| NJB Creative Ltd | Professional & scientific | 2024 |
| NJC Enterprises Limited | Real estate | 2015 |
| NJC Pubs and Clubs Limited | Hospitality | 2011 |
| NJS Automotive Ltd | Wholesale & retail | 2024 |
| NJT Group Holdings Ltd | Financial services | 2024 |
| Nkiru Ltd | Real estate | 2018 |
| Nkora Limited | Hospitality | 2015 |
| NKS Garden Design Ltd | Professional & scientific | 2021 |
| NMB Carpentry Limited | Manufacturing | 2021 |
| NN2 Kingsthorpe Ltd | Hospitality | 2025 |
| NO Limits Media Solutions Ltd | Information & communication | 2008 |
| Noble Design Limited | Construction | 2021 |
| Noble Plumbing and Heating Ltd | Construction | 2019 |
| Noble Protection Limited | Other services | 2011 |
| Nodeify Limited | Manufacturing | 2024 |
| Nois Crux Ltd | Information & communication | 2023 |
| Noiseorsun Ltd | Hospitality | 2026 |
| Noke Electrical Services Limited | Construction | 2014 |
| Noko Design Technology Manufacture Ltd | Professional & scientific | 2012 |
| Non-Trivial Ventures | Professional & scientific | 2025 |
| Nonza Solutions Ltd | Information & communication | 2018 |
| Nook Markyate Limited | Hospitality | 2023 |
| Noor Al-Quloob Ltd | Hospitality | 2025 |
| Noordwyk Ltd | Administrative & support | 2025 |
| Noorofficial UK Ltd | Wholesale & retail | 2025 |
| Nord Trading Ltd | Wholesale & retail | 2020 |
| Nordicninja VC Limited | Professional & scientific | 2023 |
| Nordikka Interiors Ltd | Wholesale & retail | 2017 |
| NOREE168 Ltd | Other services | 2021 |
| Normans Garages, Limited | Construction | 1942 |
| Norris Estates Ltd | Real estate | 2024 |
| North Atlantic Pelagic Advocacy Group | Other services | 2025 |
| North Barn Enterprises Limited | Other services | 2026 |
| North Cottages (Napsbury) Management Company Limited | Real estate | 1997 |
| North Fifth Eagles Ltd | Wholesale & retail | 2019 |
| North Herts & Beds Swimming LLP | | 2024 |
| North Lincs Investment Limited | Hospitality | 2018 |
| North Star Training Services Limited | Information & communication | 2022 |
| Northbound Marketing Ltd | Professional & scientific | 2026 |
| Northriver Limited | Construction | 1984 |
| Northtree Investment Management Ltd | Financial services | 2020 |
| Northwood (Hemel Hempstead) Limited | Real estate | 2023 |
| Northwood (Hemel) Limited | Real estate | 2023 |
| Northwood (ST Albans) Limited | Real estate | 2006 |
| Northwood Hospital Limited | Health & social care | 2023 |
| Notalman Consulting Limited | Professional & scientific | 2024 |
| Notch Hydro Limited | Professional & scientific | 2019 |
| Nothing Like Anything Limited | Professional & scientific | 2014 |
| Notion Recruitment Ltd | Administrative & support | 2025 |
| Nourbel UK Ltd | Administrative & support | 2011 |
| Nouveau Change Consulting Ltd | Professional & scientific | 2016 |
| Nova Niche Ltd | Wholesale & retail | 2025 |
| Novapharm Ltd | Manufacturing | 2025 |
| November Zulu Limited | Arts & recreation | 2007 |
| Novitas Fintech Advisers Ltd | Financial services | 2018 |
| NOW IS NOW Limited | Professional & scientific | 2023 |
| NOW WE CAN Ltd | Education | 2021 |
| NPA Health Education Foundation | Education | 1989 |
| Nphconsult Limited | Professional & scientific | 2020 |
| NRW Cleaning Services Ltd | Administrative & support | 2024 |
| NSA & NN Ltd | Professional & scientific | 2016 |
| NSK Medical Writing Limited | Information & communication | 2017 |
| NT Coaching and Consultancy Ltd | Professional & scientific | 2023 |
| Ntech Ltd | Information & communication | 2016 |
| Nu-Style Bathrooms & Interiors Limited | Wholesale & retail | 2026 |
| NUB Films Ltd | Information & communication | 2024 |
| NUB Music Ltd | Information & communication | 2013 |
| Nuclear Fabrications UK Limited | Extraterritorial | 2015 |
| Nudge Pet Wellness Ltd | Manufacturing | 2026 |
| Nudge Settle Ltd | Manufacturing | 2026 |
| Nugenmusic Limited | Information & communication | 2024 |
| NUK Properties Limited | Real estate | 2023 |
| Number 4 High Street Limited | Construction | 2012 |
| Number 7 Music (ST Albans) Ltd | Education | 2012 |
| Number One Athlete Limited | Education | 2025 |
| Number One Kitchen Limited | Hospitality | 2025 |
| Number Two Kitchen Ltd | Education | 2024 |
| Numerus Management Services Limited | Real estate | 2017 |
| Numerus Payroll Services Limited | Information & communication | 2013 |
| Numidus Ltd | Wholesale & retail | 2021 |
| Numinous Music Limited | Extraterritorial | 1999 |
| Numstack Consultants Ltd | Information & communication | 2025 |
| Nurture Business Group Limited | Professional & scientific | 2019 |
| Nuvana Touch Limited | Other services | 2025 |
| NXT Holdings Ltd | Financial services | 2021 |
| Nxtgen Activities Ltd | Education | 2025 |
| Nyne LLP | | 2021 |
| O Kotori Services Ltd | Construction | 2018 |
| O'Mahony Contracts (UK) Ltd | Construction | 2016 |
| O.B.H Matter Ltd | Manufacturing | 2025 |
| O.R.T Consulting Ltd | Professional & scientific | 2014 |
| Oak Point Court (Hillingdon) Management Limited | Construction | 2018 |
| Oak Tree Beef Ltd | Agriculture & fishing | 2023 |
| Oakbridge Homes (Group) Ltd | Construction | 1986 |
| Oakbridge Homes Limited | Construction | 1993 |
| Oakdell Limited | Construction | 1992 |
| Oakerfelt Ltd | Professional & scientific | 2016 |
| Oakes Property Developers Limited | Construction | 2017 |
| Oakhill Civil Engineering Limited | Construction | 1986 |
| Oaklands (ST. Albans) Management Limited | Households | 1999 |