| LOW House Farm Limited | Agriculture & fishing | 2021 |
| LOW Whinnow Limited | Agriculture & fishing | 2016 |
| LOW Wood Dairy Company | Administrative & support | 2009 |
| LP & Co. Property Group Ltd | Real estate | 2025 |
| LR Plastering Cumbria Limited | Construction | 2025 |
| LRG Couriers Ltd | Transport & logistics | 2019 |
| Lrmedia Limited | Wholesale & retail | 2024 |
| LSL Estate Management Limited | Real estate | 2004 |
| LTG Home Improvements Limited | Construction | 2018 |
| Luchico Limited | Real estate | 2025 |
| Lucinda Claude Ltd | Health & social care | 2022 |
| Lucky Date Carlisle Ltd | Hospitality | 2019 |
| Lucky Dragon (Carlisle) Limited | Hospitality | 2014 |
| Lukas W Kitchen Fitter Ltd | Construction | 2022 |
| Lukasz K Logistics Limited | Transport & logistics | 2022 |
| Lumen Industries Limited | Professional & scientific | 2020 |
| Luna Selene Ltd | Wholesale & retail | 2024 |
| Lundie Farming Limited | Agriculture & fishing | 2013 |
| Lune and Fylde Farmers (Holdings) Limited | Financial services | 2017 |
| Luvy Vietfood Ltd | Hospitality | 2023 |
| LUX Tanning Beds Limited | Other services | 2025 |
| Luxe Brows Limited | Other services | 2017 |
| Luxe Flooring (Cumbria) Ltd | Wholesale & retail | 2025 |
| Luxury Living Development Ltd | Real estate | 2016 |
| Lvcourier Ltd | Transport & logistics | 2025 |
| Lydialights Ltd | Real estate | 2024 |
| Lynas Electrical Limited | Construction | 2022 |
| Lyon Group Holdings | Hospitality | 2000 |
| Lyon Leisure Limited | Hospitality | 2020 |
| M & B Body Repairs Limited | Wholesale & retail | 2013 |
| M & K Home Improvements Limited | Construction | 2022 |
| M & L Surgical Services Limited | Health & social care | 2010 |
| M & M Scaffolding (Northern) Limited | Construction | 2007 |
| M & T Wight Ltd | Construction | 2017 |
| M a Bowe Delivery Services Ltd | Transport & logistics | 2024 |
| M a Howes Building Contractors Limited | Construction | 2006 |
| M and L Developments Limited | Construction | 2020 |
| M Aslam Site Services Ltd | Manufacturing | 2019 |
| M Bird Limited | Hospitality | 2009 |
| M Bulman Ltd | Transport & logistics | 2019 |
| M D Engineering Services (Carlisle) Ltd | Construction | 2019 |
| M Electrical Contractors (Leeds) Limited | Construction | 2020 |
| M Forster Building Contractor Limited | Construction | 2015 |
| M G I Associates Limited | Construction | 2019 |
| M Graham Electrical Services Ltd | Manufacturing | 2015 |
| M Group (Cumbria) Ltd | Construction | 2018 |
| M H Electrical (Carlisle) Limited | Construction | 2021 |
| M H Industrial Cleaning Limited | Administrative & support | 2021 |
| M H Paving & Landscapes Ltd | Administrative & support | 2024 |
| M Hartley Limited | Wholesale & retail | 2005 |
| M J Holliday Roofing Limited | Construction | 2021 |
| M Jackson Plastering (Cumbria) Limited | Construction | 2023 |
| M Lightfoot Limited | Extraterritorial | 2021 |
| M Mackenzie Ltd | Transport & logistics | 2014 |
| M Matthews & SON Limited | Construction | 2017 |
| M Miller Trading Ltd | Construction | 2024 |
| M Nicholson Limited | Agriculture & fishing | 2007 |
| M Nolan Limited | Construction | 2023 |
| M R Skelton Services Limited | Administrative & support | 2014 |
| M Raywood Ltd | Agriculture & fishing | 1974 |
| M Tech Auto Engineers Limited | Wholesale & retail | 2011 |
| M Ward Property Services Limited | Real estate | 2017 |
| M Watson Joinery Limited | Construction | 2007 |
| M Welters & Daughters Limited | Administrative & support | 2022 |
| M Wilson Limited | Construction | 2014 |
| M&A Retail Trading Limited | Wholesale & retail | 2025 |
| M&B Windows Limited | Construction | 2006 |
| M&G Cash Ltd | Agriculture & fishing | 2019 |
| M&H Clapperton Civil Engineering Limited | Construction | 2013 |
| M&M Fearon Ltd | Hospitality | 2021 |
| M&M Todd Limited | Transport & logistics | 2017 |
| M&T Decorators Limited | Administrative & support | 2011 |
| M-Tech Electrical Limited | Construction | 2007 |
| M-Unit C.I.C. | Education | 2020 |
| M. Seggie Holdings Ltd | Financial services | 2023 |
| M.J. Telford Garage (Carlisle) Limited | Wholesale & retail | 1974 |
| M.R.H. Minerals (NO 2) Limited | Real estate | 2025 |
| M.R.H.Minerals Limited | Mining & quarrying | 1941 |
| MA and YM Ltd | Health & social care | 2025 |
| Mabel Wood (Great Clifton) Management Company Limited | Households | 2013 |
| Macarthur Agriculture Ltd | Real estate | 2023 |
| Machaul Logistics Ltd | Transport & logistics | 2018 |
| Macpherson Windows Ltd | Construction | 2025 |
| Madbookings Ltd | Administrative & support | 2014 |
| Made in Cumbria Limited | Other services | 2010 |
| Made in Megara Limited | Wholesale & retail | 2007 |
| Madge & FLO Property Limited | Hospitality | 2021 |
| Maggs Construction Ltd | Construction | 2013 |
| Magic Collectables Ltd | Wholesale & retail | 2025 |
| Magic Happy Kitchen Ltd | Hospitality | 2023 |
| Magic Mary’S Ltd | Wholesale & retail | 2026 |
| Magnus Homes Limited | Construction | 2005 |
| Mahaan Limited | Professional & scientific | 2022 |
| Maher TIC Limited | Wholesale & retail | 2023 |
| Maid in Carlisle Ltd | Administrative & support | 2021 |
| MAID2CLEAN (Northern) Limited | Administrative & support | 2013 |
| Mailstork Ltd | Manufacturing | 2019 |
| Mainstreet Snack Shack Ltd | Hospitality | 2024 |
| Maiquez Limited | Hospitality | 2007 |
| Mairi Macintyre (Scottish Sportswear) Limited | Extraterritorial | 1952 |