| Optima Conception LP | | 2017 |
| Optima Employee Benefit Consultants Ltd | Financial services | 1998 |
| Optima Property (Edinburgh) Limited | Real estate | 2018 |
| Optima Trading L.P. | | 2015 |
| Optimaise Intelligence Ltd | Information & communication | 2026 |
| Optimal Economics Limited | Professional & scientific | 2009 |
| Optimal Health Chiropractic Limited | Administrative & support | 2009 |
| Optimal M&E Project Services Ltd | Professional & scientific | 2024 |
| Optimal Simplicity Limited | Information & communication | 2019 |
| Optimal Utility Limited | Construction | 2016 |
| Optimal Welding and Fabrication Ltd | Manufacturing | 2021 |
| OPTIMAL8 Ltd. | Other services | 2016 |
| Optimax Products LP | | 2013 |
| Optime Consulting Services Limited | Administrative & support | 2014 |
| Optimise Adhd Limited | Health & social care | 2025 |
| Optimise Design Limited | Information & communication | 2005 |
| Optimise Holdings Limited | Information & communication | 2005 |
| Optimise Mortgage Solutions Ltd | Financial services | 2021 |
| Optimise Solutions Limited | Information & communication | 1989 |
| Optimise Web Limited | Information & communication | 2005 |
| Optimise Your Potential Limited | Administrative & support | 2013 |
| Optimised Environments (Manchester) Limited | Professional & scientific | 2017 |
| Optimised Environments Limited | Professional & scientific | 2009 |
| Optimistic International LP | | 2016 |
| Optimize Access, L.P. | | 2016 |
| Optimos Performance Ltd | Information & communication | 2025 |
| Optimum Dexterity Ltd | Real estate | 2017 |
| Optimum Trading Ltd | Wholesale & retail | 2019 |
| Optimum Wind Services, Ltd. | Construction | 2025 |
| Optimvestment Ltd | Financial services | 2021 |
| Optinex Digital Limited | Information & communication | 2025 |
| Optinexis Limited | Wholesale & retail | 2025 |
| Option Office LP | | 2015 |
| Option Properties (Scotland) Ltd. | Real estate | 2010 |
| Opto Advisory Limited | Professional & scientific | 2018 |
| Opto Trade L.P. | | 2013 |
| Optosense Ltd | Professional & scientific | 2024 |
| Optovise Limited | Professional & scientific | 2010 |
| Optp Food Limited | Hospitality | 2023 |
| Optravel Ltd | Transport & logistics | 2024 |
| Optrust Scots I Limited | Administrative & support | 2011 |
| Opulent Catering Limited | Wholesale & retail | 2017 |
| Opus Magnum Vocat NOS Ltd | Information & communication | 2017 |
| Opus Soft LP | | 2018 |
| OQ Consultancy Ltd | Professional & scientific | 2026 |
| Oqoodi Ltd | Information & communication | 2024 |
| ORA Care Solutions Limited | Professional & scientific | 2019 |
| ORA Financial Solutions Limited | Professional & scientific | 2026 |
| ORA Prive Limited | Other services | 2018 |
| Oracare (Scotland) Limited | Real estate | 2018 |
| Oral Surgery Services Ltd | Health & social care | 2023 |
| Oran Consulting Ltd | Professional & scientific | 2012 |
| Oran Finance Limited | Financial services | 1973 |
| Oran NA Mara Ltd | Professional & scientific | 2020 |
| Orange Flame Traders LP | | 2015 |
| Orange Fruit for Trading Ltd | Wholesale & retail | 2024 |
| Orange IVY Ltd | Professional & scientific | 2019 |
| Orange Matter Limited | Information & communication | 2020 |
| Orangedale Investments | | 2001 |
| Orangio Trading LP | | 2017 |
| Orangutan Projects Ltd | Professional & scientific | 2022 |
| ORB Verify Ltd | Information & communication | 2024 |
| Orbanesa SP | | 2003 |
| Orbest Investments LP | | 2012 |
| Orbin Invest LP | | 2017 |
| Orbin Management LP | | 2015 |
| Orbin Trading LP | | 2018 |
| Orbis Enterprises Limited | Real estate | 2010 |
| Orbis Technologies Ltd | Information & communication | 2008 |
| Orbisai-Labs Limited | Information & communication | 2026 |
| Orbista Europen LP | | 2016 |
| Orbit Creative Technologies Ltd | Information & communication | 2025 |
| Orbit Shift Media Ltd | Professional & scientific | 2024 |
| Orbital Sound Design | | 1993 |
| Orbithost Limited | Professional & scientific | 2000 |
| Orbitin SP | | 2001 |
| Orbitl Tech Ltd | Information & communication | 2024 |
| Orbitonix Ltd | Professional & scientific | 2019 |
| Orbiz Services LP | | 2016 |
| Orby Trading LP | | 2013 |
| Orchard Alliance LP | | 2016 |
| Orchard Automotives Limited | Wholesale & retail | 2020 |
| Orchard Brae (Edinburgh) Flats Limited | Real estate | 1971 |
| Orchard Brae Services Ltd | Construction | 2026 |
| Orchard Childcare Training Limited | Education | 2020 |
| Orchard Independent Limited | Financial services | 2009 |
| Orchard Lane Holdings LP | | 2016 |
| Orchard Street Founder Partner II LP | | 2012 |
| Orchard Street Founder Partner LP | | 2008 |
| Orchard Street UK Prime Property GP NO.2 Limited | Real estate | 2014 |
| Orchard Street UK Prime Property GP NO.3 Limited | Real estate | 2015 |
| Orchard Street UK Prime Property GP NO.4 Limited | Real estate | 2016 |
| Orchard Street UK Prime Property NO.3 LP | | 2015 |
| Orchard Street UK Prime Property NO.4 LP | | 2016 |
| Orchard Street UK Prime Property NO2 LP | | 2014 |
| Orchard Valley Ltd | Real estate | 2025 |
| Orchid Solar Limited | Professional & scientific | 2025 |
| Orde Cafes Limited | Hospitality | 2017 |
| Ordelmira Pathworks Ltd | Wholesale & retail | 2026 |
| Order on BOT Limited | Information & communication | 2023 |