| M Gill Engineering Ltd | Professional & scientific | 2024 |
| M J Slater Haulage Ltd | Transport & logistics | 2005 |
| M K Tkaczyk Limited | Health & social care | 2022 |
| M Lodge Heating & Plumbing Services Limited | Construction | 2006 |
| M Parker (Contracting) Limited | Administrative & support | 2004 |
| M Pattinson Joinery Limited | Construction | 2019 |
| M R Marine and Civils Ltd | Construction | 2026 |
| M Stainer Limited | Health & social care | 2011 |
| M W Hartley Limited | Transport & logistics | 2003 |
| M&A Properties Management Ltd | Real estate | 2026 |
| M.Woodhouse Transport(Lancaster)Limited | Transport & logistics | 1967 |
| M6 Media Ltd | Professional & scientific | 2015 |
| Maaga Ltd | Professional & scientific | 2025 |
| Mace Auctions Limited | Water & waste | 2025 |
| Mace Capital Limited | Real estate | 2026 |
| Mace Property Holdings Limited | Real estate | 2020 |
| Machine Cyber Ltd | Information & communication | 2024 |
| Mackie Properties Limited | Real estate | 2018 |
| Macneal & Painter Limited | Real estate | 2015 |
| Macol Systems Limited | Professional & scientific | 2009 |
| Macrolan Limited | Information & communication | 2023 |
| Macsiccar Ltd. | Construction | 2019 |
| Made to SEE Ltd | Information & communication | 2016 |
| Maggy Howarth Studios Ltd | Arts & recreation | 2022 |
| MAH Private Ltd | Health & social care | 2026 |
| Maiell Ltd | Professional & scientific | 2025 |
| Mainstage (Manufacturing) Limited | Manufacturing | 1989 |
| Majagbin Limited | Health & social care | 2023 |
| Major Equipment Limited | Manufacturing | 1990 |
| Major SIX Accommodation Limited | Real estate | 2019 |
| MAK 4 Leisure Ltd | Hospitality | 2024 |
| Malady Films Limited | Information & communication | 2013 |
| Malee Property Developments Limited | Real estate | 2021 |
| Mallaband Factors LLP | | 2003 |
| Mallorca Home Hunters LLP | | 2025 |
| Mammoth Scaffolding Ltd | Construction | 2020 |
| Management Control Association | Education | 1985 |
| Managing UP Ltd | Professional & scientific | 2023 |
| Manndeep Limited | Real estate | 2022 |
| Manor Podiatry Ltd | Health & social care | 2025 |
| Manor Road Hair and Beauty Limited | Other services | 2017 |
| Maplewood Training Solutions Ltd | Financial services | 2013 |
| Marawco 2 Limited | Professional & scientific | 2009 |
| Mardenn Properties Limited | Real estate | 2016 |
| Mardon Havstor Ltd | Agriculture & fishing | 1983 |
| Mardon Holdings Limited | Financial services | 2007 |
| Mardon Limited | Agriculture & fishing | 1984 |
| Margaret Cleaning Solutions Ltd | Administrative & support | 2019 |
| Margee (Lancaster) Limited | Real estate | 1956 |
| Marib Global Limited | Wholesale & retail | 2021 |
| Mark Armer Limited | Construction | 2003 |
| Mark Bell Electrical Contractor Limited | Manufacturing | 2014 |
| Mark Burrow Electrical Limited | Construction | 2014 |
| Mark Conder Contracting Limited | Administrative & support | 2018 |
| Mark Leather Physiotherapy Limited | Health & social care | 2008 |
| Mark Patterson Limited | Construction | 2007 |
| Marketics Limited | Professional & scientific | 2008 |
| Marketing Anthony J. Kerr Ltd | Professional & scientific | 2024 |
| Marksis Consultants Limited | Professional & scientific | 2012 |
| Marra People Ltd | Manufacturing | 2024 |
| Marsad Ltd | Wholesale & retail | 2023 |
| Marshalls Self Drive Limited | Administrative & support | 2005 |
| Martin Crabtree Limited | Real estate | 2002 |
| Martyn James Media Ltd | Professional & scientific | 2016 |
| Marvins Lancaster Pizza Ltd | Hospitality | 2026 |
| Mary Morris Consulting Limited | Professional & scientific | 2022 |
| Mary Morris Properties Limited | Real estate | 2022 |
| Maryvale House Management Company Limited | Households | 2002 |
| Mason Gillibrand Limited | Professional & scientific | 2014 |
| Masque Theatre School Limited | Arts & recreation | 2026 |
| Massonia Consulting Limited | Information & communication | 2026 |
| Matandan Ltd | Construction | 2019 |
| Match IT Resourcing Limited | Administrative & support | 2009 |
| Mather Restoration Ltd | Construction | 2021 |
| Mathew Harrison Pointing Limited | Construction | 2026 |
| Matsam Computer Services Ltd | Information & communication | 2014 |
| Matthew Wright Joinery Contractors Ltd | Manufacturing | 2020 |
| Mattlou Properties Ltd | Real estate | 2018 |
| Mayor Harvey Ince Ltd | Professional & scientific | 2024 |
| Mazuma Mobile Limited | Information & communication | 2006 |
| MB Holdings Limited | Real estate | 2015 |
| MB Nutrition Limited | Wholesale & retail | 2022 |
| MB3 Healthcare Ltd | Administrative & support | 2014 |
| MBH Estate Group Ltd | Real estate | 2024 |
| Mboroga Horn Consulting Ltd | Information & communication | 2021 |
| MC Resources Industries Limited | Manufacturing | 2014 |
| MC Welding Services Ltd | Manufacturing | 2009 |
| MCC Suppliers Ltd | Other services | 2010 |
| Mccann's Fish and Chips Limited | Hospitality | 2023 |
| Mccarthy Caravans Limited | Hospitality | 2004 |
| Mccarthy Holiday Parks Limited | Hospitality | 2025 |
| Mcdonnell Bell Company Limited | Wholesale & retail | 1998 |
| Mcgowan Property Renovations Ltd | Construction | 2026 |
| Mcguinness Racing Ltd | Arts & recreation | 2022 |
| Mcguires Tyres and MOT Limited | Wholesale & retail | 2014 |
| Mcneill Marine Ltd | Professional & scientific | 2025 |
| MCS Engineering Advisory Limited | Professional & scientific | 2026 |
| Mdnn Limited | Health & social care | 2026 |
| Meadow View Nether Kellet Limited | Hospitality | 2019 |
| Mears Ghyll Bridal Rooms Limited | Wholesale & retail | 2010 |