| Oscar LEO T.M Ltd | Public administration | 2025 |
| Oscars Creative Limited | Other services | 2025 |
| Osdsuk Ltd | Wholesale & retail | 2022 |
| Osmaston Regeneration Partnership LLP | | 2015 |
| Ossett Furnishings (UK) Ltd | Manufacturing | 2010 |
| Ostac Health Care and Trading Consultation Services Limited | Administrative & support | 2025 |
| Ostara Aesthetics Ltd | Other services | 2022 |
| Osy’S Kitchen Limited | Hospitality | 2024 |
| OTC Global LP | | 2020 |
| Otcco Limited | Professional & scientific | 2020 |
| Otto Topco Ltd | Financial services | 2022 |
| Otto Wine Bar Ltd | Hospitality | 2024 |
| Oulton Plant Limited | Construction | 2016 |
| Ounkar Homes Ltd | Real estate | 2025 |
| OUR Brand Limited | Professional & scientific | 1962 |
| OUR Duas CIC | Health & social care | 2025 |
| OUR Lady of Doncaster Umbrella Trust | Education | 2014 |
| Ouroboros UK Capital Limited | Real estate | 2021 |
| OUT Running Limited | Professional & scientific | 2024 |
| OUT Youth C.I.C. | Education | 2016 |
| Outdoor Living Installations Limited | Extraterritorial | 2026 |
| Outdoor Sport Channel Ltd | Manufacturing | 2019 |
| Outlier 360 Limited | Information & communication | 2023 |
| OUTLIER360WAY Ltd | Professional & scientific | 2024 |
| Outpostember Ltd | Information & communication | 2025 |
| Outthereapp Ltd | Information & communication | 2018 |
| Oval Convenience Ltd | Wholesale & retail | 2020 |
| Oval Convenience Store Limited | Wholesale & retail | 2017 |
| Oval Globe Limited | Administrative & support | 2011 |
| Ovaltine Limited | Health & social care | 2019 |
| Ovatransport Ltd | Transport & logistics | 2023 |
| Ovenbloom Ltd | Extraterritorial | 2026 |
| Overhead Line Limited | Administrative & support | 2017 |
| Overline MF Ltd | Information & communication | 2026 |
| Overtee Property Ltd | Real estate | 2026 |
| OVO Healthcare Recruitment Specialist Ltd | Health & social care | 2025 |
| Owen Creative Limited | Arts & recreation | 2020 |
| Owen Energy Ltd | Manufacturing | 2017 |
| Owle Limited | Professional & scientific | 2014 |
| Own Logo Limited | Extraterritorial | 2013 |
| Own Logo Supply Company Limited | Extraterritorial | 2013 |
| Owston Court Residential Home Limited | Extraterritorial | 1993 |
| Owston Estate Company Limited(The) | Hospitality | 1976 |
| Owston Garden Properties Ltd | Professional & scientific | 2011 |
| Owston Park Golf Course Limited | Arts & recreation | 2003 |
| Owston Road Developments Ltd | Construction | 2025 |
| Owston Village Management Company Limited | Households | 1990 |
| OX E-Gen Ltd | Information & communication | 2025 |
| Oxen Sports Limited | Manufacturing | 2017 |
| Oxford Tutors & Clinical Services Limited | Education | 2016 |
| Oxley Industries Limited | Professional & scientific | 2022 |
| Oxygen Yachting Ltd | Extraterritorial | 2025 |
| Oxylog Ltd | Transport & logistics | 2026 |
| Oyster Pro-Training Limited | Arts & recreation | 2008 |
| OZ Cladding Ltd | Construction | 2020 |
| Ozbey Limited | Wholesale & retail | 2023 |
| Ozrr Ltd | Transport & logistics | 2025 |
| P & C Groundworks Limited | Construction | 2015 |
| P & G Specialist Contracts Limited | Construction | 2011 |
| P & K Property Developers Ltd | Construction | 2023 |
| P & L Middleton Ltd | Construction | 2017 |
| P & L Upholstery Limited | Wholesale & retail | 2002 |
| P & R Spraying Ltd | Wholesale & retail | 2021 |
| P a Payrolls Ltd | Administrative & support | 2015 |
| P B Construction ( Yorkshire ) Ltd | Construction | 2019 |
| P B Property Portfolio Ltd | Real estate | 2020 |
| P B Trading Limited | Wholesale & retail | 2014 |
| P Clad Limited | Construction | 2022 |
| P Dillyspoon Limited | Hospitality | 2019 |
| P E Dillyspoons Limited | Hospitality | 2015 |
| P G Kennels Limited | Agriculture & fishing | 2024 |
| P G MAC Limited | Manufacturing | 2008 |
| P H Clark (High Burnham) Limited | Agriculture & fishing | 2017 |
| P H M & C E Consultancy Limited | Construction | 2014 |
| P J Joinery (Nottingham) Limited | Construction | 2003 |
| P P Joinery Services Ltd | Construction | 2026 |
| P Price Properties Ltd | Real estate | 2023 |
| P Tate Ltd | Construction | 2007 |
| P V Castle Limited | Real estate | 2003 |
| P W: Winslow Utilities Limited | Construction | 2011 |
| P Walton Joinery Limited | Construction | 2024 |
| P Watson Joinery Ltd | Construction | 2020 |
| P&C Window Cleaning Limited | Administrative & support | 2015 |
| P&D Properties Doncaster Limited | Real estate | 2024 |
| P&F Solutions Ltd | Wholesale & retail | 2022 |
| P&J Services Ltd | Transport & logistics | 2023 |
| P&K Aircraft Maintenance Consulting Ltd | Professional & scientific | 2011 |
| P. C. Excavations Limited | Construction | 2008 |
| P. Foster Financial Planning Ltd | Financial services | 2013 |
| P.B. Properties (Hatfield) Ltd | Professional & scientific | 1998 |
| P.B. Robinson (Doncaster) Limited | Health & social care | 2011 |
| P.B.Metals Ltd | Wholesale & retail | 2023 |
| P.F.C. Dienstverlening Limited | Transport & logistics | 2011 |
| P.Hughes Builders Ltd | Construction | 2001 |
| P.J Nightingale Ltd | Transport & logistics | 2002 |
| P.M Trailers and Horse Box Ltd | Transport & logistics | 2022 |
| P.M.C. Surveys Limited | Mining & quarrying | 2009 |
| P.M.W Services Ltd | Wholesale & retail | 2019 |
| P.S. Construction (Doncaster) Limited | Construction | 1970 |
| P.S.G. Investments Limited | Wholesale & retail | 1996 |