| North Warwickshire Travel Ltd | Transport & logistics | 2006 |
| North West Wellness Limited | Health & social care | 2022 |
| Northbridge Machinery Limited | Manufacturing | 2005 |
| Northgate Flooring Company Ltd | Construction | 2018 |
| Northstar Engineering Limited | Professional & scientific | 2024 |
| Northwood (Tamworth & Lichfield) Ltd | Real estate | 2010 |
| Norton Canes Boat Services Limited | Manufacturing | 2015 |
| Norton Canes Boatbuilders Ltd | Manufacturing | 2014 |
| Norton Equipment Sales Limited | Wholesale & retail | 2015 |
| Notleks Communications Ltd | Information & communication | 2017 |
| Nouvelle Digital Ltd | Information & communication | 2025 |
| Nova Nest Luxury Limited | Other services | 2025 |
| Nporium Ltd | Professional & scientific | 2022 |
| NR Sweet & Sons Ltd | Transport & logistics | 2023 |
| NTN Construction Limited | Construction | 2019 |
| NTS Finance Limited | Administrative & support | 2026 |
| Nu-Style Holdings Limited | Wholesale & retail | 2002 |
| NUH Car Wash Ltd | Other services | 2026 |
| Number 6 Management Limited | Professional & scientific | 2020 |
| Nuvera Health Ltd | Professional & scientific | 2025 |
| Nuvo Medispa Ltd | Other services | 2023 |
| NW Home Services (Midlands) Limited | Real estate | 2025 |
| O & S Accounting Ltd | Professional & scientific | 2019 |
| O.C.K.O. Transport Ltd | Transport & logistics | 2015 |
| Oak Tree Court Management (Polesworth) Limited | Households | 2011 |
| Oakdene Boarding Limited | Other services | 2024 |
| Oakdene Developments (Midlands) Limited | Real estate | 1997 |
| Oakland Local Tree & Garden Care Ltd | Administrative & support | 2025 |
| Oakland Outdoor Leisure Limited | Wholesale & retail | 2021 |
| Oakleys Equestrian Ltd | Wholesale & retail | 2019 |
| Oakleytonifishing Ltd | Transport & logistics | 2025 |
| Oakline Roofing Ltd | Construction | 2025 |
| Oaktrees Healthcare Ltd | Health & social care | 2012 |
| Oakwell Green Property Limited | Real estate | 2025 |
| Obor Magazine Ltd | Wholesale & retail | 2024 |
| Obsidian Employee Benefits Limited | Other services | 2016 |
| Obsidian Financial Limited | Financial services | 2009 |
| Obsidian Games Ltd | Wholesale & retail | 2021 |
| OC Electrical (WM) Ltd | Construction | 2026 |
| Ocar Trading Ltd | Financial services | 2024 |
| Ocean House Building Management Limited | Households | 2023 |
| Octagon Facilities Management Ltd | Administrative & support | 2018 |
| Oddlys Limited | Wholesale & retail | 2026 |
| Odonnell Project Management Ltd | Professional & scientific | 2022 |
| Offa Properties Ltd | Real estate | 2023 |
| Office Business Supplies Limited | Wholesale & retail | 1996 |
| Offtrack Sales Limited | Education | 2026 |
| Ohain & Buchi Ltd | Wholesale & retail | 2019 |
| OIM Recruitment Ltd | Transport & logistics | 2018 |
| OJ & SAM Holdings Limited | Real estate | 2021 |
| Oldbbh Limited | Other services | 2013 |
| Oldfield Motor Sport Ltd | Arts & recreation | 2012 |
| Oldfield Sporting Management Limited | Arts & recreation | 2022 |
| Olympus Cctv Limited | Extraterritorial | 2004 |
| Olympus Commercial Supplies Ltd | Administrative & support | 1995 |
| Olympus Security Services Limited | Extraterritorial | 2003 |
| Olympus Therapies Ltd | Other services | 2015 |
| Omega Developments (Midlands) Ltd | Water & waste | 2022 |
| Omega Outdoor Adventure Ltd | Health & social care | 2018 |
| Omnitek Recruitment Limited | Administrative & support | 2026 |
| Omniwise Workplace Solutions Ltd | Wholesale & retail | 2018 |
| ON Pointe Photography Ltd | Professional & scientific | 2015 |
| ON Site Legend Ltd | Construction | 2026 |
| ON Site Trades Ltd | Administrative & support | 2025 |
| On-Time Haul Ltd | Transport & logistics | 2026 |
| One 2 One Accounting Solutions Limited | Professional & scientific | 2015 |
| One Above Gym Ltd | Arts & recreation | 2026 |
| One Media Shed Limited | Information & communication | 2014 |
| Oneplace Solutions Limited | Administrative & support | 2021 |
| Only Vip's Events and Promotions Limited | Information & communication | 2019 |
| ONTHECASE4U Ltd | Wholesale & retail | 2021 |
| Ontrack Performance Ltd | Arts & recreation | 2025 |
| Onyx Joinery Ltd | Construction | 2014 |
| Openfinal Property Management Limited | Households | 1989 |
| Openforeveryone Limited | Information & communication | 2010 |
| Opentransformers Ltd | Professional & scientific | 2026 |
| OPR Groundworks and Landscaping Limited | Administrative & support | 2025 |
| Optik Instruments Limited | Extraterritorial | 2018 |
| Optimal Installations Limited | Construction | 2023 |
| Optimal Solar & Commercial Clean Ltd | Administrative & support | 2015 |
| Optimum Build & Renovations Ltd | Other services | 2019 |
| Optimum Managed Services Ltd | Administrative & support | 2022 |
| Optimum Street Ltd | Real estate | 2026 |
| Optymum SS (UK) Ltd | Professional & scientific | 2024 |
| Orbik Limited | Manufacturing | 2024 |
| Orbital Industries Limited | Wholesale & retail | 2008 |
| Order Legend Ltd | Administrative & support | 2017 |
| Order Solutions Ltd | Information & communication | 2023 |
| Orellana Investments Ltd | Professional & scientific | 2024 |
| Orion Black Sea Ltd | Transport & logistics | 2026 |
| Orion High Voltage Engineering Limited | Construction | 2019 |
| Orion Manufacturing Services Ltd | Manufacturing | 2025 |
| Oris Aviation Ltd | Manufacturing | 2024 |
| Orranje Ltd | Administrative & support | 2024 |
| Ortholounger Ltd | Wholesale & retail | 2025 |
| Orviro Ltd | Wholesale & retail | 2025 |
| OSA Gateway Ltd | Financial services | 2025 |
| Osborne Commercial Investments Limited | Professional & scientific | 2008 |
| OSO Business Consulting Limited | Administrative & support | 2025 |
| Otaquas Training Ltd | Education | 2024 |