| MONEY2U Limited | Other services | 2004 |
| Monitor Systems (Cumbria) Limited | Administrative & support | 2001 |
| Monkhill Developments Ltd | Real estate | 2020 |
| Monkstown Limited | Professional & scientific | 2018 |
| Monsieur Hamlet Limited | Wholesale & retail | 2026 |
| Monstroleads Ltd | Professional & scientific | 2022 |
| Monterey House Management Company Limited | Households | 2022 |
| Montpelier Professional (Borders) Limited | Professional & scientific | 2006 |
| Monty & Mabel's Natural Dog Treats Ltd | Wholesale & retail | 2024 |
| MOO MOO Consultancy Limited | Professional & scientific | 2021 |
| MOO2EWE Limited | Agriculture & fishing | 2017 |
| Moon Barbers Style Ltd | Other services | 2025 |
| Moon Limited | Professional & scientific | 1981 |
| Moor Park (Cockermouth) Limited | Real estate | 2015 |
| Mooredge Construction Ltd | Construction | 2022 |
| Mooredge Properties Ltd | Construction | 2024 |
| Moorhouse Courtyard Residents (Carlisle) Ltd | Households | 2022 |
| Moorhouse Road Property Management Limited | Households | 2016 |
| Moranos Express Ltd | Hospitality | 2020 |
| Moranos Fast Food Limited | Extraterritorial | 2018 |
| Morcant Johannes Ltd. | Manufacturing | 2018 |
| More Storage 4U Ltd | Other services | 2019 |
| Morgan Consult & Advisory Ltd | Professional & scientific | 2023 |
| Morganella's (Cumbria) Ltd | Hospitality | 2026 |
| Morganella's LLP | | 2024 |
| Morgankasieradj Ltd | Arts & recreation | 2024 |
| Morley Dairy Farming Company | Agriculture & fishing | 2022 |
| Morrey Ltd | Construction | 2020 |
| Morris N Limited | Wholesale & retail | 2008 |
| Morritt Communications Ltd | Professional & scientific | 2022 |
| Morton Business Services Ltd | Real estate | 2009 |
| Morton Cottage Residential Home Limited | Health & social care | 2004 |
| Morton Dynamics Limited | Information & communication | 2023 |
| Morton Fryer Ltd | Wholesale & retail | 2020 |
| Morton Garden Buildings Ltd | Construction | 2010 |
| Morton Motor Traders Ltd | Wholesale & retail | 2026 |
| Moss Knowe Farm Limited | Agriculture & fishing | 2025 |
| MOTIV8 Overland Traction Limited | Transport & logistics | 2013 |
| Motor Consultants Limited | Professional & scientific | 2011 |
| Mots R US Ltd | Wholesale & retail | 2025 |
| Mounsey Estates Limited | Real estate | 2025 |
| MOVE2PROPERTY Ltd | Administrative & support | 2015 |
| Moynansmith Limited | Professional & scientific | 2016 |
| Moynansmith Tax Advisory Services Limited | Professional & scientific | 2020 |
| MP Cupac Ltd | Real estate | 2022 |
| MP Cupac Tutoring Services Ltd | Education | 2022 |
| MPG Properties Ltd | Real estate | 2014 |
| MPP (Carlisle) Limited | Administrative & support | 2023 |
| MR Browns Brampton Ltd | Hospitality | 2025 |
| MR Bule Mini Market Ltd | Wholesale & retail | 2025 |
| MR Cook Limited | Hospitality | 2026 |
| MR Grey Developments Limited | Households | 2021 |
| MR Grey Estates Limited | Real estate | 2019 |
| MR Moga Limited | Construction | 2016 |
| MRM County Ltd | Wholesale & retail | 2021 |
| MS Auto Repairs Limited | Wholesale & retail | 2011 |
| MS Laidlow Joinery Limited | Construction | 2010 |
| MS Site Engineering Ltd | Construction | 2019 |
| MS Trading Limited | Transport & logistics | 2015 |
| MSL Interiors Limited | Wholesale & retail | 2003 |
| MST Deliveries Ltd | Transport & logistics | 2026 |
| MTB IT Consulting Limited | Information & communication | 2016 |
| Mtec Electrical Engineers & Contractors Ltd | Construction | 2020 |
| Mtec Holdings Ltd | Financial services | 2026 |
| Muirfield Marketing Limited | Wholesale & retail | 1999 |
| Mulberry Mews (Wetheral) Management Company Limited | Households | 2019 |
| Multi-Rend NW Limited | Construction | 2017 |
| Multiplier Audio Ltd | Information & communication | 2019 |
| Multiweigh UK Limited | Wholesale & retail | 2018 |
| Mumbai Ltd | Hospitality | 2018 |
| Munchkins (Carlisle) Limited | Health & social care | 2003 |
| Munroe Aesthetics Clinic Ltd | Health & social care | 2025 |
| Murdoch Freight Ltd | Transport & logistics | 2022 |
| Murdoch Property Management | Real estate | 2022 |
| Murray Gibson Services Limited | Construction | 2003 |
| Musical Crime Productions Ltd | Information & communication | 2023 |
| MW Properties CB Limited | Real estate | 2024 |
| Mwbr Ltd | Hospitality | 2025 |
| MWL Plaining Ltd | Manufacturing | 2017 |
| My Detailing Garage Ltd | Wholesale & retail | 2024 |
| My Dream Turnip Limited | Real estate | 2021 |
| My Shop Mate Impex Ltd | Wholesale & retail | 2026 |
| Myretirement Ltd | Financial services | 2014 |
| Myriad Leisure Ltd | Professional & scientific | 2018 |
| MZP Automation Limited | Manufacturing | 2024 |
| N & C Taxi Service Ltd | Transport & logistics | 2018 |
| N & L Emporium Ltd | Wholesale & retail | 2024 |
| N a Development Ltd | Information & communication | 2013 |
| N and J Estates Ltd | Real estate | 2024 |
| N Armstrong Fleet Services Ltd | Wholesale & retail | 2025 |
| N B Farm Ltd | Agriculture & fishing | 2025 |
| N B Lancaster + Co | Professional & scientific | 2014 |
| N Dixon & Sons (Demolition) Limited | Construction | 2007 |
| N Hewetson Contracting Ltd | Other services | 2020 |
| N J Dalgliesh Ltd | Wholesale & retail | 2020 |
| N M Windows Limited | Administrative & support | 2014 |
| N R Properties Limited | Real estate | 2025 |
| N S Build Limited | Construction | 2016 |
| NA Combrink Properties Limited | Real estate | 2023 |
| NAD Services Ltd | Transport & logistics | 2023 |