| OBT Trans Ltd | Transport & logistics | 2018 |
| Obvs Ltd | Manufacturing | 2020 |
| OC Composite Consulting Ltd | Professional & scientific | 2018 |
| OC Haulage Ltd | Transport & logistics | 2015 |
| Occamesis Limited | Manufacturing | 2012 |
| Occasions of West Street Limited | Wholesale & retail | 2020 |
| Occupational Health 1ST Limited | Real estate | 2011 |
| Ocean 2 Realisations Limited | Wholesale & retail | 1996 |
| Ocean Compass Group Ltd | Transport & logistics | 2021 |
| Ocean Edge Public Relations and Marketing Ltd | Professional & scientific | 2011 |
| Ocean Edge Resource Management Ltd. | Professional & scientific | 2000 |
| Ocean Fish and Kebab Limited | Hospitality | 2023 |
| Ocean Flexible Coatings Ltd | Wholesale & retail | 2022 |
| Ocean Gate Transfers Ltd | Transport & logistics | 2025 |
| Ocean Infinity Group (UK) Ltd | Professional & scientific | 1995 |
| Ocean Infinity Innovations Limited | Information & communication | 2021 |
| Ocean International Freight Services Limited | Transport & logistics | 1989 |
| Ocean Oncology Ltd | Health & social care | 2019 |
| Ocean Quay DRY Dock Limited | Real estate | 2024 |
| Ocean Quay Group Limited | Real estate | 2010 |
| Ocean Quay Investments Limited | Real estate | 2011 |
| Ocean Quay Marina Limited | Real estate | 2000 |
| Ocean Quay Property Company Limited | Financial services | 2011 |
| Ocean Safety Limited | Manufacturing | 1993 |
| Ocean Saviour Limited | Water & waste | 2018 |
| Ocean Sprayz Ltd | Wholesale & retail | 2024 |
| Ocean Venture Yacht Sales and Services Limited | Wholesale & retail | 2024 |
| Ocean Village Hospitality Limited | Hospitality | 2021 |
| Ocean Village Marina (Apartment) Management Company NO. 1 Limited | Households | 1987 |
| Ocean Village Marina (Apartment) Management Company NO. 2 Limited | Households | 1987 |
| Ocean Village Marina (Apartment) Management Company NO. 3 Limited | Real estate | 1987 |
| Ocean Village Marina (Apartment) Management Company NO. 4 Limited | Households | 1987 |
| Ocean Village Marina (Apartment) Management Company NO.6 Limited | Professional & scientific | 1988 |
| Ocean Village Marina (Apartment) Management Company NO.7 Limited | Professional & scientific | 1988 |
| Ocean Village Marina Management Company Limited | Real estate | 1987 |
| Ocean Village Marina Residents Association Limited | Other services | 2021 |
| Ocean Village Resorts Limited | Administrative & support | 2004 |
| Ocean Youth Trust South | Arts & recreation | 1999 |
| Oceanair Express (UK) Ltd | Transport & logistics | 2013 |
| Oceanair Express Logistics Limited | Transport & logistics | 2008 |
| Oceanair Handling Services Ltd | Transport & logistics | 2021 |
| Oceanair In-Flight Supplies Ltd | Transport & logistics | 2021 |
| Oceanic (Gosport) Limited | Real estate | 2015 |
| Oceanic (Woolston) Limited | Real estate | 2015 |
| Oceanic Estates SPV Ltd | Financial services | 2021 |
| Oceanic Finance Limited | Financial services | 2014 |
| Oceanic Galaxy Limited | Real estate | 2019 |
| Oceanmaster Limited | Extraterritorial | 2006 |
| Oceanologic Ltd | Extraterritorial | 2017 |
| Oceanpetal Supermarket Ltd | Wholesale & retail | 2025 |
| Oceanqs Cost Management Ltd | Professional & scientific | 2026 |
| Oceans Armour Co Limited | Manufacturing | 2025 |
| Oceans Reach (Cornwall) Ltd. | Real estate | 2014 |
| Oceantech UK Ltd | Construction | 2007 |
| Oceanteriors Limited | Professional & scientific | 2019 |
| Oceanview Investments Limited | Real estate | 2015 |
| OCG Properties Ltd | Households | 2013 |
| OCO Consult Ltd | Professional & scientific | 2018 |
| Ocram IT Ltd | Wholesale & retail | 2011 |
| Octagon Dental Centre Limited | Health & social care | 2010 |
| Octagon Southern Ltd | Wholesale & retail | 2020 |
| Octangle Ltd | Professional & scientific | 2018 |
| Octatransport Ltd | Transport & logistics | 2024 |
| Octave Accountants Limited | Professional & scientific | 2015 |
| Octic Ltd | Wholesale & retail | 2025 |
| October Some When Limited | Information & communication | 2020 |
| Octommerce Ltd | Information & communication | 2025 |
| Octonite Ltd | Information & communication | 2024 |
| Octopi Software Ltd | Administrative & support | 2017 |
| Octopush X Ltd | Information & communication | 2026 |
| OD Electrical Contracting Ltd | Construction | 2012 |
| OD Socials Ltd | Information & communication | 2025 |
| Odds + Ends Creative Ltd | Professional & scientific | 2024 |
| Odena Limited | Financial services | 2020 |
| Odeys Investment Limited | Information & communication | 2017 |
| Odgconsulting Limited | Public administration | 2022 |
| Odoi Logistics Limited | Wholesale & retail | 2025 |
| Odontoblast Limited | Health & social care | 2023 |
| Odour Control Ltd | Water & waste | 2007 |
| Odyssey Phase 2 Management Limited | Households | 2023 |
| Odyssey Training Limited | Professional & scientific | 1997 |
| OEC Electrical Systems Ltd | Construction | 2026 |
| OEM (North) Limited | Professional & scientific | 2017 |
| OEM Solutions Ltd | Information & communication | 2020 |
| Oema Chem Limited | Manufacturing | 2010 |
| Oema Limited | Financial services | 2026 |
| OFF Grid Rentals Ltd | Real estate | 2024 |
| OFF the Gridd Limited | Wholesale & retail | 2023 |
| Offgrid Pro Limited | Wholesale & retail | 2022 |
| Offgryd Ltd | Administrative & support | 2026 |
| Offham/Rodmell Court Residents Company Limited | Households | 1986 |
| Office Assistance Direct Limited | Administrative & support | 2017 |
| Office Furniture and Interiors Limited | Wholesale & retail | 2007 |
| Office Graphics & Window Films Limited | Professional & scientific | 2023 |
| Office KIT (Solutions) Limited | Wholesale & retail | 2012 |
| Office Worker Ltd | Professional & scientific | 2019 |
| Officers Gardens Management Co. Ltd | Households | 2020 |
| Official Beauty CEO Ltd | Other services | 2026 |
| Officialpgi Ltd | Manufacturing | 2022 |
| Offix Limited | Transport & logistics | 2003 |