| Orchard Grove Developments Limited | Construction | 1997 |
| Orchard Marina & Boat Builders Limited | Manufacturing | 2003 |
| Orchard Marina Limited | Manufacturing | 2015 |
| Orchard Rigg Trading Limited | Professional & scientific | 2017 |
| Orchard Secured Capital Limited | Financial services | 2014 |
| Orchardhall Ltd | Real estate | 2012 |
| Orchid Care Northwest Ltd | Health & social care | 2024 |
| Orchid Enterprises (North West) Ltd | Financial services | 2017 |
| Orchid Property 2 Limited | Real estate | 2008 |
| Orchid Property Group Limited | Real estate | 2026 |
| Orchid Property Limited | Real estate | 2024 |
| Orchid Utilities Ltd | Construction | 2023 |
| Orchstar Ltd | Information & communication | 2025 |
| ORD NW Limited | Administrative & support | 2026 |
| Ordello Ltd | Information & communication | 2026 |
| Order & Chaos Agency Ltd | Professional & scientific | 2024 |
| Ordinto Investments | Financial services | 1976 |
| Oregon & Ratcliffe Ltd | Real estate | 2012 |
| Orelian Ltd | Information & communication | 2026 |
| Oreo PIP Limited | Professional & scientific | 2026 |
| Orez One Limited | Professional & scientific | 2025 |
| Organic Dyes & Botanicals UK Ltd | Manufacturing | 2022 |
| Organic Life Ltd | Wholesale & retail | 2023 |
| Organic Projects Ltd. | Professional & scientific | 2011 |
| Organic Provenance Ltd | Wholesale & retail | 2012 |
| Organic Strength Coaching Limited | Arts & recreation | 2023 |
| Organicurls Ltd | Manufacturing | 2024 |
| ORGANON85 Limited | Hospitality | 2018 |
| ORH Consulting Limited | Information & communication | 2014 |
| Orhan Flooring Limited | Construction | 2025 |
| Orial Ltd | Wholesale & retail | 2023 |
| Oriel 14 (1) Ltd | Real estate | 2019 |
| Oriel 14 (2) Limited | Extraterritorial | 2019 |
| Orient Continental Ltd | Hospitality | 2026 |
| Oriental Fufu Ltd | Wholesale & retail | 2021 |
| Oriental Security Systems Limited | Administrative & support | 1982 |
| Oriental Supply (UK) Ltd | Wholesale & retail | 2024 |
| Origen DE Colombia Investments LLP | | 2025 |
| Origin Event Group Ltd | Administrative & support | 2026 |
| Origin Fire Safety Limited | Construction | 2023 |
| Origin Gym Ltd | Arts & recreation | 2018 |
| Origin Kicks Ltd | Wholesale & retail | 2018 |
| Origin Retail Ltd | Wholesale & retail | 2024 |
| Origin Technical Services Ltd | Other services | 2015 |
| Original Hairdressers Ltd | Other services | 2020 |
| Origym Centre of Excellence Limited | Education | 2015 |
| Origym Group Limited | Arts & recreation | 2016 |
| Orion & NA Properties Ltd | Real estate | 2024 |
| Orion Forge Supply Continulm Limited | Wholesale & retail | 2025 |
| Orion Group LVP Ltd | Real estate | 2022 |
| Orion Management Services Ltd | Other services | 2019 |
| Orion Paints Limited | Manufacturing | 1989 |
| Orion Realtors Ltd | Real estate | 2025 |
| Orion Services Limited | Professional & scientific | 1998 |
| ORJ2 Consulting Limited | Professional & scientific | 2023 |
| Orka Manchester Limited | Financial services | 2024 |
| Orkans International Education Systems Private Limited | Education | 2019 |
| Orlando Holiday Rental Homes UK Limited | Real estate | 2011 |
| Orlowski 2020 Ltd | Transport & logistics | 2020 |
| Orme Civils Ltd | Construction | 2025 |
| Ormond Properties Limited | Real estate | 2005 |
| Ormskirk Catering (NW) Ltd | Hospitality | 2020 |
| Ormskirk Court Hotel Limited | Hospitality | 2018 |
| Ormskirk Motorfest Limited | Arts & recreation | 2018 |
| Ormskirk Self Storage Ltd | Real estate | 2026 |
| Ornate Elegance Ltd | Wholesale & retail | 2025 |
| Oromo Consultants Ltd | Other services | 2023 |
| Orpheus Touring Ltd | Information & communication | 2012 |
| Orrag Logistics Ltd | Transport & logistics | 2025 |
| Orrell Cafe Limited | Hospitality | 2016 |
| Orrell Lane Store Ltd | Wholesale & retail | 2026 |
| Orrell Park Heating Solutions Ltd | Construction | 2025 |
| Orrell Park Hotel Limited | Hospitality | 2017 |
| Orrell Park Motorcycles Ltd | Wholesale & retail | 2004 |
| Orrell Road Limited | Real estate | 2024 |
| Orrell Tandoori Ltd | Hospitality | 2025 |
| Orrett Services Limited | Health & social care | 2013 |
| ORS Real Estate Limited | Real estate | 2025 |
| ORS Telecoms Ltd | Information & communication | 2019 |
| Ortho Needs Limited | Health & social care | 2023 |
| Orthopaedicfoot Limited | Health & social care | 2016 |
| Orthotic Products Ltd | Wholesale & retail | 2019 |
| Orthotutor Limited | Education | 2024 |
| Orton Developments Limited | Real estate | 1997 |
| Orwel Road Ltd | Construction | 2017 |
| Orynx AI Ltd | Information & communication | 2025 |
| Oryx Property Ltd | Real estate | 2021 |
| OS News Agent Ltd | Wholesale & retail | 2018 |
| Osca Tradco Ltd | Administrative & support | 2016 |
| Oscar Barber Crosby Ltd | Other services | 2025 |
| Oscar Builds Limited | Information & communication | 2014 |
| Oscar Developments (Liverpool) Ltd | Extraterritorial | 2005 |
| Oscar Distributions Ltd | Wholesale & retail | 2026 |
| OSE Clean Energy AS a Service Ltd | Energy | 2022 |
| OSE Contract Services Ltd | Professional & scientific | 2023 |
| OSE KPP Holdco Ltd | Energy | 2022 |
| Oser Rever C.I.C. | Health & social care | 2019 |
| OSH Partners Ltd | Public administration | 2023 |
| OSJ Holdings Limited | Health & social care | 2016 |
| Oslife Stores Ltd | Wholesale & retail | 2021 |