| Opulentus Holdings Ltd | Real estate | 2022 |
| OQL USA Ltd | Arts & recreation | 2022 |
| Orbit Care Ltd | Health & social care | 2021 |
| Orbital Consultancy Limited | Professional & scientific | 2003 |
| Orbital Repair Solutions (Central) Ltd | Wholesale & retail | 2023 |
| Orbital Repair Solutions Ltd | Wholesale & retail | 2010 |
| Orchard Grove (Upper Grosvenor Road) Management Limited | Households | 1979 |
| Orchard Mews Consulting Limited | Professional & scientific | 2011 |
| Orchard Post Limited | Information & communication | 2008 |
| Ordination Candidate's Training Fund Incorporated Trust Limited(The) | Professional & scientific | 1937 |
| Organic Blend Ltd | Hospitality | 2026 |
| Organika Limited | Information & communication | 2008 |
| Origin Sports Group Limited | Arts & recreation | 2015 |
| Original Drinkup Ltd | Wholesale & retail | 2021 |
| Ormsby Consulting Limited | Professional & scientific | 2025 |
| Ornate Kitchens & Interiors Limited | Construction | 2022 |
| Orrisr Limited | Extraterritorial | 2024 |
| Orvelo Ltd | Professional & scientific | 2021 |
| Orville Consulting Limited | Professional & scientific | 2013 |
| Orygamy Group UK Ltd | Wholesale & retail | 2025 |
| Osbl Properties Limited | Real estate | 2025 |
| Oscar Sterling Solutions Ltd | Professional & scientific | 2024 |
| Ospin Design & Build Ltd | Construction | 2025 |
| Ospringe Place Residents Association Ltd | Households | 2016 |
| OSTARA203 Ltd | Professional & scientific | 2019 |
| Osteo Rehab Limited | Health & social care | 2014 |
| Otter Media Limited | Professional & scientific | 2025 |
| OUR House in Sunny Tunny Limited | Households | 2002 |
| Ourgaffs Investment Limited | Real estate | 2013 |
| Ourgaffs LLP | | 2013 |
| Outer Dimension Dives Ltd. | Wholesale & retail | 2023 |
| Outside the Box Creations Ltd | Professional & scientific | 2023 |
| Outsource Digital Media Limited | Information & communication | 2005 |
| Outward Limited | Construction | 1983 |
| Ovasite Ltd | Professional & scientific | 2024 |
| Overland 4X4 Adventures Ltd | Hospitality | 2023 |
| Owen Court Management Company Limited | Households | 2014 |
| Owilliams Ltd | Wholesale & retail | 2025 |
| Owlcroft UK Limited | Professional & scientific | 2014 |
| Ownership Works Limited | Professional & scientific | 2023 |
| Owqa Ltd | Information & communication | 2024 |
| Oxbridge Solicitors Ltd | Professional & scientific | 2024 |
| OXG Consulting Limited | Professional & scientific | 2023 |
| Oyster Interiors Limited | Real estate | 2020 |
| Oyster Worldwide Limited | Administrative & support | 2006 |
| Ozgem Limited | Other services | 2009 |
| Ozgul Ltd | Other services | 2011 |
| Ozgurmedia Limited | Hospitality | 2021 |
| Ozzle Limited | Administrative & support | 2003 |
| O’Briens Electrical Services Ltd | Administrative & support | 2016 |
| P & a Sharville Limited | Administrative & support | 2003 |
| P & a Software Services Limited | Information & communication | 2024 |
| P & K Anderson LLP | | 2012 |
| P & L Investments (TW) Limited | Real estate | 2026 |
| P & M Flowers Limited | Wholesale & retail | 2011 |
| P Harris Engineering Limited | Information & communication | 2003 |
| P Little Groundworks Limited | Construction | 2014 |
| P&B Business Solutions Ltd | Financial services | 2024 |
| P. & H. Harrison Limited | Real estate | 1976 |
| P.H.D. Properties Limited | Real estate | 1972 |
| P.J. Mercer Agencies Limited | Other services | 2009 |
| P4DZ Limited | Professional & scientific | 2025 |
| PA Gooch Design Ltd | Professional & scientific | 2025 |
| Paam Courriers Ltd | Transport & logistics | 2021 |
| Paari Ltd | Information & communication | 2026 |
| Paari Trading Ltd | Wholesale & retail | 2026 |
| Pablo Films Limited | Information & communication | 2008 |
| Pabspies Ltd | Wholesale & retail | 2026 |
| Pabtech Limited | Information & communication | 2022 |
| Pace Insights Limited | Professional & scientific | 2008 |
| Pacemanor Limited | Real estate | 1981 |
| Pacifico Holdings Ltd | Other services | 2013 |
| Pacifico Medical Limited | Health & social care | 2024 |
| Packyourbags Limited | Professional & scientific | 1999 |
| Packyourbags.Com Limited | Professional & scientific | 2000 |
| Paddock View Frant Management Co Ltd | Households | 2021 |
| Paffé Ltd | Wholesale & retail | 2023 |
| Pain and Nociception Group Ltd | Health & social care | 2023 |
| Painted House Kent Limited | Wholesale & retail | 2019 |
| Paintngo Ltd | Arts & recreation | 2025 |
| Paintr Group Limited | Construction | 2025 |
| Palafox Ltd | Information & communication | 2026 |
| Palazzetti Original Styles Limited | Construction | 2011 |
| Paley DAB Limited | Real estate | 2025 |
| Paley Farm Limited | Agriculture & fishing | 2016 |
| Paley Farm Shop Ltd | Wholesale & retail | 2021 |
| Paley MGB Limited | Real estate | 2025 |
| Palfi Ltd | Information & communication | 2014 |
| Palimpscape Limited | Professional & scientific | 2019 |
| Palladio London Ltd | Construction | 2020 |
| Pallas Investments LLP | | 2025 |
| Pallet Media Limited | Manufacturing | 2023 |
| Palm Productions Limited | Professional & scientific | 2006 |
| Palmer & Partners Limited | Real estate | 1974 |
| Palms and Evergreens Ltd | Agriculture & fishing | 2026 |
| Pamodzi Limited | Professional & scientific | 2014 |
| Pamplemousse London Limited | Health & social care | 2022 |
| Pampos Advisory Limited | Professional & scientific | 2025 |
| PAN Post Ventures Limited | Real estate | 2026 |
| Pandapaw Limited | Hospitality | 2024 |