| Offa Bridge Limited | Financial services | 2023 |
| Offa Finco 1 Limited | Financial services | 2019 |
| Offa Finco 2 Limited | Financial services | 2022 |
| Offa Finco 3 Limited | Financial services | 2021 |
| Offa Finco 4 Limited | Financial services | 2024 |
| Offa Finco 5 Limited | Financial services | 2024 |
| Offa Finco 6 Ltd | Financial services | 2019 |
| Offa Finco 7 Ltd | Financial services | 2026 |
| Offa Group Holdings Limited | Financial services | 2022 |
| Offa Holdings Limited | Financial services | 2019 |
| Offa Mezz 1 Ltd | Financial services | 2022 |
| Offa Money Limited | Financial services | 2019 |
| Offa Money TOO Limited | Financial services | 2023 |
| Offa Operations Ltd | Financial services | 2018 |
| Offside Group Ltd | Hospitality | 2025 |
| Offtek Limited | Information & communication | 1996 |
| OG Plates Limited | Wholesale & retail | 2025 |
| Ogay Properties Ltd | Real estate | 2021 |
| OGL Property Investments Limited | Real estate | 2022 |
| Ogle Group Holdings Limited | Financial services | 2022 |
| OH Property Group Ltd | Real estate | 2026 |
| OHD Home Solutions Ltd | Real estate | 2025 |
| Ohdepartment Limited | Health & social care | 2019 |
| OHR Group Ltd | Hospitality | 2024 |
| OIK Strategy Limited | Administrative & support | 2011 |
| OIL Talent Solutions Ltd | Professional & scientific | 2019 |
| OJD (Chadwick END) Limited | Construction | 2025 |
| OK Jewelz Ltd | Wholesale & retail | 2024 |
| OKC Holdings Limited | Financial services | 2022 |
| OLA SF Limited | Wholesale & retail | 2026 |
| Olbre Business Solutions Ltd | Professional & scientific | 2022 |
| Old Silhillians Association Limited | Hospitality | 1965 |
| Old Spot PUB Company Limited | Hospitality | 2018 |
| Old Woodyard Developments Limited | Construction | 2023 |
| Oldacre Holdings Ltd | Construction | 2017 |
| Oldbury UK Limited | Manufacturing | 1982 |
| Olectrical Installations Ltd | Construction | 2026 |
| Olgio Balsall Limited | Other services | 2024 |
| OLI Luke Ltd | Information & communication | 2015 |
| Olive & Berry Grazing Limited | Hospitality | 2023 |
| Olive and Belle Properties Ltd | Real estate | 2025 |
| Oliver Family Workshop Limited | Extraterritorial | 2021 |
| Olivia FOX & Co Ltd | Hospitality | 2020 |
| Ollyo Ltd | Administrative & support | 2022 |
| OLT Invest Limited | Real estate | 2017 |
| Olton Branch Ltd | Hospitality | 2017 |
| Olton Brickwork Ltd | Construction | 2022 |
| Olton Bridge (Warwick Road) Limited | Households | 2006 |
| Olton Court Property Management Limited | Households | 2009 |
| Olton Damp Proofing Ltd | Construction | 2024 |
| Olton Driveways & Fencing Ltd | Administrative & support | 2023 |
| Olton Grounds,Limited | Construction | 1897 |
| Olton Health and Performance Ltd | Health & social care | 2022 |
| Olton Home & Garden Services Ltd | Administrative & support | 2026 |
| Olton Retail Ltd | Households | 2017 |
| Olton Solihull 888 Limited | Hospitality | 2026 |
| OM Solutions & Services Ltd | Information & communication | 2015 |
| Omaroza Beauty Limited | Other services | 2012 |
| Omaroza Laser Limited | Other services | 2012 |
| Omerta World Ltd | Wholesale & retail | 2021 |
| OMG Assets Limited | Real estate | 2021 |
| Omnia Construction Ltd | Construction | 2020 |
| Omnipresent International Limited | Wholesale & retail | 2016 |
| Omnis Group Services Limited | Professional & scientific | 2017 |
| Omsrisairam Ltd | Information & communication | 2016 |
| OMV Global Ltd | Wholesale & retail | 2020 |
| ON Air Audio Limited | Information & communication | 2014 |
| ON Device Solutions Limited | Information & communication | 2011 |
| ON Logistics Limited | Transport & logistics | 2004 |
| ON Point Staffing Ltd | Arts & recreation | 2016 |
| ON Site Resourcing Limited | Other services | 2011 |
| ON the Go Juice Limited | Wholesale & retail | 2026 |
| ON the Terraces Online Ltd | Wholesale & retail | 2021 |
| ON Your Radio Limited | Information & communication | 2021 |
| Onalti Limited | Wholesale & retail | 2019 |
| One 100 Ltd | Hospitality | 2019 |
| One Emergency Birmingham Limited | Health & social care | 2024 |
| One for the Road BAB Ltd | Hospitality | 2022 |
| One Group Holdings Limited | Real estate | 2024 |
| One Minute Silence Group Limited | Professional & scientific | 2004 |
| One Minute Silence Limited | Professional & scientific | 2003 |
| One Rosebery Road Limited | Households | 2016 |
| One Stop Mortgage Solutions Limited | Financial services | 2024 |
| One Stop Solihull Ltd | Wholesale & retail | 2024 |
| One Stop Touchwood Ltd | Wholesale & retail | 2025 |
| One World Development Associates Ltd | Professional & scientific | 2023 |
| ONE2ONE Brokers Limited | Financial services | 1987 |
| ONE2ONE Insurance Limited | Financial services | 2011 |
| Onecall Distribution Ltd | Wholesale & retail | 2018 |
| Onecold Ltd | Construction | 2005 |
| Onefix Services Limited | Construction | 2025 |
| Oneshop Limited | Manufacturing | 2026 |
| Onestopsurveys Ltd | Households | 2025 |
| Oneworld Utilities Solutions Ltd | Professional & scientific | 2023 |
| Onguard UK Limited | Information & communication | 2001 |
| Online EAR Shop Limited | Wholesale & retail | 2023 |
| Only Artscrafts Ltd | Wholesale & retail | 2024 |
| Onpoint EOT Limited | Administrative & support | 2025 |
| Onpoint Logistics Ltd | Transport & logistics | 1997 |
| Onpoint ST Ltd | Financial services | 2017 |