| Onevita Ltd | Real estate | 2015 |
| Onirise Ltd | Education | 2024 |
| Onsite Blast Services Limited | Extraterritorial | 2012 |
| Onstyle Lifting & Engineering Limited | Manufacturing | 2010 |
| Onyx Workwear Ltd | Wholesale & retail | 2021 |
| Oort Recruitment Ltd | Administrative & support | 2021 |
| OPA Consultants Ltd | Information & communication | 2011 |
| Open Harbor Care & Support Ltd | Health & social care | 2026 |
| Open Heart Care Services Ltd | Health & social care | 2022 |
| Open Space Property Developments Ltd | Real estate | 2024 |
| Opex Construction Ltd | Construction | 2023 |
| Optic Works Ltd | Construction | 2023 |
| Optical People Ltd | Health & social care | 2015 |
| Opulent Property Management Ltd | Real estate | 2026 |
| Orange Beam Productions Limited | Information & communication | 2012 |
| Orange Hawk Property Ltd | Real estate | 2018 |
| Orbit Taxi Services Limited | Transport & logistics | 2024 |
| Orca Core Ltd | Information & communication | 2025 |
| Orca Projects Ltd | Professional & scientific | 2021 |
| Orca Property & Electrical Services Ltd | Real estate | 2025 |
| Orchid Massage Limited | Arts & recreation | 2025 |
| ORD Consultants Limited | Professional & scientific | 2010 |
| Orderbeach Limited | Information & communication | 1983 |
| Ordina Group Ltd | Professional & scientific | 2026 |
| Organic Vision International Ltd | Manufacturing | 2012 |
| Organiccbd.Earth Ltd | Agriculture & fishing | 2020 |
| Organza Designers Ltd | Wholesale & retail | 2019 |
| Oriental Barlestone Limited | Hospitality | 2022 |
| Orientport Global Ltd | Wholesale & retail | 2025 |
| Origin China Home Antiques Limited | Wholesale & retail | 2026 |
| Original 10 Limited | Information & communication | 2013 |
| Orion ARC Ltd | Information & communication | 2025 |
| Orion Nebula Holdings Limited | Transport & logistics | 2025 |
| Orion Precision Testing Solutions Limited | Manufacturing | 2024 |
| Oroian Transport Limited | Transport & logistics | 2016 |
| Orton Marketing Limited | Administrative & support | 2013 |
| Oryx Restaurant Ltd | Wholesale & retail | 2024 |
| OS Eighty Seven Ltd | Health & social care | 2024 |
| Osin Healthcare Ltd | Health & social care | 2022 |
| Oskar Maria Ltd | Construction | 2019 |
| Otologic Limited | Health & social care | 2023 |
| Oudh Oasis Ltd | Information & communication | 2015 |
| Outdoor Furniture Hire Ltd | Hospitality | 2026 |
| Outdoor Structures UK Ltd | Wholesale & retail | 2026 |
| Outlook Landscaping Limited | Construction | 2022 |
| Outreach Consulting Limited | Professional & scientific | 2014 |
| Outside the Box Nuneaton & Bedworth CIC | Education | 2026 |
| Outstanding Care Providers Association Ltd | Health & social care | 2023 |
| Outstanding Care Providers Network Ltd | Health & social care | 2023 |
| Outstanding Homecare Providers Network Ltd | Health & social care | 2023 |
| Outstanding Supported Living Providers Network Ltd | Health & social care | 2023 |
| Oval Care Ltd | Health & social care | 2019 |
| Overnorf Communications Ltd | Information & communication | 2019 |
| Overton People Consulting Limited | Administrative & support | 2026 |
| Owens Property Investment Ltd | Real estate | 2023 |
| Owled Solutions Limited | Manufacturing | 2020 |
| OX Hayes Farm Management Company Limited | Households | 2023 |
| Oxby Birmingham Limited | Financial services | 2013 |
| Oxby Investments Limited | Administrative & support | 2013 |
| Oxby Warm Air Limited | Construction | 1967 |
| Oxhayes Farm Limited | Construction | 2020 |
| Oysterjam Limited | Professional & scientific | 2010 |
| OZ Kulhas Transport Ltd | Transport & logistics | 2018 |
| Ozirim Logistics Limited | Transport & logistics | 2019 |
| Ozzicozi Limited | Wholesale & retail | 2016 |
| O’Hara Enterprises Ltd | Information & communication | 2025 |
| P a W Solutions Limited | Agriculture & fishing | 2025 |
| P Bailey Renovations Limited | Construction | 2018 |
| P Griffiths Vehicle Services Limited | Wholesale & retail | 2012 |
| P Michelle Ltd | Real estate | 2015 |
| P Moore Construction Limited | Construction | 2012 |
| P T Traditional Meats Ltd | Wholesale & retail | 2018 |
| P&F UK Holdings Limited | Financial services | 2025 |
| P&J Properties (Midlands) Ltd | Real estate | 2023 |
| P&M Properties Invest Ltd | Real estate | 2019 |
| P&P Scrap Metal Trading Ltd | Transport & logistics | 2015 |
| P-Tech Ltd | Information & communication | 2002 |
| P.A.K.S. | Health & social care | 1992 |
| P.P. & B. (Hinckley) Limited | Wholesale & retail | 1978 |
| P.S. Accountancy Limited | Professional & scientific | 1997 |
| P1 Racevans Limited | Manufacturing | 2024 |
| Paappens Limited | Wholesale & retail | 2021 |
| Pacepta Properties Ltd | Real estate | 2024 |
| Paddock View (Galley Common) Management Company Ltd | Households | 2022 |
| Pafan Ltd | Real estate | 2025 |
| Pagwics Limited | Other services | 2021 |
| Pahuk Ltd | Health & social care | 2021 |
| PAK Rail Performance Limited | Administrative & support | 2014 |
| Pala Logistics Ltd | Transport & logistics | 2017 |
| Pallett Drive Day Nursery Ltd | Health & social care | 2015 |
| Palm Autos Ltd | Wholesale & retail | 2020 |
| Palme Ltd | Wholesale & retail | 2025 |
| Palmer Coleby House RTM Company Ltd | Households | 2014 |
| Palmer House Freehold Limited | Households | 2015 |
| Palmers Removals Limited | Transport & logistics | 2023 |
| Paloka Carpet & Upholstery Cleaning Ltd | Administrative & support | 2020 |
| Paloma Property Co Ltd | Real estate | 2022 |
| Pamal Transport Limited | Transport & logistics | 2023 |
| Pampervan Limited | Other services | 2020 |
| Pan-African Provisions Limited | Manufacturing | 2024 |