| Opulex Limited | Professional & scientific | 2025 |
| Orange 154 Consultancy Limited | Information & communication | 2019 |
| Orange Tree Joinery Limited | Construction | 2018 |
| Oranva Limited | Real estate | 2026 |
| Orbbits Ltd | Other services | 2022 |
| Orbis Logistics Limited | Transport & logistics | 2026 |
| Orbitapp Ltd | Information & communication | 2025 |
| Orbitdelta Ltd | Wholesale & retail | 2016 |
| Orbiter Club Ltd | Professional & scientific | 2014 |
| Orbitercard Ltd | Other services | 2013 |
| Orchard Mews (Knaphill) Management Company Limited | Households | 2003 |
| Orchid Foods Ltd | Hospitality | 2025 |
| ORD Limited | Construction | 2025 |
| Organic Juice Bar Ltd | Manufacturing | 2026 |
| Orienta Limited | Wholesale & retail | 2018 |
| Oriental RUG Import Centre Ltd | Wholesale & retail | 2018 |
| Origin Glass Limited | Construction | 2019 |
| Original Souvlaki Ltd | Hospitality | 2020 |
| Orion Care Group Limited | Health & social care | 2023 |
| Orion Investment Holdings Limited | Real estate | 2022 |
| Oris (London) Limited | Extraterritorial | 2015 |
| Orista Trading Limited | Wholesale & retail | 2025 |
| Orkin Limited | Wholesale & retail | 1964 |
| Orla Developments Limited | Construction | 2014 |
| Ornate Rugs Limited | Wholesale & retail | 2015 |
| Ortho-Tek Limited | Health & social care | 2006 |
| Orthotic Consultants Ltd | Health & social care | 2010 |
| OS Events Ltd | Administrative & support | 2019 |
| OS Incorporation Ltd | Wholesale & retail | 2024 |
| OSA Lettings Ltd | Real estate | 2025 |
| OSA11 Limited | Health & social care | 2019 |
| OSA11 Properties Limited | Real estate | 2020 |
| Oscar Glass & Glazing Services Limited | Construction | 2021 |
| Oscar Krane (OK) Ltd | Administrative & support | 2022 |
| Oscars Property Limited | Real estate | 2020 |
| Osidge Services Limited | Construction | 2020 |
| OSM Design & Build Ltd | Construction | 2026 |
| OSM Import & Export Trading Limited | Wholesale & retail | 2020 |
| Osman Pharma Services Limited | Wholesale & retail | 2006 |
| Osmondthorpe Convenience Store Ltd | Wholesale & retail | 2024 |
| Ospac Ltd | Transport & logistics | 2023 |
| Ostrider Limited | Transport & logistics | 2012 |
| Ostro Shipping Limited | Transport & logistics | 2024 |
| OT Nepalese Cuisine Ltd | Hospitality | 2015 |
| OT Property Group Ltd | Real estate | 2025 |
| Otowax Removal Limited | Wholesale & retail | 2022 |
| OU Holdings Ltd | Financial services | 2024 |
| OUD AL Muadh Limited | Wholesale & retail | 2018 |
| OUR Vishva Ltd | Real estate | 2022 |
| OUS & Services Ltd | Administrative & support | 2024 |
| Outfit Security Limited | Administrative & support | 2017 |
| Outlined. Ltd | Wholesale & retail | 2025 |
| Outoftheportal Ltd | Wholesale & retail | 2025 |
| Outsiders Productions Ltd. | Information & communication | 2025 |
| Outwittech Limited | Information & communication | 2022 |
| Overbrook Forecourt Ltd | Real estate | 2024 |
| Overhaul Technology Limited | Information & communication | 2023 |
| Overseas Success Ltd | Professional & scientific | 2023 |
| Ovrt Limited | Education | 2021 |
| OWK Garden Chemicals Ltd | Other services | 2023 |
| Owner Scale Ltd | Financial services | 2026 |
| Oxford & Hawthorne Technologies Limited | Information & communication | 2025 |
| Oxford Biotech Limited | Professional & scientific | 2024 |
| Oxford Cardiomox Ltd | Professional & scientific | 2013 |
| Oxytal Limited | Information & communication | 2025 |
| OYA Group Ltd | Wholesale & retail | 2023 |
| OYR Automotive Ltd | Wholesale & retail | 2025 |
| OZ Solutions Ltd | Real estate | 2024 |
| Ozone Abrasives Limited | Wholesale & retail | 2015 |
| Ozone Laundry Limited | Other services | 2018 |
| Ozone Medical Supplies Ltd | Wholesale & retail | 2014 |
| Ozzyhair Ltd | Other services | 2026 |
| P & K Property Limited | Real estate | 2018 |
| P & P Accountancy Services Limited | Professional & scientific | 2012 |
| P & P Distributors Ltd | Transport & logistics | 2021 |
| P & P UK Investments Limited | Real estate | 2024 |
| P and P Brothers Ltd | Transport & logistics | 2025 |
| P Energy Limited | Transport & logistics | 2013 |
| P J Kidderminster Limited | Hospitality | 2016 |
| P K & Groups Ltd | Wholesale & retail | 2026 |
| P O Relief Limited | Wholesale & retail | 2008 |
| P S Palmer & Associates Limited | | 1961 |
| P Y Logistics Ltd | Professional & scientific | 2020 |
| P&B Corporation Limited | Wholesale & retail | 2024 |
| P&D Kiraly Construction Ltd | Construction | 2022 |
| P&L Philmart Ltd | Wholesale & retail | 2021 |
| P&M Car Sales Ltd | Wholesale & retail | 2023 |
| P&M Food & Wine 24/7 Limited | Wholesale & retail | 2024 |
| P&P Packaging Ltd | Wholesale & retail | 2024 |
| P&R Distribution Limited | Transport & logistics | 2011 |
| P&S Consulting UK Ltd | Professional & scientific | 2014 |
| P&S Trans Ltd | Transport & logistics | 2025 |
| P.Rincemount (Holdings) Ltd | Financial services | 2018 |
| P3 Partners Limited | Real estate | 2016 |
| P3M Project Services Limited | Other services | 2019 |
| Paai Ltd | Real estate | 2026 |
| Paarth Event Management Limited | Hospitality | 2023 |
| Paavan Developments Limited | Real estate | 2023 |
| PAB Wiring Ltd | Information & communication | 2014 |
| Pacif Ocean Limited | Administrative & support | 2021 |