| LT Rentals Cumbria Ltd | Real estate | 2025 |
| Lune Lets Limited | Hospitality | 2026 |
| Lune Property Group Ltd | Real estate | 2026 |
| Luxemodo Ltd | Wholesale & retail | 2025 |
| Luxor Holdings Limited | Financial services | 2024 |
| M & E (Cumbria) Limited | Hospitality | 2009 |
| M & E Nuclear Consultancy Limited | Professional & scientific | 2013 |
| M & I Travel Limited | Transport & logistics | 2010 |
| M & J Lettings Limited | Real estate | 2024 |
| M & P Sporting Enterprises Ltd | Agriculture & fishing | 2006 |
| M D Hughes Plumbing Limited | Construction | 2008 |
| M E P Enterprises Limited | Real estate | 2003 |
| M H Land (Seaton) Limited | Construction | 2016 |
| M J Wilson (Cumbria) Limited | Administrative & support | 2010 |
| M Nails & Spa Ltd | Other services | 2023 |
| M&B Fluid Power Consultancy Ltd | Professional & scientific | 2020 |
| M&D Wallace E&I Ltd | Construction | 2008 |
| M&T Furnishings Limited | Wholesale & retail | 2025 |
| M&Tj Afrizim Investments Ltd | Construction | 2023 |
| M&Tj Cleaning Services Ltd | Wholesale & retail | 2023 |
| M, J & G Parr Limited | Wholesale & retail | 2015 |
| M.E.J. Holdings Limited | Professional & scientific | 2005 |
| M.G Services and Construction Ltd | Construction | 2025 |
| MA Offshore Safety and Consulting Ltd | Professional & scientific | 2025 |
| MA Workington Ltd | Hospitality | 2026 |
| MAC Contract Furniture Ltd | Manufacturing | 2012 |
| Macs Removals Limited | Transport & logistics | 2002 |
| Mahoney Building Services Limited | Construction | 2005 |
| Manor Developments (Cumbria) Limited | Real estate | 2007 |
| Marc Senhouse Limited | Real estate | 2017 |
| Mark Buchanan Property Limited | Real estate | 2018 |
| Mark Ireland Contracting Services Ltd | Agriculture & fishing | 2012 |
| Mark Richardson Construction Limited | Construction | 2025 |
| Marra AI Ltd | Information & communication | 2025 |
| Marra Motors Ltd | Wholesale & retail | 2014 |
| Marsden Accounting Limited | Professional & scientific | 2026 |
| Maryport Bodywork Centre (Car Sales) Ltd | Wholesale & retail | 2013 |
| Maryport Masonic Limited | Other services | 2015 |
| Maryport MOT Centre Limited | Wholesale & retail | 2011 |
| Maryport Tandoori Limited | Hospitality | 2023 |
| Maryport Travel Ltd | Transport & logistics | 2025 |
| Masters of Motoring Ltd | Administrative & support | 2023 |
| Matthew Sharpe Landscaping Ltd | Administrative & support | 2020 |
| Mavi Brunch Ltd | Hospitality | 2025 |
| Mavi Brunch Workington Ltd | Manufacturing | 2026 |
| Mayab Medical Consultancy Ltd | Health & social care | 2022 |
| MBS Developments (Cumbria) Limited | Real estate | 2016 |
| MC Barber Moorclose Ltd | Other services | 2025 |
| Mcclaren Ltd | Transport & logistics | 2026 |
| Mcgrady Engineering Limited | Manufacturing | 2004 |
| Mcintyre Systems Ltd | Professional & scientific | 2014 |
| Mcloughlin Project Services Limited | Information & communication | 2007 |
| Mcnicholas Consultants Ltd | Professional & scientific | 2021 |
| MCT (Cumbria) Limited | Construction | 2020 |
| MD Mcdonald Roofing Limited | Construction | 2013 |
| MDR Garage Services Ltd | Wholesale & retail | 2024 |
| Meadowsweet Limited | Professional & scientific | 2021 |
| MEC Inspections Ltd | Professional & scientific | 2024 |
| Media Gurus (Cumbria) Limited | Professional & scientific | 2026 |
| Megan Bird Online Coaching Ltd | Arts & recreation | 2025 |
| Megan's BKW Limited | Hospitality | 2025 |
| Melbreak Consulting Ltd | Information & communication | 2020 |
| Melbreak Enterprises Ltd | Hospitality | 1995 |
| Michael Carr Ltd. | Extraterritorial | 2025 |
| Midcroft Limited | Financial services | 2018 |
| Mikatech Ltd | Administrative & support | 2013 |
| Mike J Smith Consultancy Limited | Professional & scientific | 2018 |
| Milburns Solicitors Limited | Professional & scientific | 2013 |
| Millex Trade Ltd | Wholesale & retail | 2023 |
| Millstech Autos Ltd | Wholesale & retail | 2024 |
| Millweld Limited | Manufacturing | 2005 |
| Mindstar Rising Ltd | Manufacturing | 2019 |
| Missfitz Limited | Hospitality | 2025 |
| Misty Isle Management Limited | Hospitality | 2025 |
| MK Demolition & Remediation Ltd | Construction | 2025 |
| MK4 Prosperity Homes Ltd | Hospitality | 2026 |
| MKM Retail Trading Ltd | Wholesale & retail | 2022 |
| Mleczko Limited | Wholesale & retail | 2024 |
| MLR Leisure Limited | Hospitality | 2024 |
| Mobile Shop Ltd | Wholesale & retail | 2025 |
| Mockerkin Mews Limited | Real estate | 1998 |
| Mode Production Music Limited | Information & communication | 2010 |
| Monkey Madhouse (Workington) Limited | Arts & recreation | 2015 |
| Monkswood Developments Limited | Real estate | 2018 |
| Moorclose Community Centre Limited | Other services | 2007 |
| Morgas Plumbing & Heating Limited | Construction | 2015 |
| Morton Developments (Holdings) Ltd | Financial services | 2023 |
| Morton Properties (Cumbria) Limited | Construction | 2018 |
| Moss Bay Metals Limited | Wholesale & retail | 2004 |
| Mossbay Convenience Store Limited | Wholesale & retail | 2013 |
| Motwest Limited | Wholesale & retail | 2024 |
| Mountain View Property Management Ltd | Real estate | 2024 |
| Mountaintop Consulting Limited | Information & communication | 2017 |
| Move Easy Property Ltd | Real estate | 2020 |
| MR. Fa.Handyman Ltd | Construction | 2026 |
| MRP Engineering Group Ltd | Professional & scientific | 2025 |
| MS Engineering (Cumbria) Limited | Construction | 2022 |
| Msdistington Ltd | Real estate | 2024 |
| MSM Engineering Services Ltd | Construction | 2023 |
| MSM Hairdresser Ltd | Other services | 2019 |