| Oliver Cowan Events Limited | Arts & recreation | 2024 |
| Oliver Edward Limited | Professional & scientific | 1995 |
| Oliver Group Holdings Ltd | Financial services | 2025 |
| Oliver James Farrell Limited | Information & communication | 2015 |
| Oliver LEE Trading Limited | Hospitality | 2007 |
| Oliver Logistic Solutions Ltd | Transport & logistics | 2023 |
| Oliver Plant & Maintenance Limited | Manufacturing | 2014 |
| Oliver Wright Services Limited | Professional & scientific | 2015 |
| Oliver's Homes and Development Ltd | Real estate | 2022 |
| Olives and Sweet Ltd | Hospitality | 2024 |
| Olivia & Papa Ltd | Health & social care | 2015 |
| Olivia Dennison Ltd | Health & social care | 2021 |
| Olivia Gotuje Ltd | Hospitality | 2026 |
| Olivia Kate Dental Care Limited | Health & social care | 2024 |
| Olivia Mitchell Developments Limited | Real estate | 2023 |
| Olivia's Edit Limited | Wholesale & retail | 2023 |
| Olivia's Tree Limited | Education | 2024 |
| Ollie Burman Coach Ltd | Health & social care | 2018 |
| Ollie Watson Ltd | Transport & logistics | 2026 |
| Ollo Farmers Market Limited | Wholesale & retail | 2024 |
| Ollo Padel Limited | Arts & recreation | 2025 |
| OLM Masonry Works Limited | Construction | 2026 |
| OLM Network Solutions Ltd | Construction | 2022 |
| Olnifa Ltd | Health & social care | 2022 |
| Ologist Ltd | Information & communication | 2022 |
| Olos Records Ltd | Information & communication | 2023 |
| Olsp Ltd | Extraterritorial | 2017 |
| Olstat Ltd | Wholesale & retail | 2026 |
| Olto Digital Publishing Ltd | Information & communication | 2025 |
| Olwyn FOX (2000) Limited | Construction | 1999 |
| Olymerl Ltd | Health & social care | 2022 |
| Olympia and Bath Ltd. | Real estate | 2017 |
| Olympia Park Developments Limited | Extraterritorial | 2018 |
| Olympia Projects Limited | Construction | 2013 |
| Olympia Supplies Limited | Wholesale & retail | 2015 |
| Olympia Urns & Vases Ltd | Manufacturing | 2013 |
| Olympian Heights Limited | Households | 1994 |
| Olympic Financial Consultants Limited | Extraterritorial | 1995 |
| Olympic Management Limited | Administrative & support | 1988 |
| Olympix Media Ltd | Information & communication | 2023 |
| OM Digital Limited | Information & communication | 2020 |
| OM Electrical & General Building Ltd | Construction | 2025 |
| OM Flowers Ltd | Wholesale & retail | 2016 |
| OM Shah Ltd | Real estate | 2024 |
| Omac Design Ltd | Manufacturing | 2022 |
| Omade Ltd | Hospitality | 2019 |
| Oman Garbix Limited | Information & communication | 2013 |
| Omanior Ltd | Wholesale & retail | 2026 |
| Omar Finance Limited | Financial services | 2012 |
| Omar Khemoudj Limited | Professional & scientific | 2017 |
| Omar Propco Ltd | Real estate | 2013 |
| Omar Shawarma Ltd | Hospitality | 2026 |
| Omarco Construction Services Limited | Construction | 2015 |
| Omaris World Logistics Limited | Transport & logistics | 2026 |
| OMB (GB) Limited | Wholesale & retail | 2011 |
| Ombm Ltd | Other services | 2018 |
| Ombo AI Ltd | Information & communication | 2023 |
| OMC (UK) Limited | Professional & scientific | 2014 |
| OME Transformations Limited | Construction | 2025 |
| Omech Mechanical Services Ltd | Construction | 2024 |
| Omeeo Ltd | Real estate | 2019 |
| Omega Auamo Ltd | Financial services | 2023 |
| Omega Contracts Limited | Administrative & support | 2014 |
| Omega Design UK Limited | Manufacturing | 1987 |
| Omega Electrical Contractors Ltd | Construction | 2023 |
| Omega Films Ltd. | Information & communication | 2012 |
| Omega Health Group Ltd. | Health & social care | 2016 |
| Omega Legal Services Limited | Information & communication | 1990 |
| Omega Renovations Ltd | Construction | 2025 |
| Omega Signs Limited | Manufacturing | 1992 |
| Omegawolf Limited | Wholesale & retail | 2024 |
| Omeri Construction Ltd | Construction | 2024 |
| Omg.Event.Uk Limited | Administrative & support | 2026 |
| Omis Investment Limited | Administrative & support | 2025 |
| Omkoppla Limited | Education | 2025 |
| Omni Bazaar Ltd | Wholesale & retail | 2024 |
| Omni Beauty Ltd | Other services | 2019 |
| Omni Business Consulting Ltd | Professional & scientific | 2023 |
| Omni Essentials Ltd | Wholesale & retail | 2025 |
| Omni Plumbing and Heating Ltd | Construction | 2016 |
| Omnia Leeds Ltd | Real estate | 2023 |
| Omnia NIX Law Limited | Professional & scientific | 2026 |
| Omnia NIX Ltd | Administrative & support | 2025 |
| Omnicleans Ltd | Administrative & support | 2022 |
| Omnipay Solutions Ltd | Professional & scientific | 2026 |
| Omnitech Software Ltd | Information & communication | 2015 |
| Omniunus Limited | Extraterritorial | 2020 |
| Omoigui Ltd | Extraterritorial | 2018 |
| Omojo Services Ltd | Administrative & support | 2020 |
| Omor Group Ltd | Construction | 2025 |
| Omorfi Skincare Ltd | Extraterritorial | 2026 |
| Omoritech Group Ltd | Information & communication | 2025 |
| OMP Ltd | Professional & scientific | 2024 |
| OMR Plumbing Limited | Construction | 2022 |
| OMR Property Solutions Ltd | Real estate | 2024 |
| Omsi Ltd | Professional & scientific | 2021 |
| Omsyms Limited | Professional & scientific | 2016 |
| OMY Imaging and Clinical Services Ltd | Wholesale & retail | 2025 |
| ON Board Construction Ltd | Construction | 2024 |
| ON Point Reviews Ltd | Wholesale & retail | 2018 |