| Orbital Brokers (UK) Limited | Professional & scientific | 2024 |
| Orbital Journey Ltd | Information & communication | 2021 |
| Orchard Close Limited | Professional & scientific | 2002 |
| Orchard Construction Yorkshire Limited | Construction | 2016 |
| Orchard Court (Gildersome) Management Limited | Households | 2001 |
| Orchard Friary Ltd | Hospitality | 2024 |
| Orchard Gate Management Company Limited | Households | 2003 |
| Orchard Group Investments Ltd | Real estate | 2025 |
| Orchard Homes Yorkshire Limited | Construction | 2026 |
| Orchard Lettings (UK) Ltd | Real estate | 2005 |
| Orchard Lodgings Limited | Real estate | 2025 |
| Orchard Sanctuary Limited | Health & social care | 2026 |
| Orchard Springs Limited | Real estate | 2019 |
| Orchard Square Development Limited | Real estate | 2020 |
| Orchestras Live | Arts & recreation | 2006 |
| Orchid Heights Properties Limited | Real estate | 2021 |
| Orchid House Healthcare Solutions LLP | | 2024 |
| Orclui CIC | Information & communication | 2024 |
| Orderflo Limited | Information & communication | 2023 |
| Orderkrlo Ltd | Wholesale & retail | 2024 |
| Ordinary Day Productions Ltd | Professional & scientific | 2023 |
| Ordo Property Ltd | Real estate | 2017 |
| Ordragon Ltd | Hospitality | 2017 |
| Oree Activite Limited | Hospitality | 1992 |
| Oreeva Ltd | Wholesale & retail | 2026 |
| Oregano Catering Ltd | Hospitality | 2019 |
| Orenza Retails Limited | Manufacturing | 2025 |
| Orevia Ltd | Wholesale & retail | 2026 |
| Organic Internet Ltd | Information & communication | 2006 |
| Organic Pet Ltd | Manufacturing | 2024 |
| Organic RF Ltd | Professional & scientific | 2024 |
| Organically YOU Ltd | Other services | 2018 |
| Organiq Music Limited | Arts & recreation | 2005 |
| Organisation for Conflict Resolution & Reconciliation Ltd | Education | 2022 |
| Organisation Panafricaine Pour LA Paix ET LA Resolution DES Conflits Limited | Professional & scientific | 2024 |
| Organised Spaces Limited | Administrative & support | 2024 |
| ORH Property Limited | Real estate | 2020 |
| Oriel Commodities Limited | Wholesale & retail | 2018 |
| Oriel Editorial House Ltd | Professional & scientific | 2020 |
| Orient Foods Wholesale Ltd | Wholesale & retail | 2025 |
| Orient Gold Limited | Extraterritorial | 1996 |
| Oriental Delight Leeds Limited | Hospitality | 2023 |
| Oriental Kitchen Leeds Ltd | Hospitality | 2025 |
| Oriental Trade Ltd | Wholesale & retail | 2015 |
| Origin Architectural Ltd | Wholesale & retail | 2015 |
| Origin Coaching Ltd | Health & social care | 2021 |
| Origin Logistics Venture UK Limited Partnership | | 2024 |
| Original Equipment Parts Limited | Wholesale & retail | 2002 |
| Original Fisheries Leeds Limited | Hospitality | 2019 |
| Original Kids Ltd | Manufacturing | 2019 |
| Origo Arts Limited | Arts & recreation | 2025 |
| Orinoco Bearings Ltd | Manufacturing | 2008 |
| Oriole Media Ltd | Information & communication | 2012 |
| Orion Holdings ( Europe ) Ltd | Real estate | 2020 |
| Orion Land Holdings Ltd | Financial services | 2026 |
| Orion Racing Limited | Wholesale & retail | 2021 |
| Orion Trustees Limited | Administrative & support | 2023 |
| Orionpulse Group Limited | Financial services | 2025 |
| Orionyx Ltd | Wholesale & retail | 2025 |
| Oris Capital Ltd | Real estate | 2024 |
| Orissa Iona Broadcast Services Ltd | Information & communication | 2025 |
| Orium Consulting Ltd | Information & communication | 2025 |
| Orivia Pharmaceuticals Ltd | Wholesale & retail | 2025 |
| Orkka Holdings Limited | Wholesale & retail | 2026 |
| Orkka Limited | Financial services | 2026 |
| Orlando CRO Holdings Limited | Financial services | 2026 |
| Orlean Steven Ltd | Health & social care | 2014 |
| Ormad Properties Ltd | Real estate | 2020 |
| Ormandy Development Group Limited | Construction | 2020 |
| Ormerod Sutton Architects Limited | Professional & scientific | 2004 |
| Ornella Services (UK) Ltd | Financial services | 2022 |
| Ornella's Estates Ltd | Real estate | 2022 |
| ORO Limited | Manufacturing | 1999 |
| Oroma Organics Limited | Wholesale & retail | 2023 |
| Orsecho Aspinall Limited | Real estate | 2019 |
| Orsett Hall Banqueting & Conference Centre Limited | Hospitality | 2008 |
| Orsimpex Limited | Transport & logistics | 2014 |
| Orso Bianco Limited | Hospitality | 2025 |
| Ortaecious Skin Ltd | Other services | 2026 |
| Orteeco Ltd | Wholesale & retail | 2025 |
| Ortho DEV UK Limited | Administrative & support | 2023 |
| ORTHO4BONE MD Ltd | Health & social care | 2025 |
| Orthoalex Ltd | Health & social care | 2025 |
| Orthodontic Avenue Limited | Health & social care | 2024 |
| Orthogis Ltd | Information & communication | 2018 |
| Ortons Bakery Limited | Manufacturing | 2002 |
| Ortons Bakery Wholesale Limited | Manufacturing | 2017 |
| Ortopeym Limited | Health & social care | 2020 |
| Orya Styles Ltd | Other services | 2024 |
| Oryx Security Solutions Limited | Administrative & support | 2015 |
| OSA (UK) Limited | Health & social care | 2012 |
| Osbourne Court Residents Association (Bramley) Limited | Professional & scientific | 1985 |
| Oscar's PAW Club Ltd | Other services | 2021 |
| Oscars Morley Limited | Administrative & support | 2014 |
| Osea Transport Limited | Transport & logistics | 2025 |
| Oseppa Ltd | Professional & scientific | 2024 |
| Oseti Limited | Information & communication | 2014 |
| Osfx Global Ltd | Other services | 2025 |
| Osiddiq Ltd | Professional & scientific | 2019 |
| Osiris Estates Limited | Real estate | 2019 |