| Onyx Pictures Ltd | Information & communication | 2023 |
| On’S Heritage Care Ltd | Administrative & support | 2025 |
| OO Security Ltd | Administrative & support | 2024 |
| Oobz Ltd | Other services | 2025 |
| Oodles WOK Nottingham Limited | Hospitality | 2025 |
| Oosh Events Ltd | Administrative & support | 2023 |
| OP Mantra Ltd | Information & communication | 2024 |
| OP Property & Asset Management SPV Ltd | Real estate | 2026 |
| OPA Lele Ltd | Wholesale & retail | 2023 |
| Opal Crest Insights Ltd | Information & communication | 2025 |
| Opal Office Solutions Limited | Professional & scientific | 2017 |
| Opal Recruitment Services Ltd | Administrative & support | 2022 |
| Open Arms Organisation CIC | Hospitality | 2022 |
| Open Arms Support Services Ltd | Health & social care | 2013 |
| Open Coast Media UK Ltd | Information & communication | 2021 |
| Open Fit Limited | Wholesale & retail | 2020 |
| Open Homes Nottingham | Health & social care | 2005 |
| Open Intellect Limited | Information & communication | 2022 |
| Open Mind Solutions Ltd | Information & communication | 2020 |
| Open Retail Solutions Limited | Information & communication | 2003 |
| Open Road Simulation Ltd | Manufacturing | 2011 |
| Open Science Tools Limited | Professional & scientific | 2019 |
| Open Source Group Ltd | Administrative & support | 2023 |
| Open to ALL Kickboxing Ltd | Arts & recreation | 2025 |
| Open Wings Life and Work Skills Centre CIC | Education | 2021 |
| Openbook Insights Limited | Professional & scientific | 2026 |
| Opencore Ltd | Professional & scientific | 2023 |
| Openspec Consultancy Ltd | Professional & scientific | 2026 |
| Openwork Telecom Limited | Information & communication | 2019 |
| Openworld Food Safety Consortium Ltd | Hospitality | 2025 |
| Operation Diversity Limited | Education | 2015 |
| Operation Orphan | Health & social care | 2010 |
| OPH Fitness Limited | Education | 2026 |
| OPM Nottingham Ltd | Administrative & support | 2018 |
| OPS Workforce Consulting Ltd | Information & communication | 2026 |
| Opsimathy Ltd | Education | 2013 |
| Optidental Care Limited | Health & social care | 2025 |
| Optidrive Ltd | Professional & scientific | 2025 |
| Optiflyte Ltd | Professional & scientific | 2019 |
| Optiirent Ltd | Real estate | 2024 |
| Optik Forms Limited | Information & communication | 2025 |
| Optima Business Solutions Limited | Professional & scientific | 2025 |
| Optima Joinery Contractors Limited | Construction | 2002 |
| OPTIMA3 Limited | Information & communication | 2009 |
| Optimarc Ltd | Professional & scientific | 2010 |
| Optimate Technologies Ltd | Information & communication | 2024 |
| Optimise Marketing Limited | Professional & scientific | 2026 |
| Optimise Working Limited | Professional & scientific | 2017 |
| Optimum Apartments Ltd | Hospitality | 2019 |
| Optimum Business Supplies (Derby) Limited | Wholesale & retail | 2001 |
| Optimum Care Services (Nottm) Ltd | Health & social care | 2024 |
| Optimum Gains Ltd | Extraterritorial | 2009 |
| Optimum Leadership Services Limited | Professional & scientific | 2016 |
| Optimum Pitch Limited | Education | 2021 |
| Optio Systems Limited | Information & communication | 1979 |
| Options 4 Surfaces Ltd | Construction | 2024 |
| Optique Vision (Nottingham) Limited | Wholesale & retail | 2004 |
| Optitech Consultancy Limited | Information & communication | 2023 |
| Optivance Consultancy Group Ltd | Professional & scientific | 2026 |
| Optric Limited | Professional & scientific | 2014 |
| Optume Properties Limited | Real estate | 2020 |
| Optume Solutions Limited | Professional & scientific | 2019 |
| Opulen Property Group Limited | Real estate | 2025 |
| Opulence Barbering Limited | Other services | 2026 |
| Opulence Scope Ltd | Real estate | 2025 |
| Opulence UK Properties Ltd | Real estate | 2022 |
| Opus Contracting Limited | Water & waste | 2022 |
| Opus Lets Limited | Real estate | 2025 |
| Opus Properties Nottingham Limited | Hospitality | 2011 |
| OPV Kantacre Ltd | Professional & scientific | 2025 |
| Opzy Global Ltd | Other services | 2025 |
| Oracle Safety Associates Limited | Professional & scientific | 2002 |
| Oracle Signs Limited | Manufacturing | 2016 |
| Oracle Surveillance and Maintenance Limited | Construction | 2018 |
| Oracle Surveillance Ltd | Construction | 2009 |
| Orange Cat Crafts Ltd | Wholesale & retail | 2021 |
| Orange Crush Limited | Administrative & support | 2024 |
| Orange Leaf Products Limited | Wholesale & retail | 2024 |
| Orange Moon Childcare Community Interest Company | Health & social care | 2015 |
| Orange Moon Children Limited | Health & social care | 2022 |
| Orange Moon Training Limited | Education | 2015 |
| Orangedry Carpet and Upholstery Care Ltd | Administrative & support | 2021 |
| Orangery Concepts Ltd | Construction | 2024 |
| Orangetree Houseuk Ltd | Wholesale & retail | 2024 |
| Orangudann Limited | Information & communication | 2015 |
| Oranos Restaurant Limited | Hospitality | 2020 |
| Oranz (Nottingham) Ltd | Information & communication | 2004 |
| Orbal Ltd | Wholesale & retail | 2026 |
| Orbasso Ltd | Health & social care | 2022 |
| Orbit 365 Limited | Information & communication | 2022 |
| Orbit Legal Limited | Professional & scientific | 2020 |
| Orbit ME Limited | Financial services | 2020 |
| Orbita Group Ltd | Hospitality | 2019 |
| Orbital Communications Limited | Professional & scientific | 2012 |
| Orbital Group Holdings Limited | Financial services | 2020 |
| Orca Talker Ltd | Information & communication | 2021 |
| Orchard Close Holdings Limited | Financial services | 2020 |
| Orchard Court Residents Association Gedling Limited | Extraterritorial | 2009 |
| Orchard Educational Limited | Manufacturing | 2004 |
| Orchard Homes (Midlands) Limited | Extraterritorial | 2006 |