| NUM6ER Ltd | Hospitality | 2018 |
| Number Supermarket Limited | Information & communication | 2014 |
| Numera Analytics Ltd | Information & communication | 2024 |
| Nushot Ltd | Other services | 2016 |
| Nutriix Housing Support Ltd. | Real estate | 2017 |
| Nutriquarter Ltd | Wholesale & retail | 2025 |
| Nutrivity Ltd | Wholesale & retail | 2019 |
| NVK Limited | Health & social care | 2007 |
| NW Orthopaedics Ltd | Health & social care | 2023 |
| Nwfd Limited | Professional & scientific | 2022 |
| NWT Recruitment Limited | Administrative & support | 2017 |
| NYX Technologies Limited | Information & communication | 2011 |
| O&C Consultancy Ltd | Health & social care | 2025 |
| O&R Properties Ltd | Real estate | 2022 |
| O'Brien Property Solutions Limited | Real estate | 2021 |
| O'Connor Investments Ltd | Administrative & support | 2020 |
| O'Neill Property Investments Limited | Real estate | 2018 |
| O.P.P. (Westhulme) Limited | Real estate | 1999 |
| O.P.P. Investments Limited | Real estate | 1998 |
| O.S. Contracts Limited | Administrative & support | 2007 |
| Oak & Willow Care Services Ltd | Health & social care | 2021 |
| Oak Tree Solutions Ltd | Real estate | 2019 |
| Oakdale International Limited | Manufacturing | 2005 |
| Oakdene Accountancy Ltd | Professional & scientific | 2023 |
| Oakdene Bookkeeping Limited | Professional & scientific | 2024 |
| Oakfield Consultancy (UK) Limited | Professional & scientific | 2003 |
| Oakfield Mews Management (Sale) Limited | Households | 1973 |
| Oakland Financial Services Limited | Financial services | 2018 |
| Oakmere Fencing & Decking Limited | Construction | 2023 |
| Oakmere Landscaping Limited | Administrative & support | 2018 |
| Oakmere Management Company Limited | Households | 1991 |
| Oakwood Homes Construction Limited | Financial services | 1983 |
| Oakwood House Management Company (Alderley Edge) Limited | Households | 1997 |
| Oakwood Urban Build Limited | Construction | 2026 |
| OAS Esales Limited | Wholesale & retail | 2016 |
| Oasis Foods and Services Limited | Wholesale & retail | 2013 |
| Obiz Consulting Ltd | Information & communication | 2014 |
| Obliie Limited | Information & communication | 2024 |
| Occupancy Limited | Real estate | 2022 |
| Ocean International Trading Ltd | Wholesale & retail | 2017 |
| Octagon International Equity Ltd | Wholesale & retail | 2025 |
| Offsetpublications Limited | Information & communication | 2025 |
| Ohak Investment Limited | Real estate | 2019 |
| Ohana Sushi Ltd | Manufacturing | 2023 |
| OJ Yuki Limited | Arts & recreation | 2021 |
| OLA Eureka Ltd | Extraterritorial | 2021 |
| Old Hall Films Ltd | Information & communication | 2018 |
| Old Hall Rehab Ltd | Health & social care | 2026 |
| Old Trafford Spirits Ltd | Manufacturing | 2019 |
| Oldham Property Partnerships Limited | Construction | 1994 |
| Olifett Ltd | Transport & logistics | 2020 |
| Oliver SAN Limited | Other services | 1987 |
| Oma's Properties and Maintenance Ltd | Real estate | 2025 |
| Omdurman Ltd | Health & social care | 2026 |
| Omega Electrical Solutions Ltd | Construction | 2011 |
| Omni Clean Manchester Limited | Administrative & support | 2024 |
| Omni Developments (NW) Limited | Construction | 2018 |
| Omni Developments Manchester Limited | Construction | 2021 |
| Omni Properties Manchester Limited | Real estate | 2024 |
| Omnia Electrical Solutions Limited | Construction | 2017 |
| Omniquest Ltd | Wholesale & retail | 2024 |
| Omota Limited | Health & social care | 2024 |
| Omph Caring Hands Limited | Health & social care | 2024 |
| OMT Altrincham Ltd | Real estate | 2021 |
| ON a Tightrope Ltd | Hospitality | 2018 |
| ON the Table Ltd | Wholesale & retail | 2020 |
| One Collection Limited | Administrative & support | 2017 |
| One in a Million Store Limited | Wholesale & retail | 2023 |
| One Step Soft Limited | Information & communication | 2021 |
| One Transport Enterprise Limited | Transport & logistics | 2025 |
| One Two Three Four Five SIX Seven Eight Nine TEN Limited | Administrative & support | 2018 |
| One-Dream Limited | Real estate | 2020 |
| Oneasone Ltd | Wholesale & retail | 2024 |
| Onetec Technology Group Ltd | Information & communication | 2025 |
| Online Education Services Limited | Education | 2017 |
| Only Roofing Ltd | Construction | 2024 |
| Open Sports Ltd | Wholesale & retail | 2024 |
| Openanticheat Ltd | Extraterritorial | 2024 |
| Openehr CIC | Information & communication | 2019 |
| Openehr Foundation | Professional & scientific | 2003 |
| Ophod Limited | Wholesale & retail | 2025 |
| Ophtrex Ltd | Wholesale & retail | 2025 |
| OPO Property Ltd | Real estate | 2024 |
| Opportunus Ltd | Professional & scientific | 2008 |
| Optimum Freight Solutions Limited | Transport & logistics | 2015 |
| Opulon OTO Limited | Wholesale & retail | 2025 |
| Oraclean Ltd | Health & social care | 2010 |
| Oramis Digital Autopsy Limited | Health & social care | 2020 |
| Orange Street Services Limited | Professional & scientific | 2007 |
| Orbus Leisure Limited | Wholesale & retail | 2006 |
| Orca HMO Limited | Households | 2025 |
| Orion Consulting and Project Management Services Limited | Professional & scientific | 2026 |
| Orion Deals Ltd | Wholesale & retail | 2025 |
| Orly James Limited | Construction | 2018 |
| ORO Casa Ltd | Real estate | 2023 |
| Osbornes Removals and Storage Limited | Transport & logistics | 1983 |
| Osjen Homes Ltd | Real estate | 2024 |
| Ottimo Consulting Services Limited | Information & communication | 2022 |
| OUR Digital Team Limited | Information & communication | 2021 |
| OUT and About MCR Limited | Health & social care | 2014 |