| MAP Flooring Limited | Construction | 2024 |
| MAP Legal Recruitment Ltd | Professional & scientific | 2022 |
| Maphy Healthcare Limited | Administrative & support | 2012 |
| Maple Catering Limited | Hospitality | 2014 |
| Maple Court Investments (Lincs) Limited | Real estate | 2005 |
| Maple Energy Services Limited | Professional & scientific | 2016 |
| Maple Farms (Billinghay) Limited | Agriculture & fishing | 2010 |
| Maple House Developers Limited | Construction | 2007 |
| Maple House Properties (Lincs) Limited | Real estate | 2017 |
| Maplebeck Tree Care Ltd. | Administrative & support | 2018 |
| Maplethorpe Contractors Limited | Agriculture & fishing | 2009 |
| Maptimise Ltd | Information & communication | 2025 |
| Marathasa Properties Limited | Real estate | 2025 |
| Marbart Transport Ltd | Administrative & support | 2019 |
| Marbre Cleaning and Facility Management Limited | Administrative & support | 2025 |
| Marc Evans Freelance Driving Services Ltd | Transport & logistics | 2012 |
| Marc James Creative Ltd | Other services | 2024 |
| Marc Lamah Ltd | Health & social care | 2009 |
| Marcin Golba Ltd | Other services | 2013 |
| Marcou Properties Ltd | Real estate | 2018 |
| Marcus Hall Legal Limited | Professional & scientific | 2011 |
| Margason Couriers Ltd | Transport & logistics | 2024 |
| Marhaus Gallery Ltd | Wholesale & retail | 2025 |
| Maria's Properties Ltd | Real estate | 2017 |
| Marielle Nobbenhuis Medical Practice Ltd | Health & social care | 2017 |
| Marina Caravan Park Ltd | Hospitality | 2025 |
| Marina Park Homes (Torksey) Limited | Construction | 2025 |
| Marine Innovations Limited | Information & communication | 2022 |
| Marine Point Apartments Limited | Households | 2001 |
| Marique Ltd | Other services | 2017 |
| Marius Taxi Ltd | Transport & logistics | 2023 |
| Marjorie Lipman Ltd | Education | 2013 |
| Mark Carr & Co Limited | Professional & scientific | 2005 |
| Mark Cheetham Produce Ltd | Wholesale & retail | 2014 |
| Mark Clayson Electrical Contractors Ltd | Construction | 2002 |
| Mark Crowther Orthopaedics Ltd | Health & social care | 2020 |
| Mark Mcneil Solicitors Limited | Professional & scientific | 2007 |
| Mark Puzey Consulting Ltd | Professional & scientific | 2025 |
| Mark Shear Limited | Construction | 1998 |
| Mark Smith Wealth Management Limited | Financial services | 2008 |
| Mark Stringer Double Glazing Limited | Construction | 2005 |
| Mark Suthern 63 Limited | Professional & scientific | 2021 |
| Market Inn Ltd | Administrative & support | 2017 |
| Market Rasen Motor Company Ltd | Wholesale & retail | 2021 |
| Market Rasen Station Community Project Community Interest Company | Real estate | 2015 |
| Marketchain Ltd | Wholesale & retail | 2025 |
| Markeybee Ltd | Wholesale & retail | 2020 |
| Markings & Civils Ltd | Construction | 2021 |
| Markmortgages Limited | Financial services | 2020 |
| Marks Transport Group Ltd | Transport & logistics | 2002 |
| Marley First Ltd | Administrative & support | 1998 |
| Marluk Ltd | Transport & logistics | 2021 |
| Marmi Homes Limited | Construction | 2019 |
| Marriott & Morley (Holdings) Limited | Financial services | 2021 |
| Marriott & Morley Limited | Construction | 2013 |
| Marriott and Cook Holdings Limited | Construction | 2024 |
| Marriott Building and Groundwork Ltd | Construction | 2024 |
| Marriott Commercial Ltd | Real estate | 2025 |
| Marsh Brickwork Limited | Construction | 2023 |
| Marsh Hall Capital Partners Limited | Financial services | 2026 |
| Marshall Flow Measurement Limited | Administrative & support | 2010 |
| Marshall’S Holdings Ltd | Manufacturing | 2019 |
| Mart-Mon Ltd. | Wholesale & retail | 2013 |
| Martin Cope Limited | Health & social care | 2020 |
| Martin Flinders Electrical Ltd | Manufacturing | 2003 |
| Martin Flower Contracting Limited | Administrative & support | 2019 |
| Martin J Dobson Ltd | Other services | 2021 |
| Martin Moor Caravan Park Limited | Arts & recreation | 2008 |
| Martin Ryan Holdings Limited | Real estate | 2000 |
| Martinez Homes Limited | Real estate | 2026 |
| Martyn J Hall Ltd | Administrative & support | 2011 |
| Martyn Richardson Limited | Professional & scientific | 1997 |
| Maruti Health Care Ltd | Health & social care | 2012 |
| Marv Foundation | Health & social care | 2024 |
| Marwood Collective Ltd | Construction | 2026 |
| Mary Clifton Consulting Ltd | Professional & scientific | 2009 |
| MAS Construction and Drainage Ltd | Construction | 2020 |
| Maschio Gaspardo UK Limited | Wholesale & retail | 2018 |
| Mascot Holdings Ltd | Financial services | 2020 |
| Mason Ford Associates Limited | Construction | 2020 |
| Masouma Services Ltd | Health & social care | 2021 |
| Massam Homes & Lettings Ltd | Real estate | 2022 |
| Massam Plumbing and Heating Limited | Construction | 2022 |
| Massam Property Lettings Ltd Ltd | Real estate | 2024 |
| Massey Photography Limited | Other services | 2010 |
| Master Stonemasons Limited | Construction | 2023 |
| Master Thatcher of Lincolnshire Ltd | Construction | 2015 |
| Masushi Ltd | Wholesale & retail | 2024 |
| Mathematician Data (UK) Limited | Financial services | 2015 |
| Matons Logistics Ltd | Transport & logistics | 2025 |
| Matpix Private Ltd | Information & communication | 2026 |
| Matrix Network Services Ltd | Information & communication | 1997 |
| Matrix NS (Holdings) Limited | Financial services | 2014 |
| Matrix NS Limited | Extraterritorial | 2022 |
| Matt Butt Property Services Ltd | Other services | 2021 |
| Matt Gallimore Building Services Limited | Construction | 2020 |
| Matt Harland Ltd | Construction | 2016 |
| Matt Liddle Associates Limited | Financial services | 2016 |
| Matthew Rodgers Ltd | Professional & scientific | 2025 |
| Mattlond Services Ltd | Administrative & support | 2019 |