| Mollisaa Ltd | Health & social care | 2016 |
| Mollisaa Property Ltd | Real estate | 2025 |
| Monairit Properties Limited | Real estate | 1964 |
| Monarch Roofing & Building Ltd | Construction | 2025 |
| Montgomery Blue Limited | Financial services | 2015 |
| Monument Coffee Roasters Limited | Manufacturing | 2026 |
| Morley Building Contractors Limited | Construction | 2013 |
| Morrell Medical Ltd | Health & social care | 2025 |
| Morris Family Partnership LLP | | 2022 |
| Mortgage Advice Service (Tees) Ltd | Financial services | 2024 |
| Morton Park Motor Company (North East) Limited | Wholesale & retail | 2022 |
| Motech Consultancy Ltd | Information & communication | 2015 |
| Motech Digital Ltd | Information & communication | 2025 |
| Motech Group Ltd | Information & communication | 2025 |
| Motech Recruitment Ltd | Administrative & support | 2025 |
| Mound to Ground Limited | Construction | 2023 |
| Mountlion Ltd | Wholesale & retail | 2026 |
| Mountstewart Accountants (Gateshead) Limited | Professional & scientific | 2016 |
| Mountstewart Accountants (Ilkley) Limited | Professional & scientific | 2018 |
| Mountstewart Accountants (Outsourcing) Limited | Professional & scientific | 2018 |
| Mountstewart Accountants (Peterlee) Limited | Professional & scientific | 2018 |
| Mountstewart Accountants (Redcar) Limited | Professional & scientific | 2017 |
| Mountstewart Accountants (Sedgefield) Limited | Professional & scientific | 2015 |
| Mountstewart Accountants (ST Albans) Limited | Professional & scientific | 2018 |
| Moxon Family Partnership LLP | | 2017 |
| MP Devlin QS Services Ltd. | Professional & scientific | 2011 |
| MPM Inspection Services Limited | Administrative & support | 2012 |
| Mprld Investments Ltd | Real estate | 2021 |
| MQI Healthcare Ltd | Health & social care | 2026 |
| MR Moos Family Butchers Limited | Wholesale & retail | 2006 |
| Mrkiyt Limited | Information & communication | 2023 |
| MSH Solutions Limited | Construction | 2004 |
| MTH Rigging Services Ltd | Manufacturing | 2024 |
| MTI Healthcare Ltd | Health & social care | 2022 |
| Mtrkay Limited | Professional & scientific | 2017 |
| Multi Discipline Solutions Limited | Construction | 2003 |
| Mumtaz Ahmed House Limited | Real estate | 2024 |
| Munchies (NE) Ltd | Hospitality | 2024 |
| Munro Family Partnership LLP | | 2019 |
| Musgrave Capital Limited | Construction | 2023 |
| My Fluid Management Services Limited | Professional & scientific | 2019 |
| Mysore Limited | Real estate | 2020 |
| Mysore Partnership LLP | | 2020 |
| N Aitken WP Ltd | Administrative & support | 2024 |
| N Billie Aesthetics Ltd | Health & social care | 2021 |
| N E Shoes Ltd | Wholesale & retail | 2024 |
| N Harvey WP Ltd | Administrative & support | 2024 |
| N Pope & C Bauer WP Ltd | Administrative & support | 2024 |
| N Walker WP Ltd | Administrative & support | 2024 |
| N&C Investments (North East) Ltd | Professional & scientific | 2013 |
| N&N Malik Ltd | Health & social care | 2020 |
| N&N Malik Property Ltd | Real estate | 2024 |
| N&V Holdings Limited | Real estate | 2019 |
| N. K. Brocklehurst Properties Ltd | Real estate | 2016 |
| Nafeesa and Yusuf Ltd | Health & social care | 2026 |
| Nailed IT Academy Ltd | Education | 2020 |
| Napolita Pizza NE Ltd | Hospitality | 2025 |
| Nariman Plumbing and Heating Ltd | Construction | 2021 |
| Narinspire Ltd | Health & social care | 2023 |
| Narmadanand Properties Ltd | Real estate | 2026 |
| Naseem Medical Service Limited | Health & social care | 2023 |
| Nash's Farm Ltd | Real estate | 2025 |
| Nathen Framework Ltd | Real estate | 2025 |
| National Numbers Limited | Wholesale & retail | 1997 |
| Nationwide Healthcare Limited | Health & social care | 2004 |
| Nayak Medics Limited | Health & social care | 2024 |
| NB Aesthetics Training Academy Ltd | Health & social care | 2023 |
| NB Ecommerce & Design Ltd | Information & communication | 2022 |
| NB Rentals (NE) Ltd | Households | 2025 |
| NBC Family Holdings Limited | Real estate | 2018 |
| NBC Family Partnership LLP | | 2018 |
| NBC Management Ltd | Real estate | 2012 |
| NBZ Cleaning Ltd | Administrative & support | 2025 |
| Ncube Family LLP | | 2021 |
| ND Lettings Ltd | Real estate | 2019 |
| ND Property Group Ltd | Real estate | 2019 |
| NDK Patel Family Holdings Ltd | Real estate | 2020 |
| NDK Patel Family Partnership LLP | | 2020 |
| NE Refurb Ltd | Construction | 2025 |
| Need the Greens Limited | Wholesale & retail | 2022 |
| Nelvek Limited | Wholesale & retail | 2002 |
| NEM Property Solutions Ltd | Real estate | 2023 |
| Nemm Offshore Ltd | Administrative & support | 2025 |
| Nems Market Research Limited | Professional & scientific | 2000 |
| Nene Events Ltd | Arts & recreation | 2022 |
| NEO Biomed Services Ltd | Health & social care | 2017 |
| Neotech Consulting Limited | Information & communication | 2014 |
| Neptune Property Partnership LLP | | 2023 |
| Nero Entertainment Ltd | Arts & recreation | 2023 |
| Nesb Services Limited | Transport & logistics | 2024 |
| Nesmo Vehicle Conversions Ltd | Manufacturing | 2020 |
| Network Notwork CIC | Information & communication | 2024 |
| Networked Housing Limited | Real estate | 2013 |
| Neure Health Limited | Health & social care | 2024 |
| Neuroscience Clinic Ltd | Health & social care | 2022 |
| Nevison Smokehouse & Cafe Ltd | Hospitality | 2025 |
| New Chung Ying Limited | Hospitality | 2023 |
| New Lane Management Ltd | Households | 2020 |
| New Life Church, Teesside | Health & social care | 2012 |
| New Road Surfacing Limited | Other services | 2019 |