| Magna Vitae Enterprises Limited | Other services | 2019 |
| Maine Associates Limited | Professional & scientific | 2005 |
| Management Support Services Limited | Professional & scientific | 2008 |
| Manby Box Ltd | Manufacturing | 2008 |
| Manby Fields Management Company Limited | Households | 2016 |
| Manby Group Limited | Financial services | 2023 |
| Manby Investments Limited | Real estate | 2024 |
| Manby Motors Limited | Wholesale & retail | 2003 |
| Manby PO & Stores Ltd | Wholesale & retail | 2009 |
| Manby Showground Limited | Construction | 1967 |
| Manby Storage Services Ltd | Transport & logistics | 2019 |
| Mansfield Consultants Limited | Professional & scientific | 2019 |
| Mark Silvester Building Ltd | Construction | 2024 |
| Mark Stubbs Agriculture Limited | Construction | 2023 |
| Market Intelligence Services Limited | Administrative & support | 1994 |
| Martrel Ltd | Information & communication | 2011 |
| Marwood Holdings Limited | Financial services | 2024 |
| Marwood Properties Limited | Real estate | 2014 |
| Masons & Partners LLP | | 2021 |
| Masons (Louth) Limited | Real estate | 2008 |
| Masons (Rural) Co Unlimited | Financial services | 2020 |
| Massingberd-Mundy Distillery Ltd | Manufacturing | 2019 |
| Massingberd-Mundy Limited | Administrative & support | 2017 |
| Masson House (Louth) Limited | Households | 1978 |
| MAT Stubbs Contracting Ltd | Agriculture & fishing | 2014 |
| Matt Fountain Property Ltd | Real estate | 2022 |
| Matt Parr Autos Limited | Wholesale & retail | 2026 |
| Mayden Services Ltd | Manufacturing | 2024 |
| Mayfair Southern Ltd | Financial services | 2025 |
| MB Early Years Education Ltd | Education | 2025 |
| MBA Flooring Limited | Wholesale & retail | 2008 |
| Mcfarland's of Louth Ltd | Professional & scientific | 2014 |
| MCM (Louth) Limited | Construction | 2002 |
| MDH Utility Services Limited | Construction | 2004 |
| Meadow Machinery Limited | Wholesale & retail | 2003 |
| Meditherm Europe Limited | Manufacturing | 2012 |
| Melting Clouds Limited | Professional & scientific | 2003 |
| Meridian Investments & Holdings Limited | Households | 2023 |
| Meridian Motor Vehicles Limited | Wholesale & retail | 2023 |
| Metal & Moon Ltd | Other services | 2026 |
| MG Ubique Ltd | Professional & scientific | 2017 |
| Mhberger Limited | Information & communication | 2024 |
| MI Baby (Louth) Ltd | Wholesale & retail | 2017 |
| Michael F. Simpson Limited | Hospitality | 1978 |
| Michael Way Management Company Limited | Households | 2019 |
| Midge Mistry Ltd | Construction | 2025 |
| Mike Parker Design Limited | Administrative & support | 2014 |
| Mila's Moments Ltd | Wholesale & retail | 2025 |
| Milfand Limited | Financial services | 2013 |
| Mill Lane Farm Limited | Professional & scientific | 2010 |
| Mill Stream Retreat Ltd | Hospitality | 2021 |
| Millenium GAS Services Limited | Construction | 2002 |
| Millicent Davenport Aesthetics Ltd | Other services | 2023 |
| MJE Heating Ltd | Construction | 2020 |
| MJM Building Limited | Construction | 2016 |
| MJM Complete Engineering Solutions Ltd | Professional & scientific | 2024 |
| MJR Financial Services Limited | Extraterritorial | 2015 |
| MK Residential Homes Ltd | Real estate | 2016 |
| MM Project Services Limited | Professional & scientific | 2025 |
| Modern Masculinity C.I.C. | Health & social care | 2025 |
| MOE Inspection Ltd | Professional & scientific | 2023 |
| Molecular Holdings Limited | Information & communication | 2023 |
| Momentum Solutions Group Limited | Administrative & support | 2026 |
| Moncaster Engineering Consultancy Limited | Professional & scientific | 2026 |
| Mono-Poly Printers Limited | Manufacturing | 2005 |
| Montebello Louth Ltd | Hospitality | 2019 |
| Moorside Design Limited | Professional & scientific | 2015 |
| Morass Community Interest Company | Other services | 2022 |
| Morgan Davies Property Management Limited | Real estate | 2014 |
| Morland Management Limited | Administrative & support | 2019 |
| Motivational Mummy Limited | Arts & recreation | 2025 |
| Moto Lincs Ltd | Wholesale & retail | 2018 |
| Mould Doctor (Franchising) Limited | Professional & scientific | 2013 |
| Mould Doctor Limited | Construction | 2009 |
| Movabullz Ltd | Other services | 2026 |
| MRB Safety Ltd | Professional & scientific | 2020 |
| MRW Services Ltd | Professional & scientific | 2023 |
| MT Petrochemical Services Ltd | Mining & quarrying | 2022 |
| Munyard Limited | Manufacturing | 2019 |
| Musson Estates Ltd | Construction | 2018 |
| MX Racing Limited | Wholesale & retail | 2015 |
| MXR Bikes Limited | Wholesale & retail | 2024 |
| MXR Properties Limited | Real estate | 2020 |
| MXR Works Limited | Construction | 2018 |
| My Kinda Business Environmental Services Ltd | Professional & scientific | 2020 |
| My Kinda Business Skills Hub Ltd | Education | 2020 |
| N a P Louth Limited | Construction | 2014 |
| N H Shopfitting & Interiors Limited | Construction | 2012 |
| N J Hales Holdings Limited | Financial services | 2022 |
| N.Goodman Designs Ltd | Professional & scientific | 2007 |
| N.T Shaw of Louth LP | | 2012 |
| N.Wilkinson,Limited | Agriculture & fishing | 1936 |
| Nath Brothers Ltd | Hospitality | 2017 |
| National Summer Fruits Limited | Extraterritorial | 2003 |
| Naturawhite Ltd | Wholesale & retail | 2025 |
| Nature’S Way Colonics Ltd | Health & social care | 2019 |
| Navuro Ltd | Information & communication | 2026 |
| Naylor-Estates Ltd | Real estate | 2019 |
| Negative Carbon Group Limited | Professional & scientific | 2022 |
| Negative Carbon Power Generation Limited | Energy | 2022 |