| OHL Holdings Ltd | Professional & scientific | 2015 |
| OK Subsurface Geosolutions Ltd | Professional & scientific | 2025 |
| Olcay Chef Ltd | Hospitality | 2020 |
| Olcay Desserts Ltd | Hospitality | 2020 |
| Old Place (Lindfield) Limited | Households | 1993 |
| Old Shoreham Road 2 Limited | Real estate | 2021 |
| Old Shoreham Road Leases Limited | Real estate | 2023 |
| Old Shoreham Road Ltd | Construction | 2019 |
| Oldbury Motors Limited | Wholesale & retail | 2003 |
| Oldbus Limited | Arts & recreation | 1980 |
| Olive Tree Enterprises Limited | Real estate | 2010 |
| Oliver Trade Solutions Ltd | Construction | 2022 |
| Olympass Security Solutions Limited | Administrative & support | 2005 |
| Oncet Ltd | Wholesale & retail | 2025 |
| One Broad Street Management Limited | Real estate | 2018 |
| One Fashion Loft Ltd | Wholesale & retail | 2025 |
| One Legal Square Ltd | Professional & scientific | 2015 |
| One Smart Place Limited | Extraterritorial | 2011 |
| One Station Street Limited | Administrative & support | 1959 |
| Onefourfour Investments Ltd | Real estate | 2018 |
| Onefourfour Limited | Real estate | 2017 |
| Onionalgo Limited | Real estate | 2015 |
| Only-Engage Limited | Professional & scientific | 2011 |
| Onso Studios Ltd | Construction | 2025 |
| Onyx Partnership Ltd | Real estate | 2018 |
| Oopla Ltd | Information & communication | 2025 |
| Oozoo UK Limited | Extraterritorial | 1994 |
| Opaal Limited | Real estate | 2019 |
| Open Advice Limited | Professional & scientific | 2021 |
| Open Verse Music Ltd | Education | 2025 |
| Openview Exteriors Ltd | Construction | 2024 |
| Optifast Technologies Ltd | Administrative & support | 2025 |
| Optima 360 Solutions Ltd | Professional & scientific | 2025 |
| Optimum Commercial Limited | Professional & scientific | 2017 |
| Optimum Global Limited | Financial services | 2005 |
| Opus 28 Limited | Administrative & support | 2010 |
| Orange Roost Limited | Administrative & support | 2010 |
| Orangetree Developments Limited | Real estate | 2004 |
| Orbital Site Services Limited | Construction | 2007 |
| Orbital Site Solutions Limited | Construction | 2024 |
| Orchard Gate (Bolney) Management Limited | Households | 1997 |
| Orchard Way (Warninglid) Limited | Households | 1997 |
| Orien Beauty & Selfcare Limited | Wholesale & retail | 2018 |
| Orion (Oxshott) Ltd | Construction | 2014 |
| Orla Limited | Hospitality | 2024 |
| Orpington GPO Ltd | Hospitality | 2019 |
| Orynoco Ltd | Other services | 2020 |
| Osborne Mews (Management) Limited | Professional & scientific | 2003 |
| Osiers Aviation Limited | Professional & scientific | 2019 |
| OSS SMA Ltd | Real estate | 2025 |
| Otacon Engineering Limited | Information & communication | 2021 |
| Ottafield Court Limited | Households | 2011 |
| Otterden Management Limited | Real estate | 2003 |
| OUH LA LA Limited | Wholesale & retail | 2006 |
| Ounce Stores Limited | Wholesale & retail | 2020 |
| OUR Home Rentals Ltd | Construction | 2024 |
| Ouse Angling Preservation Society Limited | Arts & recreation | 2005 |
| Outbound Automotive Limited | Administrative & support | 2021 |
| Outbound Calls Limited | Administrative & support | 2020 |
| Outdoor Adventure Hire Ltd | Administrative & support | 2025 |
| Outeniqua Properties Limited | Real estate | 2022 |
| Outlap Limited | Financial services | 2020 |
| Outstation Ltd | Professional & scientific | 2022 |
| OVP Tools Ltd | Wholesale & retail | 2024 |
| Owen Garages Limited | Administrative & support | 2006 |
| OXB Limited | Information & communication | 2021 |
| Ozone Design Limited | Professional & scientific | 2004 |
| O’Hara Financial Planning Limited | Professional & scientific | 2018 |
| P & S Gallagher Limited | Other services | 1991 |
| P D F Roofing Limited | Construction | 2015 |
| P J Properties & Maintenance Limited | Construction | 2023 |
| P Janes Limited | Construction | 2006 |
| P W Jobbins Ltd | Construction | 2026 |
| P&C Sussex Properties Ltd | Real estate | 2022 |
| P&P Comms Limited | Information & communication | 2010 |
| P. G. Bish Limited | Construction | 1976 |
| P.B. Mortgages & Protection Ltd | Financial services | 2026 |
| P.O.E.T. Investments Limited | Financial services | 2025 |
| P.R. Lighting Systems Limited | Manufacturing | 1994 |
| Pabrico Panels Limited | Manufacturing | 1970 |
| PAC Handyman Services Limited | Construction | 2011 |
| Packets Global Limited | Information & communication | 2016 |
| Paddock (Maresfield) Management Company Limited(The) | Households | 1986 |
| Page Security Limited | Administrative & support | 2006 |
| Paintgate Limited | Professional & scientific | 2001 |
| Pakar Services Limited | Financial services | 2020 |
| Palus Investments Ltd | Construction | 2004 |
| PAN PDA Company Limited | Financial services | 2024 |
| PAN Professional Trusteeship Limited | Financial services | 2020 |
| PAN Sole Trustees Limited | Financial services | 2020 |
| PAN Trustees UK LLP | | 2007 |
| Pancake Productions Ltd | Information & communication | 2023 |
| Panel Print Limited | Manufacturing | 2007 |
| Panmoto Ltd | Wholesale & retail | 2024 |
| PAP (SE18) Limited | Real estate | 2021 |
| Papiko Limited | Information & communication | 2016 |
| Paradigm Leisure Limited | Real estate | 2017 |
| Parcomm Cabling Limited | Extraterritorial | 2010 |
| Parcomm Limited | Information & communication | 2000 |
| Pargeter Property Investments Ltd | Real estate | 2024 |