| M & VB Estates LLP | | 2021 |
| M a Driving School Yorkshire Ltd | Education | 2024 |
| M a Mechanical Services Limited | Professional & scientific | 2023 |
| M a W Scaffolding Limited | Construction | 2025 |
| M B Distribution (Cleveland) Limited | Wholesale & retail | 1987 |
| M Chapman Ltd | Professional & scientific | 2024 |
| M D Tech Services Ltd | Construction | 2008 |
| M F Wind Turbines Ltd | Professional & scientific | 2025 |
| M Holmes Solutions Ltd | Construction | 2017 |
| M J Family Homes Limited | Real estate | 2021 |
| M J S Services Limited | Professional & scientific | 2008 |
| M Judge Services Ltd | Construction | 2009 |
| M Khan Enterprises Limited | Real estate | 2025 |
| M Lofthouse Ltd | Real estate | 2020 |
| M N Bartlett Properties Ltd | Real estate | 2021 |
| M S Infrastructure Ltd | Construction | 2026 |
| M S Khan Consultancy Ltd | Health & social care | 2014 |
| M Shutt Engineering Ltd | Construction | 2014 |
| M T W Rigging & Lifting Limited | Mining & quarrying | 2016 |
| M W C Services Limited | Other services | 2003 |
| M Watson Decorators Ltd | Construction | 2019 |
| M Willis Accountancy Services Ltd. | Professional & scientific | 2016 |
| M Wilson Planning Ltd | Professional & scientific | 2026 |
| M&A Property Partners Limited | Real estate | 2025 |
| M&B Communications Limited | Information & communication | 2020 |
| M&B Properties NE Limited | Real estate | 2017 |
| M&E Cleaning Limited | Transport & logistics | 2021 |
| M&G 13 Solutions Ltd | Professional & scientific | 2016 |
| M&G Security Limited | Administrative & support | 2022 |
| M&J Health & Safety Solutions Ltd | Administrative & support | 2024 |
| M&L Renewables (North East) Ltd | Other services | 2023 |
| M&M Adas Ltd | Wholesale & retail | 2022 |
| M&M HSE Consultancy Services Ltd | Construction | 2025 |
| M&M Richardson Mechanical Ltd | Construction | 2025 |
| M&M Rigging Services Limited | Professional & scientific | 2018 |
| M&M Tyres (NE) Ltd | Wholesale & retail | 2016 |
| M&Rp (Teesside) Limited | Administrative & support | 2019 |
| M-Energy Ltd | Information & communication | 2024 |
| M-Hayes Ltd | Manufacturing | 2025 |
| M. H. Petch Limited | Agriculture & fishing | 1984 |
| M.A North East Ltd | Professional & scientific | 2024 |
| M.A. Enterprises Limited | Arts & recreation | 1992 |
| M.A. Industrial Services Ltd. | Professional & scientific | 2014 |
| M.A.H. Inspection Services Limited | Professional & scientific | 2017 |
| M.A.N Coating & Insulation Consultants Limited | Professional & scientific | 2024 |
| M.Downing Limited | Construction | 2024 |
| M.F.Raza.Uk Limited | Wholesale & retail | 2022 |
| M.H.L.R Services Ltd | Construction | 2024 |
| M.J. Goldspink Limited | Administrative & support | 2001 |
| M.J. Potts (Designs) Limited | Professional & scientific | 1989 |
| M.Pinkney C & I Consultants Ltd | Administrative & support | 2007 |
| M.R.O Property Developments Ltd | Real estate | 2024 |
| M.T. Lucas Contracting Limited | Administrative & support | 2023 |
| M1 (TE) Car Sales Limited | Wholesale & retail | 2025 |
| M2SA UK Limited | Wholesale & retail | 2025 |
| M3L Engineering Ltd | Professional & scientific | 2018 |
| M7 MNK Limited | Professional & scientific | 2007 |
| MA Hospitality Group Ltd | Wholesale & retail | 2016 |
| MA Jacob Estates Ltd | Real estate | 2025 |
| MA Jacob’S Renovations Ltd | Construction | 2025 |
| MA Mini Market Ltd | Wholesale & retail | 2023 |
| MA Payroll Consultancy Ltd | Professional & scientific | 2025 |
| MA Tulceanu Logistics Limited | Transport & logistics | 2025 |
| Maas Automation Services Ltd | Information & communication | 2018 |
| Maaz Solutions Ltd | Other services | 2022 |
| MAB Neill Ltd | Professional & scientific | 2017 |
| Mabo Media Ltd | Professional & scientific | 2013 |
| Mabsafety Limited | Construction | 2025 |
| MAC Estates (NE) Limited | Real estate | 2010 |
| MAC Signs (NE) Limited | Manufacturing | 2015 |
| Macauley Andrew Fenton Limited | Construction | 2021 |
| Machine Works Capital Ltd | Real estate | 2023 |
| Mackcj Ltd | Wholesale & retail | 2019 |
| Mackenzie Clinical Consulting Ltd | Information & communication | 2011 |
| Macmillan Motor Company Limited | Wholesale & retail | 2012 |
| Macy Brown Ltd | Hospitality | 2014 |
| Madalin Duman Logistics Limited | Transport & logistics | 2025 |
| Made by Creatives Ltd | Information & communication | 2017 |
| Mafc Inspection Ltd | Professional & scientific | 2023 |
| MAG & K. Cleaning Services Ltd | Administrative & support | 2024 |
| Magic Ritmo Ltd | Information & communication | 2024 |
| Magnetar (NE) Limited | Professional & scientific | 2016 |
| Magnificent Motors Limited | Wholesale & retail | 2020 |
| Magnihomes Limited | Real estate | 2023 |
| Magnum Properties (NE) Limited | Real estate | 2013 |
| Magureanumr Ltd | Transport & logistics | 2022 |
| Maharaja Tandoori M Ltd | Hospitality | 2025 |
| Maharban Khan Rental Limited | Transport & logistics | 2014 |
| Mahesh Foods Ltd | Hospitality | 2026 |
| Mahkato L.P. | | 2020 |
| Mahmood & Sons Butchers Limited | Wholesale & retail | 2016 |
| Maholaat Limited | Wholesale & retail | 2021 |
| Mailorder Ltd | Wholesale & retail | 2025 |
| Main - Taking Autism Personally | Education | 2003 |
| Maine Property Development Limited | Construction | 2025 |
| MAINTENANCE365(UK) Ltd | Construction | 2024 |
| Maisav Projects Limited | Construction | 2023 |
| Majestic Innovations Ltd | Professional & scientific | 2025 |
| Majestic Roofing Ltd | Construction | 2021 |
| Majors Manor Ltd | Arts & recreation | 2026 |