| Old Town Centre Ltd | Hospitality | 2020 |
| Oldalbion Ltd | Financial services | 2014 |
| Oldbridge Import L.P. | | 2015 |
| Oldcross Trans L.P. | | 2015 |
| Oliphant Bakers Limited | Manufacturing | 2005 |
| Olive Property Management Limited | Other services | 2017 |
| Olive Retreat With AVA Ltd | Wholesale & retail | 2026 |
| Olive Tree Houses Limited | Real estate | 2015 |
| Olivia Cameron Bridal Limited | Wholesale & retail | 2008 |
| Olivier Properties Ltd | Real estate | 2022 |
| Ollie and Forbes Ltd | Professional & scientific | 2004 |
| OMC Dundee Ltd | Hospitality | 2025 |
| Omebb Property Ltd | Real estate | 2021 |
| Omega IT Limited | Information & communication | 2023 |
| Omegan Capital LP | | 2017 |
| Omer Turgul Ltd | Hospitality | 2026 |
| Omnai Tech Limited | Information & communication | 2023 |
| Omni Instruments Limited | Professional & scientific | 2002 |
| Omni Supplies Ltd | Wholesale & retail | 2012 |
| Omnia Express L.P. | | 2015 |
| Omnipro Solutions Ltd | Manufacturing | 2026 |
| Omnis Properties Ltd | Real estate | 2019 |
| Omnitrade Logistic L.P. | | 2015 |
| ON Point Management Ltd | Professional & scientific | 2018 |
| ON the Rise Properties Ltd | Real estate | 2022 |
| Onda Hospitality Consultancy Limited | Professional & scientific | 2026 |
| One Accord Ltd | Health & social care | 2026 |
| One Best Move Ltd | Real estate | 2023 |
| One Crew Social Network (UK) Limited | Professional & scientific | 2024 |
| One Peak Ltd | Arts & recreation | 2024 |
| One Solution Property Management Limited | Real estate | 2016 |
| ONE2ONE Retail Ltd | Wholesale & retail | 2024 |
| Onesphereco Ltd | Wholesale & retail | 2026 |
| Onesystem Production LP | | 2017 |
| Ongk L.P. | | 2011 |
| Onlineproshops Ltd | Wholesale & retail | 2026 |
| Only Click Ltd | Wholesale & retail | 2019 |
| Only Doors & Windows Limited | Other services | 2018 |
| Only Fitness Gear Ltd | Wholesale & retail | 2022 |
| Onorach Innovation Limited | Information & communication | 2015 |
| Onside Impacts CIC | Hospitality | 2025 |
| Onsite Flooring Limited | Construction | 1999 |
| Onsun Logistics LP | | 2017 |
| Onyx Asset Management Limited | Real estate | 2016 |
| Onyx-Company Limited | Extraterritorial | 2022 |
| OOA1 Ltd | Hospitality | 2024 |
| Ooab Limited | Hospitality | 2023 |
| Ooabb Ltd | Hospitality | 2025 |
| Ooft Internet Ltd | Information & communication | 2023 |
| Oogsta Limited | Information & communication | 2018 |
| Oojoo Connect Ltd | Transport & logistics | 2026 |
| OOR Energy Ltd | Professional & scientific | 2024 |
| Open Close CIC | Arts & recreation | 2020 |
| Open Door Finance Limited | Financial services | 2025 |
| Open Doors Services Ltd | Construction | 2025 |
| Openroll Sales LP | | 2017 |
| Opmgc Limited | Hospitality | 2019 |
| Opporchancity Knocks Ltd | Professional & scientific | 2026 |
| Oppulent Ventures Ltd | Wholesale & retail | 2023 |
| Optimal Glazing Solutions Ltd | Administrative & support | 2023 |
| Optimise Investments UK Ltd | Real estate | 2022 |
| Optimise Outreach Ltd | Information & communication | 2023 |
| Optom Services Ltd | Health & social care | 2018 |
| Opulentpetro Ltd | Administrative & support | 2025 |
| Oracle Car Sales Limited | Wholesale & retail | 2012 |
| Orange Penguin ICT Ltd | Information & communication | 2022 |
| Orca Cleaning Ltd | Administrative & support | 2023 |
| Orchar Kitchens & Bathrooms Ltd | Construction | 2018 |
| Orchard Park Dental Practice Limited | Health & social care | 2013 |
| Orchid Grove Limited | Other services | 2019 |
| Ordep Logistics Limited | Administrative & support | 2006 |
| Orderstar L.P. | | 2016 |
| Oria-Sleep Ltd | Manufacturing | 2026 |
| Orion Security Systems Ltd | Administrative & support | 2025 |
| Orion Vacation Homes Ltd | Real estate | 2025 |
| Ornits Ltd | Wholesale & retail | 2024 |
| Orotava Concepts Ltd | Real estate | 2026 |
| Orrin Property Ltd | Real estate | 2024 |
| Orso Ventures Limited | Professional & scientific | 2022 |
| Orthopaedic Pillars Ltd | Health & social care | 2023 |
| Osborne GUN Company Limited | Administrative & support | 2010 |
| Osborne Terrace Limited | Real estate | 2006 |
| Oscar Dundee Barber Limited | Other services | 2024 |
| OSG Hair Ltd | Other services | 2021 |
| Oshibori Dundee Ltd | Hospitality | 2017 |
| Oshibori Scotland Ltd | Hospitality | 2014 |
| Osprey Electric Ltd | Manufacturing | 2018 |
| Osprey Park Properties Ltd | Real estate | 2022 |
| Ossian Hosting Ltd | Information & communication | 2021 |
| Ossian Media Ltd | Information & communication | 2023 |
| Ostan Hotel Group Ltd | Hospitality | 2020 |
| Ostara Scotland Limited | Financial services | 2024 |
| Ostberg Sales L.P. | | 2009 |
| Oswald Pattie (Tayport) Limited | Real estate | 1959 |
| Other Label Clothing Ltd | Wholesale & retail | 2017 |
| OTK UK Ltd | Professional & scientific | 2016 |
| Otorgar Limited | Real estate | 2023 |
| Otterly Awesome Collectibles Ltd | Wholesale & retail | 2026 |
| OUR Lovely Goods Ltd | Wholesale & retail | 2020 |
| OUR Project Limited | Professional & scientific | 2009 |