| Omega International Unit 2 Trading Limited | Extraterritorial | 2020 |
| Omega International Unit 3 Trading Limited | Extraterritorial | 2020 |
| Omega International Unit 4 Trading Limited | Other services | 2021 |
| Omega International Unit 5 Trading Limited | Extraterritorial | 2021 |
| Omega International Unit 6 Trading Limited | Extraterritorial | 2021 |
| Omega Therapies Holistic Centre and Training School Ltd | Health & social care | 2018 |
| Omnia Systems (UK) Limited | Information & communication | 2011 |
| ON Board Gaming Ltd | Wholesale & retail | 2024 |
| ON the Munchies Desserts Ltd | Hospitality | 2025 |
| ON the Munchies Ltd | Hospitality | 2020 |
| On.Ai Media Ltd | Professional & scientific | 2023 |
| Onan Limited | Wholesale & retail | 2020 |
| Once Upon a Time Party Planners Ltd | Arts & recreation | 2026 |
| One Eleven Capital Limited | Real estate | 2025 |
| One Fernhill Limited | Wholesale & retail | 2021 |
| One Health Film Limited | Information & communication | 2019 |
| One Solution Partners Group Ltd | Construction | 2026 |
| One Stop Recovery Services Ltd | Wholesale & retail | 2026 |
| Oneway Bikes Ltd | Wholesale & retail | 2024 |
| Online and Totally Fabulous Ltd | Professional & scientific | 2015 |
| Only One Planet Ltd | Arts & recreation | 2021 |
| Onqu Holdings Limited | Financial services | 2017 |
| Onqu Support Limited | Information & communication | 2020 |
| Ontrax Ltd | Administrative & support | 2008 |
| Onyx Healthcare Services Ltd | Health & social care | 2024 |
| Onyx Talent Asset Management Limited | Professional & scientific | 2020 |
| Onyxx Contracting Ltd | Construction | 2024 |
| Opal Home Improvements Ltd | Construction | 2021 |
| OPAL34 Ltd | Real estate | 2023 |
| Open Cinematic Ltd | Information & communication | 2019 |
| Openglobal E-Commerce Ltd | Information & communication | 2013 |
| Operation Hustle Ltd | Information & communication | 2024 |
| Ophelia-Mabelgolf Ltd | Wholesale & retail | 2026 |
| Ophret Group Limited | Manufacturing | 2019 |
| Opifex Software Solutions Limited | Information & communication | 2026 |
| Opine Trading Limited | Wholesale & retail | 2022 |
| OPK Consultants Ltd | Other services | 2024 |
| Opra Packaging Limited | Wholesale & retail | 1989 |
| Optima Window Cleaning Ltd | Administrative & support | 2025 |
| Optimal Manufacturing Holding Limited | Real estate | 2026 |
| Optimal Manufacturing Ltd | Manufacturing | 2022 |
| Optosolve LLP | | 2012 |
| Optosolve Research & Development Limited | Professional & scientific | 2014 |
| Oquinox Ltd | Information & communication | 1999 |
| Oranje Consulting Ltd | Professional & scientific | 2023 |
| Orchard Clothing Limited | Wholesale & retail | 2011 |
| Orchard Fulfilment Ltd | Manufacturing | 2020 |
| Orfaniotis Face Group Ltd | Health & social care | 2026 |
| Organicoath Ltd | Wholesale & retail | 2025 |
| Original Perios Ltd | Hospitality | 2023 |
| Original Simple Apparel Aesthetics Limited | Wholesale & retail | 2026 |
| Orion Business Support Ltd | Professional & scientific | 2020 |
| Orion Developments (Midlands) Limited | Construction | 2004 |
| Orion Supplies Ltd | Wholesale & retail | 2020 |
| Oriya Holistics Limited | Wholesale & retail | 2025 |
| Ormishers Limited | Administrative & support | 2004 |
| Ortus Group Professions Ltd | Professional & scientific | 2024 |
| Ortus Legal M&A Ltd | Professional & scientific | 2017 |
| Oscar Jacobs Ltd | Wholesale & retail | 2013 |
| Oscar Jacobs Vehicle Manager Ltd | Extraterritorial | 2017 |
| Oscott House Limited | Real estate | 2021 |
| Oscott Rowan Limited | Administrative & support | 2026 |
| Oscroft & Sons Group Ltd | Professional & scientific | 2010 |
| OSS Electrical Ltd | Construction | 2025 |
| OSS Properties Limited | Real estate | 2026 |
| Oswald Springs Company Limited | Extraterritorial | 2026 |
| Otter Display Limited | Administrative & support | 2012 |
| OUR Rooms Ltd | Hospitality | 2023 |
| Outdoor Building Solutions Ltd | Construction | 2016 |
| Outhouse-Uk Limited | Administrative & support | 2012 |
| Outsourcintel International Ltd | Administrative & support | 2024 |
| Ouvert Yale Limited | Professional & scientific | 2002 |
| Oxford Storage Yards and Containers Limited | Transport & logistics | 2025 |
| Oxfordshire Accommodation Ltd | Hospitality | 2021 |
| Oxyflame Holdings Limited | Construction | 2020 |
| Oxyflame Ltd | Construction | 2014 |
| Oxytreat Ltd | Health & social care | 2023 |
| OYL Ltd | Administrative & support | 2022 |
| OZ Holdings Ltd | Real estate | 2019 |
| P & E Sports CIC | Education | 2017 |
| P & E Sports Gyms Ltd | Arts & recreation | 2026 |
| P & E Sports Lettings Ltd | Arts & recreation | 2019 |
| P & E Sports Redditch Limited | Education | 2018 |
| P & H Lift Trucks Limited | Wholesale & retail | 2004 |
| P & L Clothing Limited | Administrative & support | 2015 |
| P & W Lift Services Limited | Manufacturing | 2013 |
| P B Robinson Properties Ltd | Real estate | 2023 |
| P D Models LE Limited | Professional & scientific | 2016 |
| P H F Training Ltd | Administrative & support | 2005 |
| P Hunt Maintenance Limited | Professional & scientific | 2025 |
| P I Rentals Limited | Real estate | 2020 |
| P K S Carpentry Limited | Construction | 2011 |
| P&C Testing Ltd | Construction | 2025 |
| P&J Service Cleaning Ltd | Administrative & support | 2023 |
| P&M Electrical Contractors Ltd | Construction | 2023 |
| P&P Events Limited | Hospitality | 2024 |
| P.J.A. Electrics Limited | Construction | 1981 |
| P.R. Accounting Limited | Professional & scientific | 1991 |
| P3 Sustainable Solutions Ltd | Real estate | 2012 |
| Pablo Pubs & Bars Limited | Hospitality | 2023 |