| Octinvest Limited | Real estate | 2023 |
| Octio Communications Ltd | Education | 2020 |
| Octiveight Holdings Limited | Financial services | 2026 |
| Octo Architecture Ltd | Professional & scientific | 2017 |
| Octo Brickwork Ltd | Construction | 2024 |
| October Thirteen Ltd | Wholesale & retail | 2025 |
| Octolyte Limited | Wholesale & retail | 2025 |
| Octopus DCS Limited | Construction | 2017 |
| Octovate Ltd | Information & communication | 2022 |
| Oculus Group Holdings Limited | Households | 2024 |
| Oculus Housing Group Limited | Households | 2024 |
| Oculus Scaffolding Limited | Construction | 2026 |
| Ocuwell Limited | Professional & scientific | 2020 |
| OCW Security Limited | Administrative & support | 2025 |
| Odaallerton Ltd | Hospitality | 2025 |
| ODC Packaging Limited | Manufacturing | 2011 |
| Oddineers Limited | Wholesale & retail | 2012 |
| Oddiss Ltd | Information & communication | 2025 |
| Oddsock Developments Ltd | Real estate | 2024 |
| Oddwave Ltd | Wholesale & retail | 2024 |
| Odes Trade Ltd | Wholesale & retail | 2025 |
| Odessa OFF Licence Ltd | Wholesale & retail | 2025 |
| Odie Design Studio Ltd | Professional & scientific | 2022 |
| Odigos Supply Limited | Transport & logistics | 2021 |
| Odin Elite Protection Ltd | Administrative & support | 2025 |
| Odin Management Company Ltd | Extraterritorial | 2012 |
| Odin North West Limited | Health & social care | 2024 |
| Odiva Ltd | Households | 2026 |
| Odorem Scent Limited | Wholesale & retail | 2026 |
| Odox Ltd | Transport & logistics | 2011 |
| ODR Training Ltd | Information & communication | 2018 |
| Oduk Consultancy Ltd | Financial services | 2020 |
| Oduk Services Ltd | Wholesale & retail | 2024 |
| ODY Company Ltd | Professional & scientific | 2005 |
| ODY Legal Logistics Limited | Professional & scientific | 2014 |
| Odyssea Holdings & Investments Ltd | Real estate | 2019 |
| Odyssey Accounts Ltd | Administrative & support | 2025 |
| Odyssey Construction Services Limited | Construction | 2018 |
| Odyssey Network Limited | Professional & scientific | 1998 |
| OE Property Management Ltd | Real estate | 2024 |
| OEA Holdings Limited | Financial services | 2026 |
| OEC Reporting Limited | Health & social care | 2025 |
| OEP Energy Centres 2 Limited | Energy | 2021 |
| OEP Energy Centres Limited | Energy | 2021 |
| OF Kitchen Food Ltd | Hospitality | 2026 |
| OFF Grid Getaways UK Limited | Administrative & support | 2025 |
| OFF Licence Shop & Grocery Ltd | Wholesale & retail | 2025 |
| OFF Limits Group Limited | Arts & recreation | 2015 |
| OFF the Leash Dog Parks Ltd | Other services | 2025 |
| OFF the Pass Limited | Hospitality | 2018 |
| OFF the Runway Ltd. | Wholesale & retail | 2017 |
| OFF the Square Foods Ltd | Hospitality | 2008 |
| OFF Your Cake Ltd | Manufacturing | 2010 |
| Offerlaunch Ltd | Wholesale & retail | 1999 |
| Office 2 Home Ltd | Wholesale & retail | 2007 |
| Office Diamonds Ltd | Professional & scientific | 2026 |
| Office Furniture 2 YOU Ltd | Wholesale & retail | 2021 |
| Office Furniture Recycling Centres CIC | Wholesale & retail | 2013 |
| Official Shankly Merchandise Limited | Wholesale & retail | 2019 |
| Offley Bros Limited | Transport & logistics | 1945 |
| Offroad Crafts Ltd | Wholesale & retail | 2023 |
| Offseason Developments Ltd | Wholesale & retail | 2025 |
| Offset Media Ltd | Information & communication | 2022 |
| Offshore Matters Limited | Professional & scientific | 2026 |
| Offshore Safety Solutions Limited | Administrative & support | 2014 |
| OFI Limited | Wholesale & retail | 2012 |
| OFL Holdings Limited | Financial services | 2025 |
| Oflaz Furniture Textile Ltd | Wholesale & retail | 2026 |
| Ofs(North West) Ltd | Construction | 2016 |
| Ogaye Care Support Ltd | Health & social care | 2025 |
| OGB Group Ltd | Real estate | 2023 |
| Ogden OIL & GAS Services Ltd | Manufacturing | 2011 |
| OGP Materials Consultants Limited | Professional & scientific | 2022 |
| Ogre Software Ltd. | Information & communication | 2018 |
| Ogugu IT Services Limited | Information & communication | 2022 |
| OH Beehive Ltd | Construction | 2025 |
| OH Consulting Group Limited | Professional & scientific | 2023 |
| OH Motion Studio Limited | Professional & scientific | 2026 |
| OH My Dubai Ltd | Administrative & support | 2018 |
| OH My Glaze the Sauce Limited | Wholesale & retail | 2020 |
| OH Physiotherapy North West Ltd | Health & social care | 2019 |
| OH SO Socials Creative Ltd | Professional & scientific | 2026 |
| OH Sugar Dessert Parlour Ltd | Hospitality | 2024 |
| OH Technology Ltd | Information & communication | 2019 |
| OH Telecom Ltd | Construction | 2019 |
| OH This Way Ltd | Other services | 2018 |
| OH2U Ltd | Public administration | 2024 |
| OHA Property Limited | Real estate | 2022 |
| Ohare Rental Ltd | Real estate | 2026 |
| OHF Property Ltd | Transport & logistics | 2022 |
| OHG Construction & Design Solutions Limited | Construction | 2025 |
| Ohmg Group Ltd | Manufacturing | 2026 |
| Oikos Residential Ltd | Real estate | 2025 |
| OIL & GAS Tech Company Limited | Other services | 2011 |
| OIL Salvage Limited | Manufacturing | 1984 |
| OIL Technics (Fire Fighting Products) Limited | Professional & scientific | 1992 |
| OIL Technics Holdings Limited | Professional & scientific | 1997 |
| OIL Technics Limited | Manufacturing | 1987 |
| Oirpacid Ltd | Construction | 2026 |
| Oisf Electrical Limited | Construction | 2026 |