| New World Builders Limited | Construction | 1989 |
| New World Property Development Limited | Construction | 2000 |
| New Writtle Street (One) Management Company Limited | Households | 1994 |
| Newdecade Audio Visual Limited | Administrative & support | 2010 |
| Newmans Court (Numbers 8 & 9) Company Limited | Households | 2010 |
| Newport Engineering Limited | Professional & scientific | 2005 |
| News & Media Limited | Information & communication | 1969 |
| Nexifly UK Vape Ltd | Wholesale & retail | 2025 |
| Nexroc Advisory Limited | Professional & scientific | 2023 |
| Nextrasoft Limited | Information & communication | 2002 |
| Nextvax Ltd | Health & social care | 2018 |
| Nexum Fire & Security Limited | Construction | 2026 |
| Nexus-Academy Ltd | Education | 2025 |
| NFG Bronze Ltd | Arts & recreation | 2005 |
| Nicetouch IT Ltd | Information & communication | 2022 |
| Nicholas Ruddick Limited | Information & communication | 2020 |
| Niclex Ltd | Information & communication | 2013 |
| Nicola Lawrence Limited | Professional & scientific | 2018 |
| Nicole Danielle Ltd | Professional & scientific | 2021 |
| Nightingale Place Management Company Limited | Households | 1994 |
| Niiche Ltd | Construction | 2024 |
| NIX PIX Ltd | Information & communication | 2015 |
| NJG Healthcare Limited | Health & social care | 2015 |
| NNH1 Limited | Administrative & support | 2016 |
| NO Comment Legal Services Ltd | Professional & scientific | 2012 |
| NO.4 KC Limited | Real estate | 2015 |
| NO1 Training Company Limited | Professional & scientific | 2023 |
| Nobesity Ltd | Education | 2018 |
| Noctua Fire & Security Ltd | Administrative & support | 2026 |
| Noobee Ltd | Information & communication | 2024 |
| Nordec Investment Company Limited | Financial services | 2023 |
| Nordec Properties Limited | Real estate | 2024 |
| Norman Technical Management Services Ltd | Information & communication | 2023 |
| Norris Works Management Company Limited | Households | 2006 |
| North 2 South Media Ltd | Information & communication | 2018 |
| North Hants Roofing (Central) Limited | Construction | 2009 |
| North Road Hertford Management Company Ltd | Households | 2018 |
| North Seventeen Ltd | Financial services | 2022 |
| Northern Events Limited | Arts & recreation | 2020 |
| Northfield Restoration Studio Ltd | Other services | 2026 |
| Norton Hydraulics Limited | Manufacturing | 1967 |
| Nortonsport Ltd | Arts & recreation | 2016 |
| Norwich River Limited | Construction | 2019 |
| Nothing Unwanted Ltd | Information & communication | 2025 |
| Noucare Partners Ltd. | Administrative & support | 2019 |
| Nouvita Healthcare Ltd | Financial services | 2010 |
| Nouvita Limited | Health & social care | 2007 |
| Nova Care Services Ltd | Public administration | 2022 |
| Novocasa Limited | Construction | 2021 |
| Novus Precision Ltd | Professional & scientific | 2023 |
| Nowdesk Ltd | Information & communication | 2026 |
| NTN Limited | Hospitality | 2010 |
| NU Marketing Services Ltd | Professional & scientific | 2024 |
| Nubo Mortgages Ltd | Financial services | 2024 |
| Number One Port Hill Limited | Hospitality | 2011 |
| Nursery Fresh Ltd | Wholesale & retail | 2008 |
| Nutricare Fertilisers Limited | Administrative & support | 2013 |
| Nutrinovo Limited | Wholesale & retail | 2008 |
| Nyda NAK (UK) Limited | Wholesale & retail | 2025 |
| O J P Contracts (Holdings) Ltd | Financial services | 2024 |
| O J P Contracts Ltd | Agriculture & fishing | 2017 |
| O R C Printwear Promotions Limited | Wholesale & retail | 2006 |
| Oak Carter Limited | Construction | 2020 |
| Oake Construction Limited | Construction | 2011 |
| Oakheath Builders Limited | Professional & scientific | 2012 |
| Oaklands Engineering Limited | Manufacturing | 1998 |
| Oaklea Gardens Residents Limited | Households | 2007 |
| Oakley Operations Limited | Administrative & support | 2023 |
| Oakmont Solutions Ltd | Administrative & support | 2021 |
| Oaks Construction Group Ltd | Construction | 2026 |
| Oaksbuild Limited | Construction | 2019 |
| Occam Networks Limited | Professional & scientific | 2016 |
| Oceaa Ltd | Construction | 2007 |
| Oceaa Marketing Ltd | Extraterritorial | 2011 |
| Ocean Industrial Cleaning Limited | Administrative & support | 2013 |
| Ocho Ocho Limited | Agriculture & fishing | 2020 |
| Octad Recruitment Ltd | Administrative & support | 2009 |
| Octobersong Limited | Professional & scientific | 2016 |
| Odette Beauty Limited | Wholesale & retail | 2015 |
| Office Copiers Limited | Wholesale & retail | 2017 |
| Offshore Estate Planning Ltd | Financial services | 2022 |
| Ofix Limited | Construction | 2005 |
| OFM Investments Ltd | Real estate | 2016 |
| OFM Plumbing Ltd | Construction | 2020 |
| Ofthalmos UK Ltd | Health & social care | 2022 |
| OJR Transport and Consultancy Limited | Transport & logistics | 2017 |
| Old Aeroworks Management Limited | Households | 2002 |
| Old Cross Wharf Management Limited | Real estate | 2003 |
| Oliver LEE Plumbing and Heating Limited | Construction | 2023 |
| Olseen Property Maintenance Limited | Construction | 2016 |
| Olseen Roofing Ltd | Construction | 2015 |
| OM & V Property Services Limited | Real estate | 2016 |
| Omega Maltings Management Company Limited(The) | Households | 1985 |
| Omep Limited | Professional & scientific | 2021 |
| OMH Care Ltd | Hospitality | 2011 |
| Omsin's Limited | Hospitality | 2018 |
| One Concierge Limited | Administrative & support | 2017 |
| One for the Birds Limited | Professional & scientific | 2019 |
| One Hundred and SIX Lexham Gardens Limited | Households | 1982 |
| One Life Legacy CIC | Other services | 2025 |