| MIA Witham Limited | Wholesale & retail | 2024 |
| Michael Cook Law Firm Limited | Other services | 2019 |
| Michaela Jane Ltd | Education | 2023 |
| Midas Island Capital Limited | Financial services | 2025 |
| Middle East Traditional Barber Ltd | Other services | 2022 |
| Millennia Retail Ltd | Wholesale & retail | 2025 |
| Minworth Limited | Construction | 2025 |
| MK Motors Seaham Limited | Wholesale & retail | 2026 |
| MN Brickwork Ltd | Construction | 2020 |
| Mobile Plant Rooms Limited | Administrative & support | 2017 |
| Mobile WOK Chinese Ltd | Hospitality | 2025 |
| Moga Daniel Ltd | Construction | 2021 |
| Mooshki Ltd | Wholesale & retail | 2012 |
| Morph Engineering Limited | Information & communication | 2019 |
| MORTAR-4-U Limited | Construction | 2020 |
| Morton Construction Ltd | Construction | 2025 |
| MT Designs 360 Ltd | Manufacturing | 2020 |
| Mufasa Gourmet Ltd | Hospitality | 2024 |
| Multi Task Operatives Limited | Construction | 2000 |
| Multi Task Properties Ltd | Real estate | 2017 |
| Multi Task Scaffolding Limited | Extraterritorial | 2010 |
| Murton Food Limited | Hospitality | 2025 |
| Murton Fortune Limited | Hospitality | 2023 |
| Murton Star Nails Ltd | Other services | 2026 |
| MW Motoring Ltd | Wholesale & retail | 2023 |
| Nala Engineers Limited | Construction | 1992 |
| Namaste Seaham Ltd | Hospitality | 2026 |
| NAS Business Services Ltd | Information & communication | 2014 |
| Nature's Embrace Limited | Hospitality | 2023 |
| NCL Inspections Ltd | Other services | 2020 |
| NE Shot Blasters & Sprayers Ltd | Construction | 2025 |
| Neemt Ltd | Transport & logistics | 2026 |
| Neocortex Ltd | Wholesale & retail | 2023 |
| New Happy Eating Takeaway Ltd | Hospitality | 2025 |
| New Seaham Academy | Education | 2012 |
| Newcastle North East Car Recovery Limited | Transport & logistics | 2025 |
| NHK Lettings Ltd | Real estate | 2019 |
| Nice Pint Limited | Wholesale & retail | 1999 |
| Niku Utilities Ltd | Construction | 2023 |
| Niru Brothers Limited | Wholesale & retail | 2015 |
| Niru Convenience Store Ltd | Wholesale & retail | 2022 |
| NKP Transport Ltd | Transport & logistics | 2024 |
| Noblebrim Limited | Hospitality | 1994 |
| North East Bifolds Ltd | Manufacturing | 2016 |
| North East Windtek Limited | Energy | 2023 |
| North Harbour Developments Ltd | Real estate | 2025 |
| North Terrace Ltd | Hospitality | 2023 |
| Northern Sky Motor Cars Ltd | Wholesale & retail | 2016 |
| Northern Sky Properties Ltd | Real estate | 2019 |
| Northumberland Coastal Retreats Limited | Hospitality | 2018 |
| NOT a LIE Delicacies Ltd | Hospitality | 2026 |
| Novo Cabelo Limited | Wholesale & retail | 2019 |
| Nurture Aesthetics Ltd | Other services | 2025 |
| Oakleafe Holdings Ltd | Real estate | 2022 |
| Oakleafe Properties Limited | Real estate | 2015 |
| Odin Construction Services Ltd | Construction | 2025 |
| Odin Guidance Ltd | Manufacturing | 2018 |
| Odin Services Ltd. | Professional & scientific | 2016 |
| Office Glass Partitions Northern Limited | Construction | 2015 |
| Old Vicarage Hetton (Management) Limited | Real estate | 2023 |
| ON the Money Education Ltd | Information & communication | 2025 |
| One Call Engineering Limited | Manufacturing | 2007 |
| Open Air Education Limited | Education | 2024 |
| Oregano Tehran 20 Ltd | Hospitality | 2026 |
| Oyster Property Partners Ltd | Real estate | 2026 |
| P & P Landscapes Limited | Administrative & support | 2006 |
| P Cahill Limited | Wholesale & retail | 2014 |
| P P Heating Ltd | Construction | 2024 |
| P3J Consultancy Ltd | Professional & scientific | 2010 |
| Parade Square Pickles Ltd | Information & communication | 2023 |
| Pari Real Estate Ltd | Real estate | 2022 |
| Park Castle Homes Ltd | Construction | 2025 |
| Parker Clarke Group Ltd | Manufacturing | 2026 |
| Parkview Lipo Clinic Ltd | Other services | 2016 |
| Paul WYN Griffin Limited | Information & communication | 2019 |
| Pegasus Maintenance and Repair Limited | Administrative & support | 2025 |
| Phalanx Communications Ltd | Administrative & support | 2017 |
| Phoebe Lareine Ltd | Arts & recreation | 2025 |
| Phoenix Body and Paint Ltd | Wholesale & retail | 2010 |
| Pink Nails Spa and Beauty Ltd | Other services | 2024 |
| Pioneer W C S Limited | Administrative & support | 2024 |
| Pizza Hot Seaham Ltd | Hospitality | 2022 |
| PJL Services Ltd | Professional & scientific | 2014 |
| PK OFF Licence Ltd | Wholesale & retail | 2026 |
| Playdates CIC | Arts & recreation | 2019 |
| Playology Limited | Education | 2019 |
| Plumbing,Heating and Drainage Solutions Ltd | Energy | 2022 |
| Popinos Seaham Limited | Wholesale & retail | 2019 |
| PR Property North East Ltd | Real estate | 2020 |
| Precision Jetwashing Ltd | Administrative & support | 2026 |
| Premium Timing Limited | Arts & recreation | 2014 |
| Prima Cheese Limited | Wholesale & retail | 2003 |
| Prima Futures Limited | Professional & scientific | 2023 |
| Prima Projects Limited | Real estate | 2023 |
| Pritz Beauty Services Limited | Other services | 2024 |
| Professional Cleaning Services Tyne and Wear Ltd | Administrative & support | 2023 |
| Project SR7 ABC CIC | Arts & recreation | 2025 |
| Properties With Ease Ltd | Real estate | 2026 |
| Property Management by AL Limited | Households | 2025 |
| PS Property Rentals Ltd | Real estate | 2021 |