| Ockham Publishing Group Limited | Information & communication | 2017 |
| Octagon Property Development Limited | Real estate | 2008 |
| Octavio Group Limited | Financial services | 2023 |
| Octavio Partnership Limited | Professional & scientific | 2004 |
| Octonexus Power Ltd | Professional & scientific | 2025 |
| Octopus Test Systems Ltd | Professional & scientific | 2018 |
| Ocube Engineering Consulting Ltd | Professional & scientific | 2019 |
| Oculus Safe-Well Consultancy Limited | Professional & scientific | 2017 |
| OD Project Solutions Ltd | Administrative & support | 2012 |
| Odeon Impex LP | | 2014 |
| Odfjell Drilling Shetland Ltd | Mining & quarrying | 2009 |
| Odfjell Drilling South Africa Ltd. | Administrative & support | 2016 |
| Odfjell Oceanwind PD UK Ltd | Financial services | 2025 |
| Odfjell Technology (UK) Ltd. | Administrative & support | 2002 |
| Odfjell Well Services (UK) Ltd | Administrative & support | 2015 |
| ODS ABZ Limited | Hospitality | 2017 |
| ODX Innovations Limited | Professional & scientific | 2016 |
| Odyssey Experience Ltd | Health & social care | 2023 |
| Oella Consulting Limited | Information & communication | 2017 |
| OEM Group (Scotland) Limited | Wholesale & retail | 2012 |
| Oeoiiatastes Limited | Hospitality | 2016 |
| OFF Limits Clothing Limited | Wholesale & retail | 2025 |
| Offshore Agility Ltd | Professional & scientific | 2019 |
| Offshore Compliance Training Ltd | Professional & scientific | 2026 |
| Offshore Opex Ltd | Transport & logistics | 2016 |
| Offshore Projects Alliance Ltd | Professional & scientific | 2017 |
| Offshore Rescue & Crisis Aviation SAR CIC | Transport & logistics | 2026 |
| Offshore Support Vessels IX Limited | Mining & quarrying | 1999 |
| Offshore Support Vessels VI Limited | Mining & quarrying | 2007 |
| Offshore Support Vessels VII Limited | Mining & quarrying | 2007 |
| Offshore Training Foundation | Education | 2002 |
| Offshore Welding Services Ltd | Professional & scientific | 2023 |
| OGA Engineering Ltd | Professional & scientific | 2018 |
| Ogenus Offshore Management UK Ltd | Administrative & support | 2023 |
| Ogilvie Geoscience Limited | Mining & quarrying | 2016 |
| Ogilvie Solutions Ltd | Professional & scientific | 2015 |
| Ogilvielegal Ltd | Professional & scientific | 2016 |
| Ogse Ltd | Real estate | 2026 |
| Ogtc Limited | Professional & scientific | 2020 |
| OGV Group Ltd | Professional & scientific | 2020 |
| OGV Studio Ltd | Professional & scientific | 2023 |
| OGV Taproom Global Limited | Financial services | 2022 |
| OGV XL Limited | Manufacturing | 2016 |
| OH Scotland Ltd | Wholesale & retail | 2023 |
| Oh-Kay Driving Ltd | Education | 2023 |
| OIL & GAS Legal Limited | Professional & scientific | 2014 |
| OIL & GAS Process Services Ltd | Mining & quarrying | 2024 |
| OIL and GAS Management Consulting Limited | Administrative & support | 2009 |
| OIL and GAS Soft Skills Limited | Professional & scientific | 2013 |
| OIL States Industries (UK) Limited | Mining & quarrying | 1996 |
| Oildynamix Ltd | Mining & quarrying | 2013 |
| Oilenco Limited | Manufacturing | 2008 |
| Oilfield Equipment Supplies Limited | Wholesale & retail | 2025 |
| Oilfield Production Enhancement Consulting Services Limited | Professional & scientific | 2016 |
| Oilfield Project Services Ltd | Information & communication | 2013 |
| Oilfield Technical Services Limited | Professional & scientific | 2013 |
| Oilgen Ltd | Professional & scientific | 2002 |
| Oiltube Limited | Wholesale & retail | 1995 |
| OIM Offshore Services Ltd | Professional & scientific | 2025 |
| Oiya Limited | Real estate | 2022 |
| OK Express Limited | Transport & logistics | 2022 |
| Okunade Group Ltd | Wholesale & retail | 2026 |
| OLA Oloruntemi Limited | Transport & logistics | 2024 |
| Olaalaa Ltd | Wholesale & retail | 2026 |
| Olak Services Ltd | Information & communication | 2025 |
| Olaks Consultancy Ltd | Information & communication | 2017 |
| Olayo Ltd | Wholesale & retail | 2025 |
| Old Aberdeen Counselling Services Limited | Professional & scientific | 2012 |
| Old Aberdeen Townhouse Ltd | Hospitality | 2022 |
| Old Compton Associates Limited | Administrative & support | 2015 |
| Old Machar Medical Practice LLP | | 2024 |
| Old Mart Cleaning Company Limited | Other services | 2024 |
| Oldmachar OUT of School Clubs Ltd | Health & social care | 2011 |
| Oldmeldrum Properties Limited | Real estate | 2014 |
| Oldtown Farm Limited | Agriculture & fishing | 2026 |
| Oleochem Project Management Limited | Administrative & support | 2004 |
| Oleum Analytics Limited | Mining & quarrying | 2023 |
| OLH Services Ltd | Professional & scientific | 2017 |
| Olibran Ltd | Professional & scientific | 2014 |
| Olive and Honey Homes Limited | Real estate | 2017 |
| Olive Barn Ltd | Hospitality | 2025 |
| Olive Gold Group Ltd | Wholesale & retail | 2025 |
| Olive Healthcare Solutions (Manchester) Ltd | Health & social care | 2017 |
| Olive Property Leasing Ltd | Real estate | 2026 |
| Oliveoaks Consulting Ltd | Professional & scientific | 2025 |
| Olives Clinical Services Ltd | Health & social care | 2026 |
| Olives Tree for OIL and GAS Engineering & Services Limited | Wholesale & retail | 2014 |
| Olly's Materials Services Ltd | Mining & quarrying | 2018 |
| Olly’S Comics Ltd | Wholesale & retail | 2025 |
| Olsthoorn Ltd | Education | 2023 |
| Olubola Cars Limited Ltd | Wholesale & retail | 2020 |
| Olyke Limited | Hospitality | 2009 |
| Olympus Autobody Limited | Wholesale & retail | 2019 |
| Om'Gg Limited | Wholesale & retail | 2016 |
| OMA Luxe Ltd | Wholesale & retail | 2025 |
| Omatron Limited | Real estate | 2005 |
| Omax Nature LP | | 2013 |
| Omega Completion Limited | Manufacturing | 2014 |
| Omega Geoservices and Consultancy Limited | Mining & quarrying | 2014 |
| Omega Integrity Solutions Limited | Professional & scientific | 2021 |