| Orvexa Ltd | Wholesale & retail | 2025 |
| Orzechowski Logistics Ltd | Transport & logistics | 2014 |
| OSA IT Services Limited | Information & communication | 2014 |
| Osarumhense . M. Olotu Ltd | Health & social care | 2023 |
| Osasco Enterprises Ltd | Health & social care | 2017 |
| Osborne Engineering Solutions Limited | Professional & scientific | 2025 |
| Osborne House Consulting Ltd | Information & communication | 2015 |
| Oscaroscarhotel Limited | Wholesale & retail | 2021 |
| Osemenrity Ltd | Health & social care | 2023 |
| Osgodby Farm Ltd | Agriculture & fishing | 2023 |
| Osier Farm Ltd | Construction | 2019 |
| Oskars Homes Ltd | Real estate | 2022 |
| Oslyn Holdings Limited | Administrative & support | 2020 |
| Osmoof Incorporated Limited | Professional & scientific | 2020 |
| OSS House Service Ltd | Construction | 2018 |
| OSS Integrated Professional Services Limited | Education | 2026 |
| Ostrich Inn Peterborough Limited | Hospitality | 2019 |
| Ostrich Whittlesey Ltd | Hospitality | 2025 |
| OT Hiit Urban Fitness Ltd | Arts & recreation | 2023 |
| OTB Sales & Manufacturing Limited | Manufacturing | 2014 |
| Otiti Limited | Other services | 2019 |
| Otium Global Capital Advisors Ltd | Professional & scientific | 2026 |
| Otium Global Consulting Ltd | Professional & scientific | 2024 |
| OTO Transport Ltd | Transport & logistics | 2024 |
| Otos Holdings Limited | Transport & logistics | 2026 |
| Otos Liverpool Ltd | Real estate | 2026 |
| Otos Slaley Limited | Real estate | 2025 |
| Otrexo Limited | Wholesale & retail | 2018 |
| Otter Developments Limited | Construction | 2021 |
| Otti Care Limited | Health & social care | 2014 |
| Ottoman 1 Ltd | Hospitality | 2019 |
| OTU EWA International Limited | Arts & recreation | 2023 |
| Oundle Autos Ltd. | Wholesale & retail | 2020 |
| Oundle Barber Ltd | Other services | 2019 |
| Oundle Carpets and Flooring Ltd | Manufacturing | 2012 |
| Oundle Clocks Limited | Wholesale & retail | 2005 |
| Oundle Dog Field Limited | Real estate | 2025 |
| Oundle Electrical Limited | Construction | 2022 |
| Oundle Festival of Literature | Arts & recreation | 2007 |
| Oundle Fitness Ltd | Arts & recreation | 2011 |
| Oundle Living Spaces Ltd | Construction | 2018 |
| Oundle Luxury Car Hire Limited | Administrative & support | 2026 |
| Oundle Mencap Holidays Ltd | Health & social care | 2005 |
| Oundle MOT and Service Centre Limited | Wholesale & retail | 2020 |
| Oundle Osteopaths Limited | Health & social care | 2014 |
| Oundle Property Investment Company Limited | Construction | 1987 |
| Oundle Re-Finishing Services Ltd | Wholesale & retail | 2023 |
| Oundle Rifle and Pistol Club Limited | Arts & recreation | 2025 |
| Oundle School International Limited | Professional & scientific | 2024 |
| Oundle Smart Repairs Ltd | Wholesale & retail | 2019 |
| Oundle Software Services Ltd | Information & communication | 2017 |
| Oundle Tiling Ltd | Construction | 2018 |
| Oundle Town Football Club and Oundle Town Junior Football Club | Arts & recreation | 2016 |
| Oundle Town Rowing Club Limited | Arts & recreation | 2007 |
| OUR Thos, Property and Leisure Ltd | Real estate | 1988 |
| Ouse Valley Gymnastics Academy Ltd | Education | 2026 |
| OUT and About Services Ltd | Manufacturing | 2023 |
| Outdoor Power Equipment Limited | Information & communication | 2003 |
| Outdoor Visual Communications Limited | Manufacturing | 2017 |
| Outfitify Ltd | Information & communication | 2026 |
| Outside Space Solutions Ltd | Other services | 2022 |
| Outside the Books Limited | Education | 2022 |
| Outsorc Ltd | Professional & scientific | 2009 |
| Outtafocus Productions CIC | Professional & scientific | 2022 |
| Oveal FX Ltd | Financial services | 2025 |
| Ovela Ltd | Construction | 2018 |
| Overcome Aesthetics Limited | Public administration | 2023 |
| Overflow Oceans Ltd | Real estate | 2024 |
| Overseas Growth Partners Ltd | Professional & scientific | 2025 |
| Overwatch Intelligence Limited | Information & communication | 2024 |
| Ovidiu Express Logistics Ltd | Transport & logistics | 2024 |
| Owen Mooney Visuals Ltd | Professional & scientific | 2025 |
| Owlcat Media Ltd | Information & communication | 2024 |
| Own Trust | Education | 2018 |
| Owned by ALL CLG Ltd | Financial services | 2025 |
| Oxcroft Support Ltd | Health & social care | 2025 |
| Oxney Autos Ltd | Administrative & support | 2024 |
| Oxney Breakers Limited | Administrative & support | 2017 |
| Oxonar Ltd | Administrative & support | 2017 |
| Oxygen Beauty & Salon Ltd | Other services | 2026 |
| Oxygen Therapy Wellness Clinic Ltd | Health & social care | 2025 |
| Oxygenhair Ltd | Other services | 2020 |
| Oyoko Ltd | Professional & scientific | 2018 |
| Oyster Personnel Ltd | Construction | 2016 |
| OZ Valeting Ltd | Administrative & support | 2024 |
| OZK Architect Ltd | Professional & scientific | 2024 |
| Ozmanli Limited | Hospitality | 2025 |
| Ozuk Booze Ltd | Wholesale & retail | 2022 |
| Ozvanta Limited | Extraterritorial | 2013 |
| O’Mila Consulting Ltd | Professional & scientific | 2025 |
| P & F Sport Ltd | Education | 2018 |
| P & G 2014 Limited | Professional & scientific | 2014 |
| P & H Limited | Financial services | 2019 |
| P & L Farm Enterprises Ltd | Other services | 2023 |
| P & L Motors (Holdings) Limited | Financial services | 2011 |
| P & L Motors Limited | Wholesale & retail | 2004 |
| P & R Retail Store Ltd | Wholesale & retail | 2024 |
| P & S Electrical (Peterborough) Ltd | Construction | 2009 |
| P a Packaging Solutions Limited | Transport & logistics | 2004 |
| P B Business Developments Limited | Professional & scientific | 2010 |