| Medak Limited | Extraterritorial | 2011 |
| Medassist UK Limited | Financial services | 2011 |
| MEDICALL247 Ltd | Administrative & support | 2017 |
| Medusamunch Ltd | Hospitality | 2021 |
| Mega Clean Solutions Ltd | Administrative & support | 2025 |
| Megadog Consulting Limited | Information & communication | 2018 |
| Meiklebob Farming Company Limited | Agriculture & fishing | 2004 |
| Meinbank Farm | Administrative & support | 2007 |
| Melania Consulting UK Ltd | Wholesale & retail | 2018 |
| Meldrum Holdings (Carlisle) Ltd | Administrative & support | 2022 |
| Meldrum Limited | Construction | 2003 |
| Meloumïé Ltd | Wholesale & retail | 2025 |
| Membotic Ltd | Information & communication | 2024 |
| Menopause Unzipped CIC | Education | 2021 |
| Meraki Collection Ltd | Wholesale & retail | 2023 |
| Meraki Hair Lounge Ltd | Other services | 2020 |
| Merchants & Missionaries Racing LLP | | 2015 |
| Merlin Court (Carlisle) Management Company Limited | Households | 2007 |
| Messers a Kirkbride Limited | Agriculture & fishing | 2008 |
| Messrs J a Martin Limited | Administrative & support | 2008 |
| Messrs J G Gardhouse Limited | Agriculture & fishing | 2009 |
| Messrs Whitfield Limited | Agriculture & fishing | 2006 |
| MET Farming Limited | Agriculture & fishing | 2025 |
| MET Property Maintenance (Cumbria) Ltd | Extraterritorial | 2020 |
| Metal Work Solutions (UK) Limited | Manufacturing | 2006 |
| Methodist Court Management Company Limited | Households | 2016 |
| Metrical Talent Ltd | Professional & scientific | 2022 |
| MF Bespoke Landscaping & Groundworks Limited | Administrative & support | 2021 |
| MG Interior Design Limited | Wholesale & retail | 2023 |
| MG Scaffolding Ltd | Construction | 2025 |
| MGC Cumbria Ltd | Professional & scientific | 2023 |
| MGG Renewables Limited | Administrative & support | 2013 |
| MGL Autocare Limited | Wholesale & retail | 2022 |
| MH Cladding Limited | Construction | 2012 |
| MHM (Carlisle) Limited | Real estate | 2022 |
| Mhrj Limited | Hospitality | 2023 |
| MIC Turbine Ltd | Administrative & support | 2016 |
| Michael Bird Holdings Ltd | Financial services | 2024 |
| Michael Glass Developments Limited | Professional & scientific | 2007 |
| Michael Marsh Ltd | Construction | 2020 |
| Michael Ritchie Couriers Ltd | Transport & logistics | 2018 |
| Michael Schroeder Books Limited | Information & communication | 2016 |
| Michael Thompson (Public Works Contractors and Engineers) Limited | Construction | 1935 |
| Michael Thompson Holdings Limited | Financial services | 2025 |
| Michael Thompson Property Limited | Real estate | 2002 |
| Micro IT Solutions Limited | Wholesale & retail | 2014 |
| Microfit Healthcare Services Limited | Health & social care | 2022 |
| Mike Forrester (Construction) Limited | Construction | 2002 |
| Mike Jones Painters and Decorators Ltd | Construction | 2023 |
| Mike Renew House Ltd | Construction | 2025 |
| Milano Exports Ltd | Wholesale & retail | 2026 |
| Milano Pizza House Limited | Hospitality | 2020 |
| Milano Takeaway (Carlisle) Ltd | Hospitality | 2024 |
| Milbourn's of Walby | Agriculture & fishing | 2009 |
| Milbourne Court (Carlisle) Limited | Households | 2007 |
| Miles Macinnes Court RTM Company Limited | Real estate | 2014 |
| Milestone House Management Company Limited | Extraterritorial | 2025 |
| Milestone Surveying and Engineering Ltd | Professional & scientific | 2024 |
| Mill Rigg Cottage Ltd | Hospitality | 2024 |
| Millardpemberton Limited | Hospitality | 2023 |
| Miller Trading Limited | Construction | 2017 |
| Miller's Roofing Services Limited | Construction | 2016 |
| Millgate Close Management Limited | Households | 2024 |
| Millichip Ltd | Real estate | 2010 |
| Mindful Pause Ltd | Information & communication | 2021 |
| Mindset Security Limited | Administrative & support | 2021 |
| Minihan Mcalister Limited | Professional & scientific | 2013 |
| Minimix Carlisle Ltd | Hospitality | 2026 |
| Minstergate Sales and Marketing Limited | Professional & scientific | 2011 |
| Mintsfeet Kendal Limited | Real estate | 2022 |
| Mintsfeet Limited | Real estate | 1999 |
| Minutes to Midnight Limited | Hospitality | 2017 |
| Miracle Centre Limited | Health & social care | 2019 |
| Mirador Properties | Real estate | 2019 |
| Miresdale Dairy Holding Limited | Agriculture & fishing | 2020 |
| Miresdale Dairy Limited | Agriculture & fishing | 2009 |
| Mitchell Farms Limited | Administrative & support | 2007 |
| Mitchell Surfacing Ltd | Construction | 2020 |
| Mitchells Mini Coaches Ltd | Transport & logistics | 2008 |
| Mitchinson Estates Ltd | Real estate | 2025 |
| Mitchinson Sourcing Ltd | Administrative & support | 2025 |
| Mitton Enterprises Limited | Professional & scientific | 2025 |
| Mitton Refrigeration Limited | Real estate | 1950 |
| MJR (Carlisle) Limited | Hospitality | 2016 |
| Mkwr Ltd | Hospitality | 2025 |
| MKY Dynamic Limited | Wholesale & retail | 2025 |
| ML3 Technical Services Limited | Hospitality | 2011 |
| MM Commercials Ltd | Wholesale & retail | 2019 |
| MM Supply Co. Ltd | Wholesale & retail | 2025 |
| MMK Estates Ltd | Real estate | 2024 |
| MMR Capital Group Ltd | Financial services | 2025 |
| MMR Solutions Hub Ltd | Administrative & support | 2023 |
| Mmtr Ltd | Hospitality | 2018 |
| MN Management & Consultancy Ltd | Information & communication | 2023 |
| Mobile Zone Accessories Limited | Wholesale & retail | 2023 |
| MOBILITY4HOME Ltd | Wholesale & retail | 2020 |
| Modus Brands Ltd | Wholesale & retail | 2024 |
| Mohar Ltd | Health & social care | 2021 |
| Moller-Vogel Ltd | Professional & scientific | 2021 |
| Mollie’S Cafe and Bistro Limited | Hospitality | 2025 |