| One Click Order Ltd | Wholesale & retail | 2019 |
| One Go Consultancy Limited | Wholesale & retail | 2025 |
| One Konekt Limited | Construction | 2020 |
| One Point Seven Ltd | Real estate | 2026 |
| One Pound Stores Ltd | Wholesale & retail | 2025 |
| One Stop Success Limited | Arts & recreation | 2013 |
| One Tree Fitting Limited | Construction | 2026 |
| One World Acquisitions Ltd | Transport & logistics | 2017 |
| One World Commercial Real Estate Ltd | Real estate | 2017 |
| One World Developments Limited | Real estate | 2015 |
| One World E-Commerce Limited | Other services | 2017 |
| One World Group Services Limited | Transport & logistics | 2015 |
| One World Holdings Limited | Financial services | 2015 |
| One World Real Estate (UK) Limited | Real estate | 2014 |
| One World Solutions (UK) Ltd | Information & communication | 2014 |
| One-Four 'C' Limited | Professional & scientific | 2022 |
| Ones Thai Therapy Limited | Other services | 2025 |
| Oneten 110 Limited | Wholesale & retail | 2025 |
| Onkaar & Co Ltd | Information & communication | 2018 |
| Onkaar Brother Properties Ltd | Real estate | 2023 |
| Onkaar Brothers Group Ltd | Real estate | 2021 |
| Onkaar Home Essentials Ltd | Wholesale & retail | 2019 |
| Onkaar Home Store Ltd | Wholesale & retail | 2019 |
| Onkar Property Limited | Real estate | 2025 |
| Onkar Transport Ltd | Transport & logistics | 2023 |
| Onlo General Intelligence Ltd | Manufacturing | 2024 |
| Ontime Concrete Ltd | Manufacturing | 2022 |
| Onyx Group International Ltd | Manufacturing | 2023 |
| Open Club Ltd | Professional & scientific | 2026 |
| Opiant Technologies Limited | Information & communication | 2026 |
| Opinder Services Ltd | Administrative & support | 2016 |
| Optimus Services Limited | Information & communication | 2024 |
| Optimus Stores Ltd | Wholesale & retail | 2022 |
| Option Roomzzz Ltd | Real estate | 2020 |
| Opulence Business Limited | Wholesale & retail | 2024 |
| Opulent Assets Ltd | Real estate | 2024 |
| Oracle Investment Property Ltd | Real estate | 2025 |
| Oracle Plumbing and Heating Ltd | Construction | 2022 |
| Oracle Real Estate Ltd | Real estate | 2023 |
| Oradea Ltd | Wholesale & retail | 2024 |
| Orant Ltd | Wholesale & retail | 2022 |
| Orbis Unum Limited | Information & communication | 2015 |
| Orbit Bazaar Ltd | Wholesale & retail | 2025 |
| Orbit Infolabs Ltd | Information & communication | 2025 |
| Orca Property Ltd | Real estate | 2024 |
| Orchard (Hillingdon) Limited | Professional & scientific | 2002 |
| Orchard Cottages (Woking) Management Company Limited | Real estate | 2003 |
| Orchard Hub Limited | Construction | 2017 |
| Orchids Services Ltd | Information & communication | 2025 |
| Order Pros Ltd | Wholesale & retail | 2022 |
| Organisation for Humanitarian Initiatives (OHI) | Professional & scientific | 2024 |
| Orhum Ltd | Wholesale & retail | 2025 |
| Orientation Philosophy Limited | Information & communication | 2020 |
| Origin Metals Ltd | Wholesale & retail | 2026 |
| Origin Private Ltd | Manufacturing | 2026 |
| Original Skankers Entertainment Ltd | Manufacturing | 2020 |
| Original Staffing Services Ltd | Administrative & support | 2021 |
| Orlando Fish & Chips Limited | Wholesale & retail | 2008 |
| Orlando VR Ltd | Hospitality | 2023 |
| Ornate Global Ltd | Wholesale & retail | 2024 |
| Ortho-Tools Ltd | Professional & scientific | 2021 |
| Orvanta Global Ltd | Wholesale & retail | 2026 |
| Oryzaf Ltd | Wholesale & retail | 2025 |
| Oscar Construction London Limited | Construction | 2025 |
| Oscars Auto Ltd | Wholesale & retail | 2022 |
| Oscars Car Limited | Transport & logistics | 2025 |
| OSM Wholesale Ltd | Wholesale & retail | 2021 |
| Osman Transport Service Ltd | Other services | 2020 |
| OSN Development Limited | Construction | 2018 |
| Ostfrost UK Ltd | Professional & scientific | 2013 |
| Ostia Lodge (Hayes) RTM Company Limited | Households | 2025 |
| OTP Ltd | Transport & logistics | 2022 |
| Otter 59 Ltd | Real estate | 2013 |
| OUM SG Ltd | Hospitality | 2024 |
| OUS Holdings Limited | Financial services | 2025 |
| Outsource Plus Ltd | Professional & scientific | 2019 |
| Outwell Local Ltd | Wholesale & retail | 2024 |
| Ovia Designers Ltd | Wholesale & retail | 2016 |
| OVR Property Management Ltd | Real estate | 2026 |
| OVR Residencies Ltd | Hospitality | 2026 |
| Ovrgroupholdings Ltd | Financial services | 2026 |
| Owais Trading Ltd. | Wholesale & retail | 2025 |
| OWK Books Ltd | Information & communication | 2025 |
| Own Make Ltd | Wholesale & retail | 2018 |
| OX26 Developments Ltd | Real estate | 2026 |
| Oxford Developer Ltd | Construction | 2024 |
| Oxigenbuilders Limited | Construction | 2025 |
| Oxygen BI Limited | Information & communication | 2022 |
| Oyomon Ltd | Information & communication | 2023 |
| Oyster-Cnc Precision Engineering Ltd | Professional & scientific | 2023 |
| Oza&Sons Construction Ltd | Construction | 2025 |
| P & G Builders Ltd | Construction | 2014 |
| P & K Bedroom & Kitchen Ltd | Construction | 2019 |
| P &P Construction Ltd | Construction | 2025 |
| P and P Property Private Limited | Real estate | 2020 |
| P and W Easyshop Ltd | Wholesale & retail | 2024 |
| P B First Ltd | Real estate | 2021 |
| P Chopra Estates Ltd | Real estate | 2025 |
| P Kumar Limited | Construction | 2017 |
| P P Lounge & Bar Ltd | Hospitality | 2019 |