| LS Luxe Cleaning Ltd | Administrative & support | 2025 |
| LS One Properties Ltd | Real estate | 2019 |
| LS Surveying Limited | Construction | 2014 |
| LT Connect Ltd | Information & communication | 2025 |
| LTS Lifting Turnaround Limited | Professional & scientific | 2023 |
| Lubri-Technologies Limited | Administrative & support | 2016 |
| Lucian Optics Ltd | Construction | 2016 |
| Lucy M Carter Ltd | Professional & scientific | 2024 |
| Luhal Holdings Limited | Financial services | 2025 |
| Luke French Coatings Limited | Construction | 2010 |
| Luke Hand Electricals Limited | Construction | 2022 |
| Luna Tech Consulting Limited | Professional & scientific | 2019 |
| Lunar Techs Ltd | Construction | 2011 |
| Lust Home Ltd | Extraterritorial | 2021 |
| Luxe Labels Clothing Limited | Wholesale & retail | 2024 |
| Luxury Resort DJS Limited | Arts & recreation | 2019 |
| Lvmt Properties Ltd | Real estate | 2018 |
| LW Environmental Ltd | Extraterritorial | 2025 |
| LW Joinery & Kitchens Ltd | Construction | 2024 |
| LW Repairs Limited | Construction | 2025 |
| Lwtelecoms Limited | Information & communication | 2015 |
| Lyla Belle's Ltd | Hospitality | 2019 |
| LZR Welding Ltd | Manufacturing | 2016 |
| M & H Joinery (N.E) Limited | Manufacturing | 2024 |
| M & S Parmo Limited | Wholesale & retail | 2024 |
| M D Electech Services Limited | Construction | 2015 |
| M J Giles Limited | Education | 2025 |
| M P N Proserve Ltd | Administrative & support | 2007 |
| M T Mortar Ltd | Manufacturing | 2023 |
| M&I H Ltd | Other services | 2025 |
| M&L Procomp Ltd | Professional & scientific | 2022 |
| M&T Property Partners Solutions Limited | Real estate | 2025 |
| M.A.G. Pipelines Limited | Construction | 2012 |
| M.Wallis Instrument Consulting Ltd | Professional & scientific | 2022 |
| M6 Engineering Ltd | Professional & scientific | 2024 |
| Mabella Hair Co Ltd | Other services | 2025 |
| MAC Contracting Group Ltd. | Construction | 2022 |
| Macg Consultancy Limited | Arts & recreation | 2019 |
| Mackenzie Scaffolding Limited | Construction | 2007 |
| Macs Fabs Ltd | Manufacturing | 2019 |
| Macwes Ltd | Manufacturing | 2021 |
| Maddison Planning Ltd | Professional & scientific | 2025 |
| Made by Mariella Limited | Other services | 2024 |
| Made Compliance Ltd | Professional & scientific | 2025 |
| Madlinc Property Ltd | Real estate | 2025 |
| Madon Plant Training Ltd | Education | 2021 |
| MAG Elwick Ltd | Professional & scientific | 2024 |
| MAG Flow Limited | Wholesale & retail | 2025 |
| Magic T Cleaning Services Ltd | Administrative & support | 2025 |
| Magpie Support C.I.C. | Other services | 2024 |
| Magpie Support Services Ltd | Other services | 2023 |
| Maha IT Group Ltd | Information & communication | 2025 |
| Mahal Teeside Ltd | Hospitality | 2026 |
| Maiden Offshore Services Ltd | Professional & scientific | 2014 |
| Maiden Property Services Limited | Real estate | 2020 |
| Mains Electrical Distributors Limited | Wholesale & retail | 1998 |
| Maizeweld Services Ltd | Construction | 2024 |
| Majorfield Assets Limited | Real estate | 2025 |
| Majorfield Limited | Real estate | 2025 |
| Make a Drink Ltd | Real estate | 2026 |
| Make IT Different | Education | 2019 |
| Making Sense of Limited | Education | 2012 |
| Makola & Beyond Limited | Wholesale & retail | 2024 |
| Makola African Market Ltd | Wholesale & retail | 2024 |
| Mallard Outsourcing Limited | Administrative & support | 2019 |
| Malone Offshore North East Ltd | Construction | 2025 |
| MAM Assets Limited | Real estate | 2022 |
| Mamta 786 Ltd | Hospitality | 2021 |
| Manakia Ltd | Real estate | 2025 |
| Mandelbrot Limited | Professional & scientific | 2021 |
| Mann at Work Traffic Management Limited | Construction | 2025 |
| Manok Cleaning and Removal Services Ltd | Administrative & support | 2025 |
| Manor Farm Investment Properties Limited | Real estate | 2025 |
| Manor Motors Limited | Wholesale & retail | 2007 |
| Manr Enterprise Ltd | Real estate | 2025 |
| Maple Home Care Ltd | Health & social care | 2023 |
| Marco's Italian Bistro Ltd | Hospitality | 2025 |
| Marina Thai Village Ltd | Hospitality | 2019 |
| Marina's Amigos Childcare Ltd | Health & social care | 2024 |
| Marinahartlepool Ltd | Hospitality | 2025 |
| Mariners United Sporting Club CIC | Education | 2025 |
| Marios Pizzeria NE Ltd | Hospitality | 2024 |
| Mariz Engineering Solutions Ltd | Water & waste | 2026 |
| Mariz Solutions Ltd | Professional & scientific | 2022 |
| Mark Leck Property Limited | Real estate | 2020 |
| Mark Lloyd Limited | Wholesale & retail | 2011 |
| Mark Lloyd Properties Limited | Real estate | 2020 |
| Mark Whittingham Engineering Consultants Ltd | Professional & scientific | 2025 |
| Market ME Online Ltd | Professional & scientific | 2016 |
| Marley Financial Limited | Financial services | 2019 |
| Marlwood Financial Group Limited | Financial services | 2020 |
| Marmaris Turkish Barbershop Ltd | Other services | 2024 |
| Marrian Lettings Ltd | Real estate | 2024 |
| Marshall Electech Limited | Construction | 2025 |
| Marshall Tunney Properties Ltd | Real estate | 2025 |
| Martin's Building and Plumbing Ltd | Construction | 2020 |
| Marvellous Meisie Healhcare Ltd | Transport & logistics | 2024 |
| Masala Indian Lounge Limited | Hospitality | 2016 |
| Masala Spice Lounge Ltd | Hospitality | 2022 |
| Masala Tandoori Lounge Ltd | Hospitality | 2025 |