| Onestopheadshop Ltd | Wholesale & retail | 2025 |
| Oneworld Technology Adept LP | | 2016 |
| Onex Corporation L.P. | | 2010 |
| One’S & Two’S Solutions Ltd | Construction | 2025 |
| Onfiden Marketing LP | | 2012 |
| Ongen Limited | Information & communication | 2014 |
| Onigiri & Soup Ltd | Hospitality | 2022 |
| Online Concept Solutions LP | | 2015 |
| Online E Business Ltd | Wholesale & retail | 2020 |
| Online Heaven Ltd | Wholesale & retail | 2023 |
| Online Mayfield Scotland LLP | | 2016 |
| Online Partners LP | | 2021 |
| Online Point LP | | 2014 |
| Online Power Services LP | | 2016 |
| Online Savers Limited | Wholesale & retail | 2025 |
| ONLINEPAYMENT24 LP | | 2015 |
| Only Conception LP | | 2016 |
| Only YU Ltd | Hospitality | 2024 |
| Onnuri Ltd | Hospitality | 2016 |
| Onred Productions Ltd | Information & communication | 2018 |
| Onshore to Offshore Training Services Ltd | Transport & logistics | 2019 |
| Onslow & Maria LP | | 2023 |
| Onslow Allied LP | | 2015 |
| Ontario International LP | | 2003 |
| Ontario Investments SP | | 2000 |
| Ontario Real Estate LP | | 2011 |
| Onto Coffee Limited | Hospitality | 2025 |
| Ontrac Energy Limited | Real estate | 2012 |
| Onwards Travel Ltd | Transport & logistics | 2026 |
| Onwe Holdings Ltd | Real estate | 2022 |
| Onwe Properties Ltd | Real estate | 2024 |
| Onyx 9 Ltd | Real estate | 2026 |
| Onyx Assets LLP | | 2018 |
| Onyx Capital Ltd | Hospitality | 2017 |
| Onyx Facilities Management Ltd | Households | 2025 |
| Onyx Global Exploration LP | | 2017 |
| Onyx Interiors Edinburgh Ltd | Professional & scientific | 2024 |
| Onyx Pro Ltd | Real estate | 2025 |
| Onyx Safety Engineering Limited | Professional & scientific | 2019 |
| Onyx Scotland Ltd | Wholesale & retail | 2026 |
| Onyx Security Group Ltd | Financial services | 2025 |
| Onyx Virtual Assistant Ltd | Administrative & support | 2023 |
| Onyx Wealth Group Limited | Professional & scientific | 2019 |
| OOF Animation Ltd | Arts & recreation | 2024 |
| OOH My Nails Limited | Other services | 2019 |
| OOH! Ruby Shoes Limited | Wholesale & retail | 2007 |
| OOO A.T.K. LP | | 2016 |
| OOR Cooinda Limited | Manufacturing | 2024 |
| Ootnoo Ltd | Water & waste | 2016 |
| OP Consulting Limited | Professional & scientific | 2003 |
| Opal Dents Limited | Health & social care | 2025 |
| Opal Investments LP | | 2016 |
| Opal Project Solutions Ltd | Households | 2025 |
| Opal Trade LP | | 2016 |
| Opalfire Consultancy Limited | Professional & scientific | 2005 |
| OPC Industries Ltd | Information & communication | 2019 |
| OPE Digital LP | | 2015 |
| Open Arms Group CIC | Hospitality | 2025 |
| Open Arms Group Edinburgh Limited | Hospitality | 2025 |
| Open Cleaner Company Limited | Administrative & support | 2025 |
| Open Door Productions Ltd | Arts & recreation | 2018 |
| Open Europe Export L.P. | | 2014 |
| Open EYE Gallery Edinburgh Limited | Arts & recreation | 2012 |
| Open Fringe C.I.C. | Arts & recreation | 2025 |
| Open Generation Developments LP | | 2015 |
| Open Inn Ltd | Hospitality | 2019 |
| Open Investments L.P. | | 2013 |
| Open Safety Equipment Limited | Manufacturing | 2008 |
| Open Services L.P. | | 2012 |
| Open Technology Support L.P. | | 2013 |
| Openculinary C.I.C. | Information & communication | 2019 |
| Opentable Scottish Limited Partnership | | 2012 |
| Opentech Resources LP | | 2015 |
| Operability Limited | Administrative & support | 2020 |
| Operactive Arts Ltd | Wholesale & retail | 2024 |
| Operanter Group LP | | 2019 |
| Operational Excellence (Opex) Group Ltd | Professional & scientific | 2010 |
| Operenza Governance Limited | Information & communication | 2026 |
| Opergy Scotland Limited | Professional & scientific | 2020 |
| Operis Apps Ltd | Information & communication | 2026 |
| Operqora Tools Limited | Information & communication | 2026 |
| Operra Ltd | Information & communication | 2026 |
| Opex Ltd. | Health & social care | 1998 |
| OPG-4 UK Limited | Arts & recreation | 2018 |
| Opinew Limited | Information & communication | 2015 |
| Opium Events Limited | Hospitality | 2026 |
| OPM Trading LP | | 2018 |
| Opmodal Ltd | Information & communication | 2020 |
| OPR Consultancy Ltd | Professional & scientific | 2023 |
| Oprea Development Corporation LP | | 2011 |
| OPT Electronics LP | | 2013 |
| Optab Limited | Information & communication | 2023 |
| Opteam Ltd | Professional & scientific | 2025 |
| Optegris Ltd | Professional & scientific | 2025 |
| Optibright Ltd | Wholesale & retail | 2020 |
| Optical and Fashion Glasses Representatives and Co | | 1992 |
| Optical Lighting Limited | Construction | 2007 |
| Opticare Direct Ltd | Wholesale & retail | 2023 |
| Opticare Scotland Ltd | Wholesale & retail | 2023 |
| Optiloft LP | | 2014 |