| Oakbrook Loans Limited | Professional & scientific | 2012 |
| Oakdale Detailing Ltd | Administrative & support | 2024 |
| Oakdale Manufacturing (UK) Limited | Manufacturing | 2007 |
| Oakdale Ozier Limited | Real estate | 2004 |
| Oakdene Automatic Transmissions Ltd | Wholesale & retail | 2023 |
| Oakeaston Limited | Real estate | 1960 |
| Oakenhall 1969 Limited | Extraterritorial | 2015 |
| Oakenhall Building Services Limited | Construction | 2006 |
| Oakfield Heritage Ltd | Professional & scientific | 2026 |
| Oakfield Labs Ltd | Information & communication | 2018 |
| Oakgrove Partners Ltd | Wholesale & retail | 2025 |
| Oakham Investments Limited | Construction | 1963 |
| Oakham Property Partners Limited | Real estate | 2025 |
| Oakland & SON Limited | Wholesale & retail | 2015 |
| Oaklands SEN School Berkshire Limited | Education | 2023 |
| Oakmere Holdings Group (UK) Ltd | Real estate | 2022 |
| Oakmere Property Holdings Ltd | Real estate | 2026 |
| Oakmont Roofing Services Ltd | Construction | 2025 |
| Oakmont Tax Limited | Professional & scientific | 2025 |
| Oakmoor (Sharmans Cross) Limited | Construction | 2006 |
| Oakmoor Estates (Holdings) Limited | Professional & scientific | 2012 |
| Oakmoor Estates Limited | Construction | 2001 |
| Oaknest Lettings Ltd | Real estate | 2025 |
| Oakridge Electrical Services Ltd | Construction | 2026 |
| Oakridge Global Limited | Professional & scientific | 2013 |
| Oakridge Landscapes Ltd | Administrative & support | 2025 |
| Oaks Pro Clean Ltd | Administrative & support | 2022 |
| Oaktree Garage (Nottm) Limited | Wholesale & retail | 2004 |
| Oaktree Leasing Ltd | Wholesale & retail | 2016 |
| Oaktree Lettings & Management Ltd | Real estate | 2011 |
| Oakville James Ltd | Professional & scientific | 2018 |
| Oakwell Living Limited | Real estate | 2025 |
| Oakwood (Bingham) Physiotherapy Limited | Health & social care | 2011 |
| Oakwood Archer Limited | Wholesale & retail | 2013 |
| Oakwood Betwright Limited | Arts & recreation | 2024 |
| Oakwood Bingham Estates Limited | Households | 2022 |
| Oakwood Homes (UK) Ltd | Construction | 2012 |
| Oakwood Investment Property Ltd | Real estate | 2024 |
| Oakwyn Joinery Limited | Construction | 2026 |
| Oarsport Limited | Wholesale & retail | 1990 |
| Oasis Business Consulting Limited | Education | 2024 |
| Oasis Commercials LLP | | 2022 |
| Oasis Consulting Limited | Professional & scientific | 2013 |
| OB Plant Ltd | Manufacturing | 2016 |
| OB PR Consultancy Limited | Professional & scientific | 2023 |
| OB Steel Frame Consultancy Ltd | Professional & scientific | 2019 |
| Ob's Barbers and Hairdressers Limited | Other services | 2025 |
| Obaya Limited | Real estate | 2024 |
| Obels Enterprises Ltd | Transport & logistics | 2023 |
| OBI Davis Ltd | Information & communication | 2023 |
| OBI Haulage Limited | Transport & logistics | 2016 |
| Objectdb Software Ltd | Information & communication | 2010 |
| Objective Sheep Ltd | Information & communication | 2012 |
| Oblu Investments Limited | Real estate | 2016 |
| Obotrans Ltd | Transport & logistics | 2019 |
| Obscure OWL Ltd | Information & communication | 2026 |
| Obsidara Studio Ltd | Administrative & support | 2025 |
| Obsidian Motor Sales Ltd | Wholesale & retail | 2026 |
| Obsidian Trent Ltd | Real estate | 2023 |
| Obsido Capitis Ltd | Information & communication | 2021 |
| Obstacles to Empowerment Ltd | Education | 2025 |
| Obtech Soln Ltd | Professional & scientific | 2025 |
| OBU Ltd | Professional & scientific | 2018 |
| Obvious Things Ltd | Information & communication | 2015 |
| OC Nottingham Ltd | Hospitality | 2019 |
| Occutherapy Ltd | Health & social care | 2025 |
| OCD Rigging Limited | Information & communication | 2012 |
| Ocean Associates Limited | Professional & scientific | 2002 |
| Ocean Breeze Residential Care Home Limited | Health & social care | 2010 |
| Ocean Decorators Ltd | Construction | 2022 |
| Ocean Fish Bar Pelsall Limited | Hospitality | 2024 |
| Ocean Holdings Limited | Financial services | 2024 |
| Ocean Investments & Holdings Limited | Real estate | 2019 |
| Ocean Maintenance-Uk Limited | Construction | 2020 |
| Ocean Marketing Ltd | Professional & scientific | 2024 |
| Ocean of Angels Ltd | Real estate | 2019 |
| Ocean Palms Limited | Hospitality | 2024 |
| Ocean Property Limited | Construction | 2019 |
| Ocean Success Ltd | Hospitality | 2013 |
| Ocean Walker Limited | Education | 2017 |
| Oceanfresh@Steves Limited | Hospitality | 2024 |
| Oceanova Services Limited | Financial services | 2016 |
| Oceans of Notions Limited | Manufacturing | 1939 |
| Oceans Partyhouse Limited | Arts & recreation | 2011 |
| Oceanum Caruleum Ltd | Wholesale & retail | 2023 |
| Oceanwest Property Management Limited | Real estate | 2023 |
| Oceanwizard Ltd | Information & communication | 2017 |
| Ocie Nottingham Ltd | Professional & scientific | 2026 |
| Ockerby Stores Ltd | Wholesale & retail | 2024 |
| OCM Property Limited | Real estate | 2020 |
| OCR Estate Limited | Real estate | 2020 |
| OCS Consultancy Services Limited | Professional & scientific | 2013 |
| OCS Development Projects Limited | Construction | 2018 |
| OCS Financial Planning Ltd | Professional & scientific | 2017 |
| OCT Brickwork and Construction Ltd | Construction | 2023 |
| Octago.Co.Uk Limited | Administrative & support | 2025 |
| Octavia Designs Limited | Manufacturing | 2026 |
| Octavian Builders Express Ltd | Construction | 2022 |
| Octavian Facilities Management Limited | Administrative & support | 2016 |
| Octavian IT Limited | Information & communication | 2016 |