| One GAV Ltd | Construction | 2023 |
| One Health Home Care Limited | Administrative & support | 2022 |
| One JOB Inc Limited | Construction | 2019 |
| One Love Caribbean Restaurant Limited | Hospitality | 2013 |
| One Man’S Hands Ltd | Construction | 2018 |
| One Ocean International Limited | Administrative & support | 2023 |
| One Percent Extra Ltd | Wholesale & retail | 2022 |
| One Pound Holidays Ltd | Wholesale & retail | 2026 |
| One Ranger Film Ltd | Information & communication | 2022 |
| One Ring Accountancy Services Limited | Professional & scientific | 2005 |
| One Star Tyres Ltd | Wholesale & retail | 2016 |
| One Stop Fencing * Ltd | Financial services | 2025 |
| One Stop General Store Ltd | Wholesale & retail | 2025 |
| One Stop Logistic Solutions Ltd | Transport & logistics | 2024 |
| One Stop Office & Educational Supplies Ltd | Wholesale & retail | 2021 |
| One Stop Plumbing & Electrical Services Ltd | Wholesale & retail | 2021 |
| One Two Seven One Limited | Real estate | 2018 |
| ONE2TRUST Ltd | Other services | 2017 |
| ONE3SEVEN Socials Limited | Professional & scientific | 2025 |
| Onederfull Ltd | Professional & scientific | 2025 |
| Oneman Transit Limited | Transport & logistics | 2025 |
| ONEMED23 Ltd | Health & social care | 2023 |
| Onesource Partnership Ltd | Administrative & support | 2014 |
| Onestopkids Limited | Wholesale & retail | 2020 |
| Onestore Retail Ltd | Wholesale & retail | 2022 |
| Onet Media Ltd | Information & communication | 2012 |
| Onetouch DP Limited | Manufacturing | 2017 |
| Onetrak Consulting Limited | Construction | 2018 |
| Onetrust Property Solutions Ltd | Hospitality | 2025 |
| ONEXP315 Ltd | Information & communication | 2025 |
| Ongar Taxi Ltd | Transport & logistics | 2024 |
| Online Conveyancing 4U Limited | Professional & scientific | 2018 |
| Online Deals Limited | Wholesale & retail | 2026 |
| Online Research Team Ltd | Professional & scientific | 2017 |
| Online Schooling Ltd | Education | 2022 |
| Online Seller Ltd | Wholesale & retail | 2023 |
| Only Fools Hospitality Limited | Hospitality | 2019 |
| Onpoint Youth Enterprise Support Services Ltd | Administrative & support | 2018 |
| ONS FX Ltd | Financial services | 2022 |
| Onsea Travel Ltd | Administrative & support | 2020 |
| Onstaffing Recruitment Ltd | Administrative & support | 2023 |
| Onsurv Limited | Professional & scientific | 2020 |
| Ontime Facade Ltd | Construction | 2022 |
| Ontrack Athletics Limited | Manufacturing | 2023 |
| Onward Support Ltd | Hospitality | 2019 |
| Onwood for Chairs Ltd | Wholesale & retail | 2020 |
| Onyx Facilities Ltd | Wholesale & retail | 2021 |
| Onyx FM Ltd | Administrative & support | 2018 |
| Onyx Guarding Ltd | Administrative & support | 2022 |
| Onyx House RTM Company Limited | Households | 2025 |
| Onyx Stone Ltd | Construction | 2012 |
| OOH HOO Ltd | Wholesale & retail | 2026 |
| OP Vapez Ltd | Wholesale & retail | 2023 |
| Opal & Grace Construction Ltd | Construction | 2020 |
| OPE Cove Ltd | Manufacturing | 2024 |
| Open Arms Property Ltd | Real estate | 2022 |
| Open Clothing UK Ltd | Wholesale & retail | 2025 |
| Open Junction Networks Limited | Public administration | 2012 |
| Open Sound Music & Research (Osmr) CIC | Information & communication | 2025 |
| Open Window Technical Ltd | Construction | 2022 |
| Open World 2 Limited | Real estate | 2016 |
| Open World One Limited | Real estate | 2024 |
| Openview Electrical Solutions Limited | Extraterritorial | 2014 |
| Openview Group Limited | Professional & scientific | 2004 |
| Openview Security Systems Limited | Extraterritorial | 2021 |
| Openworld Security Services Limited | Administrative & support | 2023 |
| Opera Restaurant & Events Limited | Hospitality | 2017 |
| Opera Restaurant Limited | Hospitality | 2015 |
| OPI Constructions Ltd | Construction | 2019 |
| OPM Global Solar Limited | Construction | 2025 |
| Oppo Cars Ltd | Wholesale & retail | 2018 |
| Opposite Clothing Company (OCC) Limited | Wholesale & retail | 2024 |
| OPS Solutions Limited | Administrative & support | 2010 |
| Opsinsight Ltd | Professional & scientific | 2024 |
| Optical Homecare Limited | Health & social care | 2019 |
| Optihomes Management Ltd | Real estate | 2024 |
| Optima Herbs Ltd | Wholesale & retail | 2025 |
| Optima Tech Solutions Ltd | Wholesale & retail | 2021 |
| Optimal Caretech Ltd | Health & social care | 2023 |
| Optimal Cleaning Solutions England Limited | Administrative & support | 2014 |
| Optimal RPO Limited | Administrative & support | 2019 |
| Optimalcleaningdivision Ltd | Administrative & support | 2025 |
| Optimum Healthcare Support Limited | Health & social care | 2022 |
| Optimus AI Limited | Information & communication | 2020 |
| Optimus Autos Services Limited | Wholesale & retail | 2024 |
| Optimus Build Solutions Ltd | Construction | 2025 |
| Optimus Deluxe Ltd | Other services | 2015 |
| Optimus Planning Ltd | Professional & scientific | 2021 |
| Optimus Steel Ltd | Construction | 2021 |
| Optishire Ltd | Wholesale & retail | 2025 |
| Optiusnow Limited | Information & communication | 2025 |
| Optom Recruit Ltd | Health & social care | 2024 |
| Opulent Executive Drives Ltd | Transport & logistics | 2025 |
| Opuloria Ltd | Wholesale & retail | 2025 |
| Opulus Services Ltd | Other services | 2022 |
| Opus Conservation Ltd | Arts & recreation | 2018 |
| OPW Gate House Limited | Real estate | 2025 |
| OPW P2 Limited | Construction | 2021 |
| Orama Consultancy Ltd | Information & communication | 2022 |
| Orama Holdings Ltd | Real estate | 2021 |