| Orca (Clifton) Limited | Real estate | 2016 |
| Orca Business Ltd | Energy | 2025 |
| Orca Electrical Ltd | Construction | 2019 |
| Orca Investments Holdings Limited | Financial services | 2017 |
| Orca Medical Limited | Wholesale & retail | 2017 |
| Orca Protection Ltd | Administrative & support | 2025 |
| Orca Renewables Limited | Construction | 2022 |
| Orchard (Bristol) Ltd | Other services | 2025 |
| Orchard Close (Congresbury) Management Limited | Other services | 1997 |
| Orchard Collective Companies Ltd | Wholesale & retail | 2022 |
| Orchard Cottages Downend Limited | Households | 2002 |
| Orchard Court Property Management (Filton) Company Limited | Households | 1984 |
| Orchard Draughting Limited | Professional & scientific | 2004 |
| Orchard Estate Administration Services Limited | Professional & scientific | 2019 |
| Orchard Executives Limited | Financial services | 2015 |
| Orchard Flexible Packaging Limited | Wholesale & retail | 1988 |
| Orchard Homes Design and Build Limited | Construction | 2015 |
| Orchard ITC Limited | Construction | 2015 |
| Orchard LEA Nursery Limited | Health & social care | 2008 |
| Orchard Leigh Camphill Community | Health & social care | 2013 |
| Orchard Livestock Supplies Ltd | Wholesale & retail | 2025 |
| Orchard Lodge (Management) Bath Limited | Households | 2003 |
| Orchard London Ltd | Wholesale & retail | 2025 |
| Orchard Mead (UK) Limited | Construction | 2009 |
| Orchard Meadows (Churchill) Management Company Limited | Households | 2026 |
| Orchard Meadows (Cleeve Prior) Management Company Limited | Households | 2026 |
| Orchard Mill Rangeworthy Management Company Limited | Households | 2026 |
| Orchard Properties Bristol Limited | Real estate | 2025 |
| Orchard Psychiatry Services Ltd | Health & social care | 2024 |
| Orchard Sales Ltd | Wholesale & retail | 2020 |
| Orchard SW Ltd | Construction | 2022 |
| Orchard Tax Services Limited | Professional & scientific | 2002 |
| Orchard Vale Kingswood Management Company Limited | Households | 2018 |
| Orchard Vale Management Limited | Households | 2015 |
| Orchard Willow Lodge | Professional & scientific | 2024 |
| Orchid Consultancy Services Ltd | Professional & scientific | 2021 |
| Orchid Management Limited | Hospitality | 2011 |
| Orchid S&N House Ltd | Real estate | 2024 |
| Orchid Video Limited | Wholesale & retail | 1990 |
| Ordered Management Ltd | Professional & scientific | 2005 |
| Ordered Management Secretary Ltd | Professional & scientific | 2005 |
| Ordway House Ltd | Hospitality | 2015 |
| ORE Scaffolding Ltd | Construction | 2024 |
| Oren Limited | Administrative & support | 2004 |
| Organel Limited | Professional & scientific | 2013 |
| Organic Blooms Ltd | Wholesale & retail | 2019 |
| Organic Network Ltd | Information & communication | 2024 |
| Organics Collective CIC | Information & communication | 2025 |
| Organisation Development Solutions Ltd | Administrative & support | 2007 |
| Organisation for Propaganda Studies | Professional & scientific | 2017 |
| Organizational Maturity Services LLP | | 2014 |
| Orgman Security Ltd | Administrative & support | 2024 |
| Orian Limited | Administrative & support | 1997 |
| Orican Ltd | Information & communication | 2017 |
| Orient Vision Limited | Arts & recreation | 1982 |
| Oriental City Management Ltd | Real estate | 2020 |
| Oriental Garden Swansea Ltd | Hospitality | 2026 |
| Oriental Homes Ltd | Real estate | 2025 |
| Oriental Market & Trading Ltd | Wholesale & retail | 2013 |
| Origami Dinosaur Creations Ltd | Information & communication | 2026 |
| Origami Events Limited | Administrative & support | 2009 |
| Origin 3 Ltd | Professional & scientific | 2007 |
| Origin Butchers Limited | Wholesale & retail | 2025 |
| Origin Capital Ltd | Professional & scientific | 2001 |
| Origin Capital Nominees Ltd | Extraterritorial | 2018 |
| Origin Capital Partners LLP | | 2023 |
| Origin OPS Limited | Professional & scientific | 2024 |
| Origin Series Athletic Ltd | Arts & recreation | 2019 |
| Origin Series Programming Ltd | Arts & recreation | 2018 |
| Origin Tattoo & AE Ltd | Other services | 2023 |
| Origin Workspace Ltd | Real estate | 2017 |
| Original Catapult Developments Limited | Professional & scientific | 2022 |
| Original Construction Company Limited | Real estate | 1996 |
| Original Design Therapeutic Technologies Ltd | Manufacturing | 2019 |
| Original Hot Spot Ltd | Hospitality | 2025 |
| Original Mango Group Ltd | Information & communication | 2020 |
| Original Marquetry Limited | Manufacturing | 2008 |
| Origo Property Solutions Ltd | Other services | 2017 |
| Orika Sports Ltd | Wholesale & retail | 2021 |
| Orion Consult Limited | Health & social care | 2023 |
| ORJ Recruitment Ltd | Administrative & support | 2026 |
| Orkin UK Services Limited | Administrative & support | 2023 |
| Orku Health Limited | Health & social care | 2021 |
| Orla Properties Bath Ltd | Real estate | 2026 |
| Orlamax Ltd | Health & social care | 2023 |
| Orleton Rise Park Limited | Hospitality | 1996 |
| Orley Kustoms Ltd | Wholesale & retail | 2014 |
| Orli Tech Ltd | Information & communication | 2023 |
| Orman Consultancy Limited | Professional & scientific | 2020 |
| Ormu Properties Ltd | Real estate | 2015 |
| Ornlick Limited | Health & social care | 2015 |
| ORO Cartagena Ltd | Real estate | 2026 |
| Orobosa Limited | Public administration | 2022 |
| Oromah Flex Ltd | Administrative & support | 2022 |
| Oromah International Ltd | Health & social care | 2019 |
| Oromah Investment Ltd | Real estate | 2023 |
| Oros Marius Ltd | Transport & logistics | 2019 |
| Orouji Corporation Ltd | Wholesale & retail | 2025 |
| Orsa Adventure Holdings Ltd | Financial services | 2025 |
| Orsa Adventures Ltd | Administrative & support | 2025 |