Limited | Construction | 2014 |
| MARKET9JA Limited | Wholesale & retail | 2025 |
| Markham (Sheffield) Limited | Wholesale & retail | 1950 |
| Markop Transport Ltd | Transport & logistics | 2013 |
| Markscarss Ltd | Transport & logistics | 2026 |
| Maroween Ltd | Wholesale & retail | 2022 |
| Marsden Transport Ltd | Transport & logistics | 2023 |
| Marshall 1 Ltd | Construction | 2026 |
| Marshall Telecommunications Limited | Information & communication | 2022 |
| Martin Shaw IT and Engineering Solutions Limited | Information & communication | 2007 |
| Martin Starkey Training Consultancy Ltd | Education | 2024 |
| Martin UXO Consultancy Limited | Other services | 2024 |
| Martinow Ltd | Transport & logistics | 2018 |
| Masefield Property Investments Limited | Real estate | 2024 |
| Masetheartist Ltd | Wholesale & retail | 2025 |
| Masfix Garage Ltd | Wholesale & retail | 2025 |
| Maskery Mcdonnell Limited | Real estate | 2017 |
| Mason Motor Group Ltd | Wholesale & retail | 2021 |
| Mason&Moore Ltd | Construction | 2022 |
| Master Glass GB Limited | Manufacturing | 2005 |
| Masterpart Truck and BUS Limited | Wholesale & retail | 2011 |
| Matrons Care Limited | Health & social care | 2022 |
| Matrons Wellbeing, Mentoring, and Human Resources Development CIC | Administrative & support | 2024 |
| MAX Parker Auto Ltd | Wholesale & retail | 2025 |
| MAX Technologies Ltd | Administrative & support | 2020 |
| Maxi Rail Ltd | Administrative & support | 2014 |
| Maxxiom Power Solutions Limited | Wholesale & retail | 2025 |
| MB Engineering (2025) Ltd | Manufacturing | 2025 |
| MB Fencing Supplies Ltd | Wholesale & retail | 2022 |
| MB Fire Safety Limited | Administrative & support | 2021 |
| MBE Chauffeurs Ltd | Transport & logistics | 2016 |
| MC Currie IT Limited | Administrative & support | 2007 |
| MC Property Development Services Ltd | Construction | 2025 |
| Mcclure Garden Buildings Limited | Professional & scientific | 2005 |
| Mcgrath Properties Limited | Households | 2010 |
| MCH Customer Experience Ltd | Administrative & support | 2025 |
| Mchenrys Place Limited | Wholesale & retail | 2018 |
| Mcmlxxi Ltd | Transport & logistics | 2023 |
| Meaden Enterprise Ltd | Wholesale & retail | 2024 |
| Meadow Bathrooms Ltd | Wholesale & retail | 2024 |
| Medicare Systems Limited | Manufacturing | 2003 |
| Medicine Loft Ltd | Health & social care | 2020 |
| Mediright Limited | Health & social care | 2009 |
| Mediwright Limited | Extraterritorial | 2009 |
| Meds-In-Motion UK Ltd | Health & social care | 2026 |
| Megafunplay Ltd | Administrative & support | 2026 |
| Megasun Worksop Ltd | Other services | 2017 |
| Mehreen Saif Ltd | Health & social care | 2024 |
| Melbil Ltd | Hospitality | 2025 |
| Melissa Jade Ltd | Professional & scientific | 2023 |
| Mell & a Ltd | Transport & logistics | 2018 |
| Memory M8 Ltd | Information & communication | 2025 |
| Mena 123 Limited | Health & social care | 2015 |
| Mental Health-Specialist Rose Ltd | Health & social care | 2023 |
| Meriden Animal Health Limited | Extraterritorial | 1991 |
| Meridian Web Solutions Ltd | Information & communication | 2024 |
| Merlin Property Renovations Ltd | Real estate | 2026 |
| Meryno Sheepskin Ltd | Wholesale & retail | 2020 |
| Metallurgical Replication Services Limited | Administrative & support | 2008 |
| Mexborough B1 Limited | Construction | 2024 |
| MF Flooring Services Ltd | Construction | 2022 |
| MHG Portfolio Holdings Ltd | Real estate | 2026 |
| Michael Iain French Limited | Extraterritorial | 2025 |
| Micropigmentation Training and Equipment Centre Ltd. | Health & social care | 1997 |
| Middleton Academy Ltd | Education | 2023 |
| Middleton Private Capital Ltd. | Financial services | 2018 |
| Middletons Tours Ltd | Transport & logistics | 2013 |
| Midland Garage Classics Limited | Wholesale & retail | 2017 |
| Midlands Heritage Events Ltd | Administrative & support | 2023 |
| Mihaela Learning Centre Ltd | Education | 2019 |
| Mike Finnie Ltd | Administrative & support | 2011 |
| Mike Investment Ltd | Wholesale & retail | 2021 |
| Mill Fencing Ltd | Manufacturing | 2019 |
| Millie and John Ltd | Wholesale & retail | 2018 |
| Milverdex Limited | Professional & scientific | 2016 |