| Oblige Care Services Ltd | Administrative & support | 2016 |
| Ocean Stores Ltd | Wholesale & retail | 2020 |
| Octaloop Information Technology Network Services Ltd | Information & communication | 2019 |
| Octopus Security Global Ltd | Administrative & support | 2023 |
| ODD Bleat Ltd | Information & communication | 2014 |
| OGS Floor Screeding Limited | Construction | 2011 |
| OH WOW Cleaning Ltd | Administrative & support | 2025 |
| OHM in the Community CIC | Arts & recreation | 2025 |
| OHM Sports & Fitness Limited | Arts & recreation | 2015 |
| Okal Limited | Information & communication | 2022 |
| Ola's Garden Ltd | Other services | 2022 |
| Olgardens Limited | Administrative & support | 2013 |
| Olgardens Services Ltd | Administrative & support | 2025 |
| Olianto Ltd | Wholesale & retail | 2018 |
| Olivantin Ltd | Hospitality | 2026 |
| Olivia Fine Food Ltd | Wholesale & retail | 2020 |
| Olomukoro Ltd | Wholesale & retail | 2025 |
| Olympus Fire Detection Ltd | Construction | 2015 |
| OM IT Solutions Limited | Information & communication | 2008 |
| OM Logistic Services Limited | Transport & logistics | 2026 |
| OM Property Management Services Ltd | Real estate | 2025 |
| Omar AI Solutions Ltd | Information & communication | 2025 |
| Omass Games Ltd | Manufacturing | 2026 |
| Omer Superstore Ltd | Wholesale & retail | 2024 |
| Omer Transports Ltd | Transport & logistics | 2025 |
| Omni Express Limited | Transport & logistics | 2026 |
| Omniva Ltd | Wholesale & retail | 2026 |
| Omor Enterprise Ltd | Wholesale & retail | 2015 |
| Omsvb Solutions Ltd | Wholesale & retail | 2020 |
| One 4 Services ENG Ltd | Information & communication | 2023 |
| One Call Grab and Tipper Hire Ltd | Transport & logistics | 2016 |
| One Click Handling Limited | Transport & logistics | 2024 |
| One Hundred Castle Ltd | Extraterritorial | 2025 |
| One Mentor Ltd | Financial services | 2026 |
| One Thousand & One Ventures Ltd | Hospitality | 2023 |
| Onesurance Ltd | Information & communication | 2022 |
| Online Xperience Ltd | Professional & scientific | 2015 |
| Onlinecore UK Ltd | Wholesale & retail | 2021 |
| Onnara Ltd | Health & social care | 2018 |
| Onyx Global Monuments UK Limited | Administrative & support | 2019 |
| Open Book Business Ltd | Professional & scientific | 2022 |
| Open Growth Properties Limited | Real estate | 2025 |
| Open the Talent Box Ltd | Administrative & support | 2023 |
| Openstream Technologies Ltd | Information & communication | 2025 |
| Optima Build & Electrical Ltd | Construction | 2024 |
| Optimum Builders Ltd | Construction | 2021 |
| Optimus BIZ Solutions Limited | Information & communication | 2020 |
| Options Greathire Limited | Financial services | 2019 |
| Opul Limited | Wholesale & retail | 2018 |
| Opulent Management Services Limited | Real estate | 2025 |
| Opulent Real Estates Limited | Real estate | 2024 |
| Orbit International Trade Ltd | Wholesale & retail | 2021 |
| Orbixon Ltd | Information & communication | 2025 |
| Order for ME Ltd | Other services | 2022 |
| Organic ALE Ltd | Wholesale & retail | 2026 |
| Organic and Fresh LLP | | 2009 |
| Organic Delivery Company Ltd | Manufacturing | 2016 |
| Orient General Trading Ltd | Wholesale & retail | 2018 |
| Orimel Ltd | Professional & scientific | 2024 |
| Ormoon Limited | Hospitality | 2025 |
| Osba Limited | Transport & logistics | 2025 |
| Osei Krom Cash & Carry Limited | Wholesale & retail | 2010 |
| Oshijay Ceylon Ltd | Administrative & support | 2019 |
| OSS Digital Consulting Limited | Information & communication | 2020 |
| OSS Well Limited | Wholesale & retail | 2025 |
| Outset Haulage Ltd | Transport & logistics | 2020 |
| Overlord Games Ltd | Wholesale & retail | 2024 |
| Ovgent Ltd | Construction | 2025 |
| Owen White & Catlin LLP | | 2009 |
| Oxford Global Leadership Centre Ltd | Professional & scientific | 2023 |
| OXO3 Ltd | Manufacturing | 2024 |
| Oxour Ltd | Wholesale & retail | 2020 |
| OYH Network Ltd | Transport & logistics | 2024 |
| P B 13 Gill Group Limited | Construction | 2023 |
| P Kapoor Investments Ltd | Real estate | 2020 |
| P Madaar Limited | Manufacturing | 2025 |
| P Naher Limited | Professional & scientific | 2019 |
| P Quinn Ceilings & Partitions Ltd | Construction | 2013 |
| P R Nicholls Plant Hire Ltd. | Construction | 2014 |
| P Young Transport Limited | Transport & logistics | 2003 |
| P&B Projects Ltd | Construction | 2025 |
| P&F Professional Services Ltd | Construction | 2016 |
| P&G Nexus Ltd | Wholesale & retail | 2024 |
| P&W Services Limited | Transport & logistics | 2015 |
| P.D.Compliance Limited | Financial services | 2015 |
| P.E. Design Ltd | Extraterritorial | 2020 |
| P.H. Thomas and Company Limited | Construction | 1996 |
| P.J.M.N Limited | Professional & scientific | 2019 |
| P2ESOLUTIONS Ltd | Construction | 2023 |
| Pabro Healthcare Ltd | Health & social care | 2023 |
| Pace Cargo UK Ltd | Transport & logistics | 2014 |
| Pace Construction Ltd | Construction | 2015 |
| Pacific Dragon Capital Limited | Real estate | 2010 |
| Pacorro Ltd | Information & communication | 2011 |
| Pakistan Welfare Association (Hounslow) Limited | Other services | 2022 |
| Palawan Protection Specialist Ltd | Financial services | 2023 |
| Palm Treees Ltd | Professional & scientific | 2022 |
| Panglobal Media Solutions Limited | Information & communication | 2023 |
| Par-Tech Solutions Ltd | Professional & scientific | 2013 |
| Paradice Desserts Limited | Hospitality | 2020 |