| O.B.M. Retail Ltd | Wholesale & retail | 2026 |
| Oak Electrotechnical Ltd | Construction | 2016 |
| Oakerside Developments Ltd | Construction | 2025 |
| Oakeshott Professional Services Ltd | Construction | 2024 |
| Oakwade Limited | Professional & scientific | 1983 |
| Oakwell Healthcare Ltd | Administrative & support | 2025 |
| Oanderson Off-Shore Services Ltd | Construction | 2023 |
| Octopus Logistics Limited | Transport & logistics | 2023 |
| Odin Art Limited | Professional & scientific | 2012 |
| Ofab Homes Ltd | Real estate | 2026 |
| Ogosta Limited | Health & social care | 2025 |
| OK Recruitment Consultancy Ltd | Professional & scientific | 2020 |
| Olarak Ltd | Financial services | 2020 |
| Olaviol Limited | Professional & scientific | 2016 |
| Old Bond Limited | Wholesale & retail | 1999 |
| Olive Branch Garden Design Limited | Administrative & support | 2012 |
| Olivia & Grey Ltd | Wholesale & retail | 2018 |
| Olley (NE) Limited | Wholesale & retail | 2013 |
| Olpha Limited | Professional & scientific | 2015 |
| Olympus Nails Ltd | Wholesale & retail | 2019 |
| Omazing Limited | Manufacturing | 2026 |
| ON Point Pro Limited | Professional & scientific | 2020 |
| ON the Edge Film Ltd | Information & communication | 2026 |
| One Mcpartlin Limited | Professional & scientific | 2016 |
| One Padel (Hartlepool) Limited | Arts & recreation | 2025 |
| One Padel Limited | Arts & recreation | 2024 |
| One Prep Ltd | Hospitality | 2024 |
| One Stop Build Ltd | Construction | 2025 |
| Onyx Accountancy Limited | Professional & scientific | 2017 |
| Onyx Logistics Limited | Professional & scientific | 2020 |
| Opal FLY Writing Limited | Administrative & support | 2024 |
| Opal Living NE Limited | Professional & scientific | 2017 |
| Operational and Technical Solutions Limited | Professional & scientific | 2004 |
| Optimata Ltd | Transport & logistics | 2023 |
| Options 360 Limited | Education | 2015 |
| Optitek Ltd | Construction | 2023 |
| Optomise Consulting Limited | Professional & scientific | 2014 |
| Opulent Seasons Ltd | Administrative & support | 2025 |
| Opus Instrumentation Ltd | Professional & scientific | 2020 |
| Orangebox Commercial Properties Limited | Households | 2023 |
| Orangebox Properties Limited | Real estate | 2023 |
| Orchard Green Ltd | Transport & logistics | 2015 |
| Orchard Roofing & Building Group Limited | Construction | 2017 |
| Orchard Roofing & Building Ltd | Construction | 2010 |
| ORD Office Limited | Manufacturing | 2014 |
| ORD Services Limited | Professional & scientific | 2023 |
| Organic Orbit Ltd | Professional & scientific | 2025 |
| Origin Planning Services Ltd | Administrative & support | 2019 |
| Original Homes Ltd | Real estate | 2020 |
| Origma Global Services Ltd | Transport & logistics | 2011 |
| Ormex Ltd | Real estate | 2019 |
| Ornament Spot Ltd | Wholesale & retail | 2025 |
| Orphic Models Ltd | Other services | 2020 |
| Orphicstream Ltd | Information & communication | 2020 |
| ORS Contracting Limited | Construction | 1994 |
| Oryx Engineering Solutions Ltd | Professional & scientific | 2024 |
| Oryx Properties Ltd | Real estate | 2018 |
| Osmium Systems Limited | Information & communication | 2024 |
| OT Rehab North East Limited | Health & social care | 2021 |
| OTR Electrical Limited | Manufacturing | 2024 |
| Ourklub Limited | Wholesale & retail | 2025 |
| Owen Twidale Ltd | Professional & scientific | 2026 |
| Owens Security Consultancy Ltd | Construction | 2024 |
| Owners Unity Ltd | Information & communication | 2021 |
| Owton Manor Social Club CIC | Hospitality | 2013 |
| Owton Rossmere CIC | Other services | 2024 |
| P & H Property Developments Ltd | Real estate | 2021 |
| P & N Engineering Ltd | Professional & scientific | 2017 |
| P Hill Comms Ltd | Other services | 2022 |
| P Proudlock Builders Limited | Construction | 2025 |
| P Theasby Ltd | Professional & scientific | 2015 |
| P&C Catering Ltd | Hospitality | 2026 |
| P.B. Welding Inspection Limited | Professional & scientific | 2014 |
| P.J Welding Services Ltd | Other services | 2017 |
| P.R. Professional Salon Supplies Limited | Wholesale & retail | 2007 |
| Paddys Pets Feed Supplies Limited | Wholesale & retail | 2025 |
| Padel IS Life Clubs Ltd | Arts & recreation | 2025 |
| PAG Estates Limited | Real estate | 2018 |
| Pallai Ltd | Wholesale & retail | 2024 |
| Palmer HSE Limited | Health & social care | 2014 |
| Pam&Roh Limited | Hospitality | 2026 |
| Pandacorby Limited | Construction | 2025 |
| Paragon Legal Consultancy Ltd | Professional & scientific | 2006 |
| Park Road Garage Services Ltd | Wholesale & retail | 2019 |
| Parker Ward Consultancy Ltd | Construction | 2021 |
| Parks Interiors (Northern) Limited | Wholesale & retail | 2018 |
| Parkview Lettings Limited | Real estate | 2017 |
| Parkys Global Service & Maintenance Ltd | Agriculture & fishing | 2024 |
| Parshwa Healthcare Limited | Health & social care | 2024 |
| Partyear Limited | Professional & scientific | 2007 |
| Pasegy Limited | Professional & scientific | 2022 |
| Pathway Business Solutions Limited | Professional & scientific | 2025 |
| Patient Services C.I.C. | Health & social care | 2020 |
| Paul Copeman Limited | Construction | 2006 |
| Paul Donkin Coatings Plus Inspection Services Ltd | Other services | 2017 |
| Paul Gooding Technical Services Limited | Construction | 2014 |
| Paul Gough Holdings Ltd | Financial services | 2017 |
| Paul Gough Physio Rooms Limited | Health & social care | 2007 |
| Paul Harbottle Ltd. | Professional & scientific | 2010 |
| Paul Rayner Ltd | Hospitality | 2023 |