| New Horizons (Cambridge) Limited | Real estate | 2001 |
| New London Gate Limited | Administrative & support | 2014 |
| Newgate Management Ltd | Households | 2024 |
| Nexdor Developments (ST. Ives) Limited | Construction | 2015 |
| Nexdor Residential Limited | Households | 2020 |
| Next Comms. Limited | Information & communication | 2012 |
| Nexus Training Systems Limited | Professional & scientific | 2024 |
| NH Hotels Limited | Hospitality | 2019 |
| Nicholas Hythe Design & Build Limited | Wholesale & retail | 2021 |
| Nicholas Hythe Limited | Wholesale & retail | 2009 |
| Nick Brown (Tennis) Limited | Arts & recreation | 2005 |
| Niddocks Limited | Information & communication | 2003 |
| Nimet One Limited | Financial services | 2024 |
| NIX and H Limited | Hospitality | 2021 |
| NJH Digital Ltd | Professional & scientific | 2024 |
| Njorth BIO Science Limited | Professional & scientific | 2017 |
| NK Legal Consultancy Services Ltd | Professional & scientific | 2024 |
| North London Skydiving Centre Limited | Arts & recreation | 2009 |
| Nourish to Flourish MKD Limited | Health & social care | 2024 |
| Novo Learning Ltd | Education | 2020 |
| NRF Management Ltd | Professional & scientific | 2004 |
| NTH Degree Coaching Limited | Professional & scientific | 2008 |
| Ntrl Ltd | Wholesale & retail | 2025 |
| Nuts Bistro Ltd | Hospitality | 2021 |
| Nutwood Ventures Limited | Real estate | 2006 |
| NW1209 Ltd | Professional & scientific | 2019 |
| O&B Private Hire Limited | Transport & logistics | 2024 |
| Oak CG Limited | Financial services | 2021 |
| Oak CL Holdings Limited | Financial services | 2022 |
| Oak Leaf Living Ltd | Households | 2024 |
| Oakives Limited | Construction | 2024 |
| Oakley Keyholding Limited | Other services | 2009 |
| Oakwood Homes (Peterborough) Limited | Real estate | 2012 |
| Observatory Sciences Limited | Information & communication | 1998 |
| Ocean Building Company Ltd. | Construction | 2016 |
| Ocean Building Services Limited | Water & waste | 2013 |
| Ocean Challenge Limited | Education | 1997 |
| Ocean Galleries Limited | Wholesale & retail | 2012 |
| Ocean Management Limited | Professional & scientific | 2011 |
| Ocean Sports Equipment Limited | Wholesale & retail | 2014 |
| Ocean Supplies (ST Ives) Ltd | Wholesale & retail | 2002 |
| Octagon Outdoor Limited | Professional & scientific | 2015 |
| Odontoart Limited | Health & social care | 2014 |
| Official CUT AST Ltd | Other services | 2024 |
| Old Farm Courtiers Ltd | Households | 2016 |
| Old School Consultancy Limited | Professional & scientific | 2023 |
| Omega Courier Services Ltd | Transport & logistics | 2016 |
| Omie Ltd | Wholesale & retail | 2025 |
| ON a Mission Fitness Ltd | Arts & recreation | 2013 |
| ON Repeat FTW Limited | Administrative & support | 2020 |
| One 4 ALL (Holdings) Limited | Other services | 1995 |
| Onegrid Ltd | Information & communication | 2025 |
| Onzo (ST Ives) Limited | Hospitality | 2023 |
| Oowoah Limited | Information & communication | 2025 |
| OP Medical Ltd | Wholesale & retail | 2021 |
| Opals Living Limited | Real estate | 2017 |
| Open House Cambridgeshire Limited | Real estate | 2016 |
| Optanis Limited | Information & communication | 2026 |
| Opticable UK Limited | Wholesale & retail | 2023 |
| Optical Activity Limited | Manufacturing | 1973 |
| Optiplumb Limited | Construction | 2013 |
| Opus Materials Technologies Ltd. | Professional & scientific | 2014 |
| Orange Roofs Cornwall Ltd | Hospitality | 2015 |
| Orbit Transport Ltd | Transport & logistics | 2018 |
| Orchard Wholefoods Ltd | Wholesale & retail | 2024 |
| Organic Kitchen Products & Supplies Ltd | Manufacturing | 2019 |
| Origin Tyre Management Ltd | Wholesale & retail | 2025 |
| Oriole Global Health Limited | Health & social care | 2016 |
| Orton Plaza Management Limited | Real estate | 2015 |
| Osprey Car Company Limited | Manufacturing | 2022 |
| Otan Homes Ltd | Real estate | 2023 |
| OTS Truck Systems Limited | Manufacturing | 2015 |
| OTW Trading Limited | Wholesale & retail | 2015 |
| OUR Residences Ltd | Real estate | 2024 |
| OUT Music Group Ltd | Arts & recreation | 2025 |
| OUT Presents Ltd | Arts & recreation | 2024 |
| Outout Nightclub ST Ives Ltd | Information & communication | 2017 |
| Outout Nightclubs Ltd | Arts & recreation | 2019 |
| Outside Structure Solutions Limited | Construction | 2008 |
| Oxycarbon Limited | Professional & scientific | 2025 |
| Oxycarbonuk Ltd | Professional & scientific | 2023 |
| Oxycarbonuk Retail Ltd | Wholesale & retail | 2024 |
| P & a Construction (Cambridge) Limited | Construction | 2014 |
| P & a Properties (Cambridge) Ltd | Real estate | 2018 |
| P & R Plant Hire (Lincolnshire) Limited | Administrative & support | 2002 |
| P R Massala Ltd | Hospitality | 2010 |
| P&B Cladding Limited | Construction | 2011 |
| P.A.S Laundry Consultant Limited | Professional & scientific | 2024 |
| P.J. Steel Construction Limited | Manufacturing | 1994 |
| Paal Investments Ltd | Extraterritorial | 2012 |
| Pace Sheet Metal Limited | Manufacturing | 2014 |
| Paddock Fencing Limited | Manufacturing | 2015 |
| Palazzo Properties Limited | Construction | 2021 |
| Palingenesis Solutions Limited | Professional & scientific | 2017 |
| Pallet Sales UK Ltd | Wholesale & retail | 2011 |
| Paragon Crescent Ltd | Real estate | 2025 |
| Paragon Properties (Cambridge) Limited | Construction | 2016 |
| Park House (Stamford) Ltd | Construction | 2026 |
| Park View Residents (Needingworth) Ltd | Real estate | 2012 |
| Parkerrose Furniture Ltd | Manufacturing | 2026 |