| Olexis Limited | Wholesale & retail | 2026 |
| OLI Sausage Ltd | Extraterritorial | 2011 |
| Olibelle Group Limited | Financial services | 2023 |
| Olima Limited | Financial services | 2024 |
| Olimp Ltd | Construction | 2015 |
| Olinea Rose Ltd | Other services | 2024 |
| Olio Pizza Box Ltd | Hospitality | 2025 |
| Olisa Ltd | Professional & scientific | 2025 |
| Olive Accommodation Ltd | Hospitality | 2024 |
| Olive and Apple Limited | Hospitality | 2018 |
| Olive Branch Home Care Limited | Health & social care | 2022 |
| Olive Branch Housing Ltd | Health & social care | 2024 |
| Olive Building Contractors Ltd | Construction | 2025 |
| Olive Dental Practice Limited | Health & social care | 2009 |
| Olive Frontier Care Services Ltd | Health & social care | 2026 |
| Olive Homecare Ltd | Other services | 2013 |
| Olive IT Solutions Ltd | Information & communication | 2025 |
| Olive Properties Consultants Limited | Real estate | 2004 |
| Olive Tree Communications Limited | Information & communication | 2019 |
| Olive Tree Media Limited | Manufacturing | 2023 |
| Olivecare Medical Ltd | Health & social care | 2025 |
| Oliver C Anderson (Holdings) Limited | Real estate | 1963 |
| Oliver Hind Limited | Construction | 2023 |
| Oliver House (Kirk Hallam) Ltd | Health & social care | 2019 |
| Oliver Interiors Limited | Construction | 2018 |
| Oliver Jones Associates Limited | Financial services | 2001 |
| Oliver Knight Property Management and Development Ltd | Real estate | 2025 |
| Oliver Tree Limited | Wholesale & retail | 2025 |
| Olivia Aspinall Studio Limited | Professional & scientific | 2019 |
| Olivia Josephine Care Limited | Health & social care | 2009 |
| Olivia Reign Ltd | Wholesale & retail | 2021 |
| Olivialily Cleaning Ltd | Administrative & support | 2023 |
| Olivialily Domestic Cleaning Limited | Administrative & support | 2025 |
| Oliviavs Ltd | Real estate | 2022 |
| Olivier Wallace Limited | Wholesale & retail | 2024 |
| Olixo Limited | Wholesale & retail | 2026 |
| Olkun Property Investment Limited | Real estate | 2024 |
| Ollerton Motorcross Club Ltd. | Other services | 1989 |
| Ollie Driver Limited | Other services | 2011 |
| Olly Hunter Ltd | Professional & scientific | 2022 |
| Olly Services Ltd | Health & social care | 2019 |
| Ollys Pilot Vehicles Ltd | Transport & logistics | 2026 |
| Olmaa Ltd | Professional & scientific | 2024 |
| Olufam Ltd | Real estate | 2022 |
| Olympia Hatcheries Limited | Agriculture & fishing | 2024 |
| Olympic Embroidery Limited | Manufacturing | 1988 |
| Olympic Shaver Centre Limited | Wholesale & retail | 1976 |
| Olympus Cars Ltd | Wholesale & retail | 2023 |
| Olympus Property Holdings Limited | Real estate | 2020 |
| OM Estates Management Ltd | Real estate | 2020 |
| OM SRI Enterprise Ltd | Wholesale & retail | 2026 |
| Omac Healthcare Ltd | Health & social care | 2023 |
| Omannels Limited | Wholesale & retail | 2019 |
| Omar Nawaz Property Holding Ltd | Real estate | 2025 |
| OMC Joinery Limited | Manufacturing | 2001 |
| Omead Homes Ltd | Health & social care | 2023 |
| Omega Construction Services Ltd | Construction | 2012 |
| Omega Home Improvements Ltd | Manufacturing | 2018 |
| Omega Lining Services Ltd | Construction | 2021 |
| Omega Lining Solutions Limited | Wholesale & retail | 2018 |
| Omega Lofts Limited | Construction | 2012 |
| Omega Red Holdings Limited | Professional & scientific | 2007 |
| Omega Refurb and Development Ltd | Real estate | 2020 |
| Omega Resource Group Limited | Extraterritorial | 1998 |
| Omega Scaffold Ltd | Construction | 2014 |
| Omegs Cleaning Services Limited | Administrative & support | 2025 |
| Omegs Estate Ltd | Real estate | 2025 |
| Omegs-Uk Limited | Health & social care | 2011 |
| OMF Consult Ltd | Professional & scientific | 2024 |
| OMF Electrical Ltd | Construction | 2015 |
| OMG Burgur Ltd | Hospitality | 2024 |
| OMG Nottingham Limited | Arts & recreation | 2019 |
| Omid Barber Ltd | Other services | 2025 |
| Omiji International Trading Ltd | Wholesale & retail | 2015 |
| Omina Project Management Ltd | Professional & scientific | 2023 |
| Omit Engineering Ltd | Manufacturing | 2025 |
| Omitan Ltd | Manufacturing | 2023 |
| Omkar Properties Limited | Real estate | 2020 |
| Omni Crocus Limited | Construction | 2019 |
| Omni Developments Limited | Construction | 2015 |
| Omni Direction (UK) Ltd. | Professional & scientific | 1996 |
| Omni Freehold Limited | Construction | 2014 |
| Omni Professional Ltd | Administrative & support | 2025 |
| Omnia Property Investments Limited | Construction | 2022 |
| Omnia Sourcing Ltd | Wholesale & retail | 2025 |
| Omnia(Cs) Limited | Wholesale & retail | 2004 |
| Omnifactory Limited | Manufacturing | 2025 |
| Omnigo Ltd | Construction | 2014 |
| Omnika Commerce Ltd | Wholesale & retail | 2025 |
| Omnilongevity Ltd | Arts & recreation | 2026 |
| Omninomad Limited | Information & communication | 2023 |
| Omnipotent Limited | Health & social care | 2016 |
| Omnisec Ltd | Construction | 2017 |
| Omonstony Photography Ltd | Professional & scientific | 2018 |
| Omosapiens.Xy Ltd | Information & communication | 2026 |
| Omuk Group Limited | Financial services | 2026 |
| Omvandla Group Limited | Other services | 2023 |
| OMW Developments Limited | Construction | 2025 |
| OMW Ltd | Wholesale & retail | 2017 |
| OMW Solutions Ltd | Information & communication | 2015 |