| North Chilli Ventures Ltd | Other services | 2021 |
| North View Property - Holiday Lets Limited | Real estate | 2025 |
| North View Property Limited | Hospitality | 2021 |
| Northfield Farms Partnership Limited | Transport & logistics | 2015 |
| Noveltygiftsuk Limited | Wholesale & retail | 2023 |
| Novu Developments Limited | Construction | 2018 |
| Npconsult Limited | Professional & scientific | 2026 |
| NPS Fencing & Countryside Management Limited | Construction | 2022 |
| NR Freeholders Ltd | Households | 2020 |
| NS Cambridge Ltd | Manufacturing | 2020 |
| NTK Logistics Limited | Transport & logistics | 2010 |
| Nujig Ltd | Professional & scientific | 2013 |
| Number Twenty Ltd | Other services | 2025 |
| Nupremis Cambridge Limited | Professional & scientific | 2015 |
| O L Investments Limited | Real estate | 2020 |
| O'Shaughnessy Farriery Limited | Other services | 2014 |
| Oak Drive Management Ltd | Administrative & support | 2010 |
| Oak Farm Livery Yard Limited | Agriculture & fishing | 2021 |
| Oak Lane Business Park Limited | Real estate | 2017 |
| Oak Play Village Ltd | Health & social care | 2025 |
| Oakes and Watson Tree Surgery and Consultancy Limited | Administrative & support | 2017 |
| Oakington IT Services Limited | Information & communication | 2015 |
| Oath + Iron Limited | Arts & recreation | 2025 |
| Obinna Monye Public Relations & Management Ltd | Professional & scientific | 2018 |
| Occupation Road (Cambridge) Property Management Company Limited | Households | 2012 |
| OCW Trading Ltd | Wholesale & retail | 2021 |
| Oddcowcoffee Ltd | Hospitality | 2025 |
| OFF Grid Design Ltd | Professional & scientific | 2010 |
| OG Components Limited | Professional & scientific | 2012 |
| OGH Limited | Professional & scientific | 2012 |
| OIL & GAS Manufacturing Limited | Manufacturing | 2005 |
| OIL & GAS Measurement Limited | Professional & scientific | 2003 |
| OIL & GAS Services Limited | Extraterritorial | 1997 |
| OIL & GAS Systems Limited | Manufacturing | 1987 |
| Ojicoder Software Ltd | Information & communication | 2025 |
| OK Engineering Solution Ltd | Manufacturing | 2023 |
| Old Mill (Audley END Railway Station) Management Company Limited | Real estate | 2015 |
| Old Orchard Soham Road Two Ltd | Households | 2020 |
| Oliver Translations Limited | Professional & scientific | 1998 |
| Olkotec Limited | Administrative & support | 2012 |
| Ollington Jarvis Limited | Real estate | 2024 |
| Omatic Limited | Information & communication | 2000 |
| Omiya Consulting Limited | Professional & scientific | 2011 |
| Omniabi Ltd | Information & communication | 2025 |
| ON PAR Golf Driving Range Limited | Arts & recreation | 1999 |
| ON PAR Property Ltd | Real estate | 2024 |
| Oncolytika Ltd | Professional & scientific | 2010 |
| One Benson Place Limited | Administrative & support | 2017 |
| One Love Tennis C.I.C. | Education | 2023 |
| One Online Limited | Extraterritorial | 2005 |
| One World Connect Ltd | Information & communication | 2018 |
| Onset Limited | Arts & recreation | 2020 |
| Optimal Human Ltd | Health & social care | 2025 |
| Optimum Precision Engineering Holdings Limited | Financial services | 2015 |
| Optimum Precision Engineering Limited | Manufacturing | 1987 |
| Optimum Recycling Solutions Limited | Water & waste | 2019 |
| Optishell Consultancy Ltd | Professional & scientific | 2018 |
| Orange Gecko Marketing Ltd | Professional & scientific | 2024 |
| ORB Business Services Limited | Professional & scientific | 2003 |
| ORG Cleaning Ltd | Administrative & support | 2025 |
| Organic Garden Gastronomy Ltd | Hospitality | 2023 |
| Organic Pest Control Limited | Administrative & support | 1999 |
| Organic Pest Control Services Ltd | Administrative & support | 2025 |
| Orkester Consulting Limited | Professional & scientific | 2025 |
| Orkester Ltd | Professional & scientific | 2018 |
| Orryman Developments Limited | Construction | 2014 |
| Orson Grace Limited | Financial services | 2025 |
| Orvis Construction Limited | Construction | 2005 |
| Osborne's Garden Services Limited | Extraterritorial | 2016 |
| Otter Scapes Ltd | Wholesale & retail | 2020 |
| OUT of the Blue Consulting Limited | Financial services | 2003 |
| Outnumber Accounting Limited | Professional & scientific | 2025 |
| Owen & White Electrical Ltd | Construction | 2022 |
| OWL Carpentry Ltd | Construction | 2017 |
| OWL Technology Limited | Professional & scientific | 2000 |
| Owlee Software Ltd | Information & communication | 2020 |
| P & D Property Limited | Real estate | 2013 |
| P a Fineberg Limited | Professional & scientific | 2016 |
| P I M a Logistics Limited | Transport & logistics | 2026 |
| P Woods Construction Ltd | Construction | 2008 |
| P. B. Doyle | | 1999 |
| P.J. LEE & Sons (Farmers) Limited | Extraterritorial | 1983 |
| P.J. LEE & Sons Limited | Agriculture & fishing | 2019 |
| P.T.F.E. Parts Limited | Administrative & support | 2001 |
| PA Answer Limited | Administrative & support | 2008 |
| Paddock View Haddenham (Management Company) Limited | Households | 2023 |
| Paddocks House Management Company Limited | Professional & scientific | 1992 |
| Padnal Properties Ltd | Administrative & support | 2022 |
| Page Fine Jewellery Limited | Wholesale & retail | 2014 |
| Page Medical Communications Limited | Administrative & support | 2015 |
| Pajo Barbers Ltd | Other services | 2018 |
| Pakma Ltd | Transport & logistics | 2026 |
| Palace Green Homes Limited | Construction | 2016 |
| Palm Bulk Solutions Ltd | Other services | 2011 |
| Paramita Limited | Professional & scientific | 2008 |
| Parrott Investments Limited | Real estate | 2017 |
| Partner With PIP Limited | Professional & scientific | 2024 |
| Partnership Solutions Limited | Administrative & support | 2013 |
| Partridge & Partridge Consultancy Limited | Education | 2014 |
| Patnia Services Ltd | Professional & scientific | 2026 |