| Nylaser Limited | Administrative & support | 2007 |
| NYS Vehicle Hire & Sales Ltd | Wholesale & retail | 2023 |
| NZN Retail Ltd | Wholesale & retail | 2024 |
| NZP Care Limited | Real estate | 2025 |
| NZT Studios Limited | Wholesale & retail | 2025 |
| O & a Property Consultants Limited | Real estate | 2019 |
| O & B Liverpool Ltd | Hospitality | 2025 |
| O & G Medicolegal Limited | Health & social care | 2010 |
| O & J Estates Limited | Real estate | 2024 |
| O & S Homes Ltd | Construction | 2023 |
| O & T Transport & Haulage Ltd | Other services | 2014 |
| O a M Food Ltd | Hospitality | 2023 |
| O B Design and Build Ltd | Construction | 2017 |
| O C Retail Limited | Wholesale & retail | 2016 |
| O M Telecommunications Limited | Construction | 2018 |
| O N G Business Advisory Limited | Professional & scientific | 2024 |
| O Shaped Lawyer Limited | Professional & scientific | 2020 |
| O&C Interiors Ltd | Construction | 2022 |
| O&E Limited | Construction | 2026 |
| O&H Vehicle Conversions Limited | Manufacturing | 1988 |
| O&Hs Marine Ltd | Manufacturing | 2011 |
| O&L Developments Ltd | Real estate | 2024 |
| O&M International Limited | Information & communication | 2025 |
| O&V Investments Limited | Real estate | 2026 |
| O'Brien Accountants Ltd | Professional & scientific | 2018 |
| O'Brien T Limited | Wholesale & retail | 2023 |
| O'Brien Waterproofing Limited | Wholesale & retail | 2006 |
| O'Briens Plant Hire & Construction Ltd | Administrative & support | 2017 |
| O'Connell Property Management Ltd | Real estate | 2021 |
| O'Connell Site Services Limited | Construction | 1988 |
| O'Conner Investment LLP | | 2012 |
| O'Conner Properties Limited | Real estate | 2021 |
| O'Connors Legal Services Limited | Professional & scientific | 2018 |
| O'Connors LLP | | 2003 |
| O'Donnell Contractors Ltd | Construction | 2015 |
| O'Donnell Groundworks Ltd | Construction | 2012 |
| O'Grady Trading Limited | Professional & scientific | 2019 |
| O'Hara O'Hara Limited | Extraterritorial | 2015 |
| O'Loughlin & Co Ltd | Professional & scientific | 2014 |
| O'Neill & Rimmer Property Ltd | Real estate | 2019 |
| O'Neill Automotive Ltd | Manufacturing | 2016 |
| O'Neill Fine Wines Limited | Wholesale & retail | 1985 |
| O'Neill Medicalia Limited | Professional & scientific | 1984 |
| O'Neill Trade & Distribution Ltd | Wholesale & retail | 2024 |
| O'Neill-Jones Hair and Beauty Ltd | Other services | 2024 |
| O'Sullivan Holdings Ltd | Financial services | 2025 |
| O'Toole Property Holding Company Limited | Real estate | 2024 |
| O-Innovations Limited | Manufacturing | 2019 |
| O-Matcha Liverpool Limited | Hospitality | 2020 |
| O.A.H 2 Ltd | Wholesale & retail | 2021 |
| O.A.M Ventilation Services Limited | Construction | 2019 |
| O.D.A. Supplies Limited | Wholesale & retail | 1992 |
| O.L.M Properties Ltd | Real estate | 2020 |
| O.S.S. Fire & Security Ltd | Professional & scientific | 2007 |
| O.S.S. Security Limited | Professional & scientific | 1998 |
| O.V.A.S (NW) Ltd | Administrative & support | 2019 |
| O2O Engineering Limited | Professional & scientific | 2010 |
| O31 Limited | Hospitality | 2018 |
| Oak & Atlas Ltd | Wholesale & retail | 2018 |
| Oak & Stone Builders Ltd | Construction | 2023 |
| Oak Hill Operations Ltd | Administrative & support | 2026 |
| Oak Hill Park Holdings Limited | Real estate | 2025 |
| Oak House Residents Association Limited | Households | 2005 |
| Oak Shield Security Solutions Ltd | Administrative & support | 2019 |
| Oak Specialist Joinery Limited | Manufacturing | 2008 |
| Oak Tree Developments North West Limited | Hospitality | 2015 |
| Oakbay Services Limited | Manufacturing | 2001 |
| Oakbay Windows Ltd | Construction | 2011 |
| Oakbridge Advisory Group Limited | Professional & scientific | 2026 |
| Oakbrook Investments Limited | Financial services | 2026 |
| Oakbrook Property Services Limited | Real estate | 2026 |
| Oakclass Limited | Construction | 1978 |
| Oakcrest Developments (NW) Limited | Construction | 2017 |
| Oakcroft Homes Limited | Construction | 2017 |
| Oakdale Mersey Flat C.I.C. | Manufacturing | 2022 |
| Oakes Holdings Ltd | Real estate | 2017 |
| Oakfield Capital Finance Ltd | Construction | 2019 |
| Oakfield Grange (Liverpool) Management Company Limited | Households | 1994 |
| Oakfield House Limited | Households | 1995 |
| Oakfield Road Ltd | Hospitality | 2016 |
| Oakfield Roofing Services Ltd | Construction | 2025 |
| Oakham Management and Support Ltd | Health & social care | 2025 |
| Oakhouse Coffee Ltd | Hospitality | 2025 |
| Oakland CMS Ltd | Construction | 2015 |
| Oaklands Progression Trading Limited | Professional & scientific | 2016 |
| Oakleigh Court Management Company Limited | Households | 1998 |
| Oakleigh House Management Company Limited | Households | 2003 |
| Oakley Group Holdings Limited | Extraterritorial | 2014 |
| Oakley Transport Ltd | Transport & logistics | 2024 |
| Oakman Coaching Ltd | Other services | 2023 |
| Oakmere Clinical Services Ltd | Education | 2024 |
| Oakmere Construction and Maintenance Ltd | Construction | 2026 |
| Oakmere Estates (Liverpool) Limited | Real estate | 2016 |
| Oakmont Arborist & Ground Works Ltd | Wholesale & retail | 2018 |
| Oakmont Electrical Ltd | Construction | 2023 |
| Oakmore Investments Limited | Financial services | 2016 |
| Oakpark North West Limited | Real estate | 2025 |
| Oakridge Garden Design Limited | Administrative & support | 2025 |
| Oaks Property Ltd | Real estate | 2025 |
| Oakwalk Engineering Limited | Wholesale & retail | 2020 |