| Northumbrian Homes Limited | Construction | 2021 |
| Northumbrian Soul UK Ltd | Other services | 2026 |
| Northumbrian TIN Soldier Limited | Manufacturing | 2017 |
| Northumbriana Ltd | Information & communication | 2023 |
| Novagonzales Ltd | Health & social care | 2023 |
| Novumcore Limited | Professional & scientific | 2025 |
| NRS Dynamics Ltd | Professional & scientific | 2023 |
| NS Access Ltd | Construction | 2015 |
| NS Accountancy (North East) Ltd | Professional & scientific | 2016 |
| NS Metro Limited | Hospitality | 2025 |
| Nsjrenew Ltd | Construction | 2025 |
| Nsvn the Label Ltd | Wholesale & retail | 2025 |
| NT Taxi Hire Limited | Administrative & support | 2024 |
| NU Access Ltd | Construction | 2024 |
| Nucas Managed Legal Services Limited | Professional & scientific | 2025 |
| Nusa Ltd | Other services | 2024 |
| NVB (North East) Limited | Hospitality | 2004 |
| O.P. Investments Ltd | Real estate | 2019 |
| Oakenclough Buildings Limited | Construction | 2004 |
| Oakeys Safety Ltd | Wholesale & retail | 2022 |
| Oakfield Grange Limited | Professional & scientific | 1999 |
| Oakline Ltd | Wholesale & retail | 2025 |
| Oakum Marine Ltd | Manufacturing | 2021 |
| OAN CLO Ltd | Wholesale & retail | 2025 |
| OB Group One Ltd | Hospitality | 2024 |
| Obair Mara Ltd | Agriculture & fishing | 2026 |
| Objectspaces Ltd | Information & communication | 2016 |
| Obla UK | Education | 2017 |
| Ocean Current Cables Consultancy Limited | Administrative & support | 2014 |
| Ocean Flow Energy Ltd | Professional & scientific | 2001 |
| Oceanonlinestore Limited | Manufacturing | 2018 |
| OD Consulting Limited | Professional & scientific | 2019 |
| Oddballs Apparel Limited | Wholesale & retail | 2014 |
| Oddballs Holdings Limited | Financial services | 2019 |
| OFD Services Limited | Professional & scientific | 2025 |
| OFF the MAP Developments Ltd | Construction | 2024 |
| Officernd Limited | Professional & scientific | 2015 |
| OH Renewables Limited | Manufacturing | 2023 |
| Oliva-Bolam Properties Limited | Hospitality | 2024 |
| Olive & Bean Limited | Hospitality | 2012 |
| Olive Baum Ltd | Real estate | 2021 |
| Oliver & Lynch Limited | Information & communication | 2017 |
| Olsps Holdings Ltd | Administrative & support | 2011 |
| Omuka Limited | Real estate | 2025 |
| ON Electrification Limited | Professional & scientific | 2024 |
| ON the Podium Limited | Professional & scientific | 2025 |
| ON the Tyne Limited | Real estate | 2023 |
| One Design Group Ltd | Information & communication | 2026 |
| One I.T. Support Ltd | Information & communication | 2011 |
| Oneworld Knowledge Academy Limited | Education | 2022 |
| Onthetyneproperty Limited | Real estate | 2025 |
| Onyx Industries Ltd | Arts & recreation | 2024 |
| Open IOT Limited | Information & communication | 2018 |
| Operation Code Ltd | Professional & scientific | 2024 |
| Optima Blinds & Shutters Ltd | Other services | 2026 |
| Optimise Neurotherapy Centre Limited | Health & social care | 2010 |
| Optimum Flooring Solutions Limited | Wholesale & retail | 2019 |
| Oracle Housing Solutions Limited | Real estate | 2025 |
| Orbis Support EOT Limited | Other services | 2024 |
| Orbis Support Limited | Health & social care | 2015 |
| Orca Investments Global Limited | Construction | 2011 |
| Orca Steel UK Limited | Construction | 2023 |
| ORD Engineering Services Ltd | Professional & scientific | 2025 |
| Orrock Investments Ltd | Real estate | 2023 |
| Orrock Property Holdings Ltd | Real estate | 2024 |
| Orrock Property Lettings Ltd | Real estate | 2024 |
| Orrock Property Ltd | Real estate | 2022 |
| Osborne Orthodontics Ltd | Health & social care | 2007 |
| Ostfeld Limited | Real estate | 1991 |
| OTB E-Commerce Limited | Information & communication | 2025 |
| OTT Property Ltd | Real estate | 2013 |
| Outdoor Publishing Limited | Information & communication | 2018 |
| Outlined Solutions Limited | Administrative & support | 2014 |
| Outright Limited | Other services | 2016 |
| Ovaller Limited | Wholesale & retail | 2026 |
| Owen Robertson Architects Ltd | Professional & scientific | 2024 |
| Owston Commercials Limited | Wholesale & retail | 2005 |
| Ozbell Ltd | Real estate | 2023 |
| P C (North Shields) Ltd | Hospitality | 2021 |
| P C (Tyne & Wear) Ltd | Hospitality | 2025 |
| P Ellis Services Ltd | Other services | 2025 |
| P Herdman Heating Services Ltd | Administrative & support | 2017 |
| P Plunkett & Sons Limited | Financial services | 2015 |
| P Sekta Ltd | Wholesale & retail | 2024 |
| P.P Listings Ltd | Real estate | 2026 |
| Pace Accountancy (Northern) Ltd | Professional & scientific | 2024 |
| Pace Retail Ltd | Wholesale & retail | 2021 |
| Palace of Science CIC | Education | 2020 |
| Pale Fountain Ltd | Administrative & support | 2022 |
| Pamray Property Company Limited | Real estate | 1951 |
| Panel Solutions Limited | Manufacturing | 2017 |
| Paradice Productions Ltd | Information & communication | 2022 |
| Paramount Home Improvements (N.E) Ltd | Construction | 2023 |
| Paramount Verandas Ltd | Construction | 2025 |
| Parker and Sons Electrical Ltd | Construction | 2015 |
| Parker Clothing Limited | Wholesale & retail | 2024 |
| Parkside Care Limited | Health & social care | 2008 |
| Parkside Hand & Wrist Ltd | Health & social care | 2024 |
| Parmley Technologies Limited | Manufacturing | 2000 |
| Party S R US Limited | Administrative & support | 2012 |