| Neurostars Tutors Ltd | Education | 2025 |
| New British Film Company Limited | Information & communication | 2017 |
| New Dawn Innovations Ltd | Wholesale & retail | 2011 |
| New Gourmet Oriental Alton Ltd | Hospitality | 2018 |
| New Laliguras Limited | Hospitality | 2022 |
| New SWP Limited | Wholesale & retail | 2009 |
| New World Plants Limited | Other services | 1997 |
| Newark (T) Hairdressing Limited | Other services | 2012 |
| Newbury (T) Hairdressing Limited | Other services | 1998 |
| Newcastle Under Lyme (T) Hairdressing Limited | Other services | 2013 |
| Newcastle Upon Tyne (T) Hairdressing Limited | Other services | 2005 |
| Newkoz Ltd | Professional & scientific | 2012 |
| Newmarket (T2) Hairdressing Limited | Other services | 2016 |
| Newmarket (T3) Hairdressing Limited | Other services | 2025 |
| Newnham Associates Limited | Information & communication | 2000 |
| Newshound Communications Limited | Other services | 2006 |
| Nexaform Ltd | Information & communication | 2025 |
| Nexo HR Limited | Administrative & support | 2025 |
| Nicholas Lees Ltd | Arts & recreation | 2025 |
| Nick Marshall Landscapes Limited | Administrative & support | 2003 |
| Nick Mills Forestry Limited | Agriculture & fishing | 2008 |
| Nigel Green Wealth Management Limited | Administrative & support | 2005 |
| Nilam Ltd | Other services | 2019 |
| Nimblecast Ltd | Information & communication | 2024 |
| Nine Ascension Studios Ltd | Information & communication | 2025 |
| Nine Energy Services Limited | Education | 2025 |
| NK Accountancy Limited | Professional & scientific | 2015 |
| NLS Fabrications Limited | Manufacturing | 2008 |
| NM Editor Limited | Information & communication | 2023 |
| NO Shame Ltd | Other services | 2019 |
| Noar IP Limited | Administrative & support | 2024 |
| Noar, Limited | Professional & scientific | 2016 |
| NOI Publishing Limited | Manufacturing | 2006 |
| Norlan Resources Limited | Real estate | 1998 |
| Normandy Developments Limited | Construction | 1986 |
| NORMANDY94 Ltd | Households | 2016 |
| Norsin Ltd | Manufacturing | 2025 |
| North Audley Freehold Limited | Real estate | 2005 |
| North Audley Street (T) Hairdressing Limited | Other services | 2020 |
| North Hants Agricultural Contracting Limited | Agriculture & fishing | 2017 |
| Northanger House (Alton) Residents Management Company Limited | Households | 2019 |
| Northcroft Films Limited | Information & communication | 2000 |
| Northcroft Golf (2014) Limited | Manufacturing | 2014 |
| Northview Holdings (UK) Limited | Financial services | 2025 |
| Norton Place Pictures Limited | Information & communication | 2017 |
| Norwich (T2) Hairdressing Limited | Other services | 2024 |
| Nosh Fine Catering Ltd | Hospitality | 2013 |
| Notre Marque Ltd | Information & communication | 2020 |
| Nova Computing Limited | Information & communication | 2024 |
| Nova Vitae Holdings Ltd | Real estate | 2024 |
| Novus Europe Ltd | Administrative & support | 2020 |
| Ntnv Limited | Professional & scientific | 2023 |
| Nuage Communications Limited | Information & communication | 2013 |
| Nulook Energy Solutions Ltd | Construction | 2025 |
| Number Forty Two Limited | Professional & scientific | 2014 |
| Nuove Energie UK Limited | Manufacturing | 2017 |
| Nuvola Technology Solutions Limited | Wholesale & retail | 2025 |
| NXT LVL Group Limited | Professional & scientific | 2024 |
| NYE Brothers Ltd | Wholesale & retail | 2023 |
| O.B. Cameras Limited | Professional & scientific | 2012 |
| O.R.C.A. (Portsmouth) Limited | Wholesale & retail | 1988 |
| Oakley Green Management Limited | Real estate | 2024 |
| Oakley Property Investments Limited | Real estate | 2019 |
| Oakpath Financial Planning Ltd | Financial services | 2021 |
| Oaktree Capital Investment Ltd | Construction | 2025 |
| Oasis Diving Limited | Arts & recreation | 2014 |
| Oast House Management Company (Alton) Limited | Real estate | 2016 |
| Obsidian Security Services Ltd | Administrative & support | 2022 |
| Oceanspan Ltd | Real estate | 2001 |
| Octave Associates Limited | Information & communication | 1987 |
| ODC Medical Limited | Health & social care | 2008 |
| Odiham Motorcycle Club C.I.C. | Arts & recreation | 2017 |
| Odyssiant.Ai Limited | Information & communication | 2025 |
| Officeco Ltd | Administrative & support | 2023 |
| OIL Loss Solutions Ltd | Professional & scientific | 2021 |
| Old Odiham Services Ltd | Hospitality | 2013 |
| Old Rectory Gardens Thurlestone Limited | Households | 1999 |
| Old Sidings Management Company Limited | Professional & scientific | 2009 |
| Old Theatre 3 Limited | Information & communication | 2017 |
| Oldlands Farm Limited | Construction | 2017 |
| Olivers Consulting Limited | Professional & scientific | 2024 |
| Olivia Farming Holdings Limited | Agriculture & fishing | 2005 |
| Olivia Langmead Farming Limited | Agriculture & fishing | 2005 |
| Ollie Porter Photography Limited | Professional & scientific | 2023 |
| One Circle Financial and Technologies Ltd | Professional & scientific | 2025 |
| One Circle Global Trading & Technologies Limited | Professional & scientific | 2025 |
| Onespace Interiors Limited | Construction | 2025 |
| Onlooker Ltd | Information & communication | 2023 |
| Opticalnet Ltd | Administrative & support | 2011 |
| OPTIMIZE3D Ltd | Information & communication | 2018 |
| Optimus Consult Ltd | Professional & scientific | 2023 |
| Orchard Property Investments Limited | Real estate | 2007 |
| ORE Roofing & Cladding Ltd | Construction | 2024 |
| Organ Design Limited | Manufacturing | 2012 |
| Oriel Court (Plot 8) Limited | Real estate | 1993 |
| Origin Architecture Ltd. | Professional & scientific | 2015 |
| Orwo Film Distribution Limited | Arts & recreation | 2023 |
| Osgoods Limited | Wholesale & retail | 2010 |
| Osico Limited | Wholesale & retail | 2021 |
| Othland Ltd | Education | 2021 |