| Occasions by Noor Ltd | Wholesale & retail | 2023 |
| Octomation Limited | Information & communication | 2021 |
| Oddball Designs Limited | Wholesale & retail | 2019 |
| Odyssey Commercial Properties Limited | Real estate | 2007 |
| OES Recruitment Limited | Administrative & support | 2022 |
| Office Interiors Wholesale Limited | Wholesale & retail | 1983 |
| Ogden Fibres Limited | Manufacturing | 1921 |
| Ogden Fulfilment Limited | Transport & logistics | 2013 |
| OGL (Construction & Developments) Ltd | Construction | 2019 |
| OGL Construction Ltd | Extraterritorial | 2023 |
| OGL Real Estate Ltd | Real estate | 2019 |
| Oil-Line Heating Services Limited | Construction | 2013 |
| OJB Joinery Ltd | Construction | 2018 |
| Old Guard JIU Jitsu Limited | Arts & recreation | 2024 |
| Old Time Fisheries Limited | Hospitality | 2026 |
| Olicana Consulting Services Limited | Professional & scientific | 2024 |
| Olive & Green Limited | Wholesale & retail | 2025 |
| Olive Care Agency Ltd | Health & social care | 2019 |
| Olive Lounge Travel (Bingley) Ltd | Real estate | 2023 |
| Olive Lounge Travel at Home Limited | Administrative & support | 2025 |
| Olive Lounge Travel Holdings Ltd | Financial services | 2026 |
| Olive Lounge Travel Ilkley Limited | Administrative & support | 2026 |
| Olive Lounge Travel Limited | Administrative & support | 2015 |
| Olive Pharma Limited | Health & social care | 2013 |
| Oliver's Barbers Limited | Other services | 2011 |
| Oliyamart Ltd | Wholesale & retail | 2025 |
| Olpa Group Limited | Information & communication | 2024 |
| OLV Global Limited | Professional & scientific | 2023 |
| Omega Solutions Cross Hills Limited | Professional & scientific | 2021 |
| Omega Windows UK Ltd | Manufacturing | 2023 |
| Omni Metals Ltd | Wholesale & retail | 2025 |
| Omnia Platforms Ltd | Information & communication | 2026 |
| Omnific Design Ltd | Professional & scientific | 2022 |
| Omniq Ltd | Financial services | 2026 |
| OMS Technologies UK Ltd | Information & communication | 2026 |
| ON the Go Wash Detailing Ltd | Wholesale & retail | 2025 |
| Onassist Ltd | Health & social care | 2023 |
| One Contact Property Solutions Limited | Construction | 2015 |
| One Estates Yorkshire Ltd | Real estate | 2021 |
| One Financial Group Ltd | Financial services | 2021 |
| One Stop Phone Mart Ltd | Wholesale & retail | 2023 |
| One TEN Advisors Ltd | Other services | 2022 |
| One-Off Developments (Dalston) Ltd | Construction | 2016 |
| Onedafull Limited | Wholesale & retail | 2024 |
| Onedate App Limited | Information & communication | 2025 |
| Onewood Developments Limited | Real estate | 2016 |
| Onnit Bikes Limited | Wholesale & retail | 2015 |
| Onsupport Ltd | Health & social care | 2023 |
| Onyx Technology Limited | Wholesale & retail | 2026 |
| Opal Elevators Limited | Manufacturing | 2004 |
| Opal Lifts Limited | Manufacturing | 2020 |
| Open Pharma Technologies Ltd | Information & communication | 2026 |
| Openskies Brand Management Consultancy Limited | Professional & scientific | 2003 |
| Operational Consultancy Cowling Limited | Professional & scientific | 2020 |
| Oprisan Trans Limited | Transport & logistics | 2025 |
| Optimistic Business Tips Limited | Professional & scientific | 2014 |
| Optimum Fireworks Limited | Arts & recreation | 2017 |
| Opusdatum Ltd | Professional & scientific | 2007 |
| OR3O Construction Limited | Construction | 2026 |
| Orbital 24 Limited | Administrative & support | 2001 |
| Orbixia Ltd | Wholesale & retail | 2025 |
| Orbuno Ltd | Wholesale & retail | 2025 |
| ORIGIN8 Haworth Ltd | Wholesale & retail | 2017 |
| Original Mini ME Ltd | Manufacturing | 2023 |
| Orion Events Ltd | Administrative & support | 2026 |
| Orion Metal Doors Ltd | Construction | 2025 |
| Orla Destinations Limited | Real estate | 2026 |
| Orthotic Medical Engineering Limited | Manufacturing | 2014 |
| OUD UL Zahra Ltd | Wholesale & retail | 2025 |
| Oughtibridge Limited | Information & communication | 1994 |
| OUR Kitchen Shop Ltd | Wholesale & retail | 2024 |
| Ouse Tendering Services Ltd | Information & communication | 2024 |
| Outside UK Limited | Professional & scientific | 2004 |
| Outsourced Back Office Limited | Administrative & support | 2020 |
| Over Board Packaging Ltd | Manufacturing | 2024 |
| OWL Holiday Cottages Limited | Hospitality | 2018 |
| Owthwaite Hospitality Consulting Ltd | Professional & scientific | 2026 |
| Ox'Nop Coffee Shop Ltd | Hospitality | 2026 |
| Oxenhope Chambers Limited | Health & social care | 2014 |
| Oxenhope Limited | Construction | 2017 |
| Oxenhope Properties LLP | | 2012 |
| Oxenhope SPV 1 Limited | Construction | 2026 |
| Oxford Private Hire Ltd | Transport & logistics | 2012 |
| Oxford Tyre & Battery Ltd. | Wholesale & retail | 2007 |
| Oxford Tyres Limited | Wholesale & retail | 2019 |
| P & a Eastburn Limited | Financial services | 2025 |
| P & B Kennedy Holdings Limited | Health & social care | 1995 |
| P & H Consultancy Services Limited | Professional & scientific | 2018 |
| P and P Gill Limited | Wholesale & retail | 2007 |
| P Johnson Plumbing & Heating Limited | Construction | 2025 |
| P O'Mahoney (Groundworks) Limited | Construction | 2006 |
| P S G R Limited | Construction | 2019 |
| P T Courier Services (UK) Limited | Transport & logistics | 2013 |
| P&M Properties (Yorkshire) Limited | Financial services | 2023 |
| P. Hindle 'Inspirations' Limited | Administrative & support | 2003 |
| P.A Power Ltd | Wholesale & retail | 2019 |
| P.H.V. Systems Limited | Construction | 1995 |
| P.O.S. Print Limited | Real estate | 1993 |
| P4 Solar Ltd | Construction | 2022 |
| P4 Technologies Group Ltd | Professional & scientific | 2015 |