| Mlds Decorating Services Ltd | Construction | 2017 |
| MLK Property Investment Ltd | Real estate | 2020 |
| MLM Homes Limited | Real estate | 2019 |
| MM Groundworks Ltd | Construction | 2023 |
| Mmct Limited | Administrative & support | 2004 |
| MMS Property Lettings Ltd | Real estate | 2023 |
| MN Tiling Solutions Ltd | Construction | 2024 |
| Mo's Properties (NE) Ltd | Information & communication | 2024 |
| Mobile City Limited | Wholesale & retail | 2020 |
| Mobile Healthcare Solutions Limited | Health & social care | 1998 |
| Mobile Shred Limited | Extraterritorial | 2010 |
| Mobile Tech Centre Gateshead Ltd | Other services | 2021 |
| Mobile Tech Gateshead Ltd | Information & communication | 2021 |
| Mobile Tech NE Ltd | Wholesale & retail | 2022 |
| Mobility Direct (North) Holding Limited | Financial services | 2026 |
| Mobility Direct (North) Limited | Wholesale & retail | 2010 |
| Mochy Ltd | Real estate | 2021 |
| Modelfixscenics Limited | Wholesale & retail | 2019 |
| Modern Water Limited | Water & waste | 2006 |
| Modest Technologies Ltd | Administrative & support | 2022 |
| Modular Office and Storage Systems Limited | Manufacturing | 1991 |
| Moglu Ltd | Real estate | 2020 |
| Mogul (NE) Ltd | Wholesale & retail | 2026 |
| Moisdos Yedias Hatoirah Ltd | Health & social care | 2021 |
| Mojo People Limited | Professional & scientific | 2014 |
| MOK Surgery Ltd | Health & social care | 2024 |
| Molafaos Services Limited | Professional & scientific | 2020 |
| Molldan Limited | Real estate | 2023 |
| Momentous Group Ltd | Education | 2020 |
| Momentum B Ltd | Professional & scientific | 2025 |
| Momentum Group NE Limited | Real estate | 2021 |
| MON -Ryan's Limited | Hospitality | 2024 |
| Monoven Ltd | Information & communication | 2024 |
| Monsun Indian Ltd | Hospitality | 2024 |
| Montagu & North Fenham Football Club | Arts & recreation | 2012 |
| Monteiro Fernandes Ltd | Health & social care | 2013 |
| Montreux Consulting Limited | Financial services | 2015 |
| Moolasingh & Sons Ltd | Hospitality | 2023 |
| Mopion Investments Limited | Financial services | 2026 |
| Mordon Hall Property Limited | Real estate | 2025 |
| More Than Dance Community Interest Company | Education | 2006 |
| More Than Words (Marketing) Limited | Professional & scientific | 2016 |
| Morgan Asset Management Limited | Professional & scientific | 2006 |
| Morgan Bernard Limited | Information & communication | 2021 |
| Morgan Family CIC | Health & social care | 2022 |
| Morgan Lonprell Limited | Administrative & support | 1979 |
| Morodeasro 1 Ltd | Real estate | 2026 |
| Morris Electrical Design Services Limited | Professional & scientific | 2014 |
| Mortgage City | | 1991 |
| Mortgages North East Ltd | Financial services | 2020 |
| Mortgages NOW Ltd | Financial services | 2019 |
| Mosphaiti Ltd | Wholesale & retail | 2012 |
| Mostavi Ltd | Health & social care | 2012 |
| Mostech Ltd | Wholesale & retail | 2025 |
| Motif Film Productions Ltd | Information & communication | 2026 |
| Motif Pictures Ltd | Information & communication | 2020 |
| Motor Bodywork Limited | Wholesale & retail | 2022 |
| Motor Nation Cars Limited | Extraterritorial | 2007 |
| Mountain ASH Pharmaceutical Ltd | Health & social care | 2025 |
| Mountsett Ltd | Financial services | 2026 |
| Mouse Cage Events Limited | Administrative & support | 2025 |
| MP Automotive NE Ltd | Wholesale & retail | 2026 |
| MPE Utility Services Ltd | Administrative & support | 2021 |
| MPR Renovation Ltd | Construction | 2026 |
| MR Chippy Darlington Ltd | Wholesale & retail | 2024 |
| MR Grass (Newcastle) Ltd | Administrative & support | 2021 |
| MR H - Outdoor Experiences Ltd | Education | 2020 |
| MR H Nursery Schools Ltd | Health & social care | 2024 |
| MR N'S Burgers and Shakes Ltd | Hospitality | 2025 |
| MR Nitro's Franchise Limited | Administrative & support | 2019 |
| MR Spark Electrical Limited | Construction | 2024 |
| MRC Medics Ltd | Health & social care | 2021 |
| MRP Property Group Ltd | Real estate | 2024 |
| MRS C'S Patisserie Ltd | Wholesale & retail | 2019 |
| MRS May's Bouquets Ltd | Wholesale & retail | 2025 |
| MS Business Intelligence Solutions Limited | Professional & scientific | 2013 |
| MS Security Systems Limited | Administrative & support | 2025 |
| MSA Locums (NE) Ltd | Wholesale & retail | 2025 |
| MSA Restoration (UK) Limited | Professional & scientific | 2004 |
| MSD Investments Ltd | Real estate | 2016 |
| MSF NE Ltd | Wholesale & retail | 2024 |
| MSF Upholstery Ltd | Manufacturing | 2018 |
| MSG Joinery Ltd | Construction | 2024 |
| MSH Waste Solutions Ltd | Transport & logistics | 2017 |
| Mshdrawingservices Ltd | Professional & scientific | 2019 |
| Msjv Ltd | Real estate | 2024 |
| MSM Convenience Limited | Wholesale & retail | 2020 |
| MSR Electrical Services Ltd | Administrative & support | 2016 |
| Mssl (GB) Limited | Manufacturing | 2004 |
| Mstmoffshore Ltd | Energy | 2025 |
| MSU Furniture Ltd | Manufacturing | 2022 |
| MT Brickwork Services Ltd | Construction | 2022 |
| MT Golide Limited | Real estate | 2015 |
| MTF (North East) Limited | Administrative & support | 2022 |
| MTH Integrated Security Ltd | Administrative & support | 2025 |
| MTM Residential Limited | Real estate | 2019 |
| MTM-1 Limited | Administrative & support | 2014 |
| MTR1 Ltd | Wholesale & retail | 2025 |
| MTW Marketing Limited | Professional & scientific | 2025 |
| Mugabe Developments Limited | Transport & logistics | 2025 |