| Only One Design Limited | Other services | 2019 |
| Only the Best Agency Ltd | Professional & scientific | 2015 |
| Onpoint Prosthetics Ltd | Health & social care | 2026 |
| Onyx Holdings Corporation Ltd | Financial services | 2025 |
| Opaline Offices Ltd | Administrative & support | 2024 |
| OPD Hitchin Limited | Health & social care | 2023 |
| Open and Shut Holdings Limited | Financial services | 2021 |
| Open View Property Services Ltd | Real estate | 2021 |
| Ophelia Myers Ltd | Information & communication | 2024 |
| Opko Ltd | Professional & scientific | 2022 |
| OPS Search & Selection Limited | Administrative & support | 2008 |
| Opsica Security Ltd | Administrative & support | 2019 |
| Optical Technologies-Uk Limited | Manufacturing | 2019 |
| Optilium Limited | Professional & scientific | 2016 |
| Optima Accountancy Services Limited | Professional & scientific | 2010 |
| Optima-Hoofware Ltd | Manufacturing | 2015 |
| Optime Lighting Limited | Manufacturing | 1994 |
| Optimum Build Ltd | Manufacturing | 2025 |
| Optiom Health Limited | Wholesale & retail | 2023 |
| Options Waste Water Solutions Limited | Professional & scientific | 2015 |
| Orange Lady Limited | Administrative & support | 2023 |
| Orange Lion Property Ltd | Real estate | 2023 |
| Orbiit Ltd | Information & communication | 2026 |
| Orchard Commercial Lettings Ltd | Administrative & support | 2010 |
| Orchard Home Developments Limited | Construction | 2017 |
| Orchard Property Services Ltd | Construction | 2009 |
| Original Juice Design Limited | Professional & scientific | 2005 |
| Original Yoga Limited | Arts & recreation | 2023 |
| Orion Aviation Limited | Transport & logistics | 2015 |
| Orlene's Kitchen Catering & Events Management Ltd | Hospitality | 2022 |
| Ortho Paed Medical Ltd | Professional & scientific | 2011 |
| Oryx JET Aircraft Management Limited | Transport & logistics | 2009 |
| Oryx JET Limited | Transport & logistics | 2009 |
| OS Pizza Bar Ltd | Hospitality | 2025 |
| Osaka Limited | Real estate | 2002 |
| Osaka Property Investment Limited | Professional & scientific | 2022 |
| Oscaro Comms Limited | Information & communication | 2026 |
| Osgood Editorial Ltd | Professional & scientific | 2022 |
| Osier Court Freeholders Company Limited | Households | 2021 |
| Osier Court Residents Management Company Limited | Households | 2003 |
| Osinsky's Limited | Extraterritorial | 2011 |
| Osprey Interiors Limited | Construction | 2021 |
| Osteopathics (HHR) Ltd | Health & social care | 2011 |
| Osteopathy First Limited | Health & social care | 2003 |
| OTE 2024 Limited | Arts & recreation | 2024 |
| OTE Concerts Ltd | Wholesale & retail | 2022 |
| Otway Developments Ltd | Construction | 2025 |
| Otway Group Ltd | Financial services | 2025 |
| Otway Investments Ltd | Real estate | 2025 |
| Oughtonhead Ltd | Professional & scientific | 2018 |
| OUR House Health Club Limited | Health & social care | 2025 |
| Outgrown Sports Ltd | Wholesale & retail | 2026 |
| Outlandish Campers Ltd | Manufacturing | 2020 |
| Overtheflipside Ltd | Professional & scientific | 2021 |
| Ovid Marketing and Design Limited | Professional & scientific | 2008 |
| OVO Productions Limited | Arts & recreation | 2023 |
| Owenfituk Ltd | Education | 2019 |
| OWL Bathrooms Limited | Wholesale & retail | 2023 |
| OWL Construction Services Ltd | Construction | 2023 |
| Oyster a B Limited | Real estate | 2022 |
| Ozona Limited | Manufacturing | 2006 |
| Ozric IT Solutions Limited | Information & communication | 2016 |
| O’Marah Ltd | Wholesale & retail | 2023 |
| P & D Allen (Farms) Limited | Agriculture & fishing | 2002 |
| P & F Bellwood Limited | Real estate | 2017 |
| P & L Network Limited | Information & communication | 1998 |
| P & P Laboratories Limited | Health & social care | 2009 |
| P a Underwood Flooring Limited | Construction | 2012 |
| P Diddy Black Excellence Limited | Wholesale & retail | 2025 |
| P E Marsden Limited | Professional & scientific | 2013 |
| P F Stevens Consultancy Limited | Financial services | 2013 |
| P J B Carpentry Limited | Construction | 2008 |
| P J Van Heerden NO 2 Limited | Health & social care | 2019 |
| P More PHC Limited | Construction | 2013 |
| P Secure Ltd | Administrative & support | 2021 |
| P. Jenson and Company Limited | Manufacturing | 1988 |
| P.J.E. Investments Ltd | Real estate | 2018 |
| Pace Asset Holdings Limited | Financial services | 2023 |
| Pace Interiors Limited | Manufacturing | 2006 |
| PAD Building Services Ltd | Construction | 2023 |
| Padbury Thomson Property Ltd | Households | 2024 |
| Padel Match Ltd | Arts & recreation | 2025 |
| Padl LDN Ltd | Wholesale & retail | 2025 |
| Padrino's House Ltd | Hospitality | 2026 |
| Paeds Medical Ltd | Health & social care | 2012 |
| Paeds Medicolegal Ltd | Health & social care | 2023 |
| Page Matthews Group Ltd | Administrative & support | 2021 |
| Paintercom Limited | Professional & scientific | 2014 |
| PAK Delivery Service Ltd | Transport & logistics | 2015 |
| Palehouse Building Company Limited | Construction | 2017 |
| Palehouse Building Services Limited | Construction | 2025 |
| Palehouse Commercial Interiors Ltd | Construction | 2021 |
| Palehouse Group Limited | Construction | 2024 |
| Pali Foods Limited | Manufacturing | 2024 |
| Pali Property Ltd | Hospitality | 2024 |
| Panorama Video Distribution Ltd | Information & communication | 2024 |
| Paper Crown Events Ltd | Administrative & support | 2024 |
| Paprika Nights Ltd | Hospitality | 2024 |
| Paradigm Property Trading Limited | Real estate | 1999 |
| Paragon Smart Systems Limited | Construction | 2026 |