| Norris White Services Ltd | Construction | 2019 |
| North Elms Property Limited | Real estate | 2018 |
| North London Scaffolding Co. Limited | Construction | 2025 |
| North Point Talent Limited | Professional & scientific | 2026 |
| North South Kitchens Ltd | Administrative & support | 2011 |
| North Watford Launderette Ltd | Administrative & support | 2018 |
| Northbank UK Properties Ltd | Real estate | 2021 |
| Northern Groundworks Ltd | Construction | 2019 |
| Northey Technologies Ltd. | Manufacturing | 1996 |
| Northfield Avenue (Holdings) Limited | Construction | 2004 |
| Northfield Avenue Properties Limited | Construction | 2006 |
| Northgate Immigration Law Ltd | Professional & scientific | 2026 |
| Northman Consultancy Ltd | Information & communication | 2022 |
| Northom Projects Limited | Manufacturing | 1993 |
| Northwatford Estates Ltd | Real estate | 2021 |
| Northwood Watford Ltd | Real estate | 2006 |
| Norwest Computer Services Limited | Professional & scientific | 1980 |
| Norwest Holst Civil Engineering Limited | Wholesale & retail | 1968 |
| Norwest Holst Construction Limited | Professional & scientific | 2001 |
| Norwest Holst Group Administation Limited | Extraterritorial | 1923 |
| Norwest Holst Soil Engineering Limited | Construction | 1970 |
| NOS 1-12 Oaklands (Watford) Residents Association Limited | Households | 1960 |
| Nosheen Limited | Hospitality | 2021 |
| NOT BAD for a Girl Limited | Administrative & support | 1997 |
| Notalkchauffeurs Limited | Transport & logistics | 2026 |
| Notley Developments Limited | Construction | 2020 |
| Nouveautech Limited | Information & communication | 2005 |
| Nova Haro Limited | Professional & scientific | 2014 |
| Nova Heating Solutions Ltd | Construction | 2019 |
| Nova NOW Ltd | Construction | 2025 |
| Nova Plan LP | | 2017 |
| Nova Summit Legacy Holdings Ltd | Wholesale & retail | 2025 |
| NOVA8 Consulting Limited | Professional & scientific | 2024 |
| Novabytz Technologies Limited | Information & communication | 2023 |
| Novacarats Limited | Information & communication | 2023 |
| Novafield Limited | Wholesale & retail | 2005 |
| Novapharma Ltd | Wholesale & retail | 2011 |
| Novateck Ltd | Information & communication | 2024 |
| Novator Pharma LLP | | 2011 |
| Novello Néos (Mortgages) Limited | Financial services | 2020 |
| Novello Néos (Network) Ltd | Other services | 2019 |
| Novesto Ltd | Transport & logistics | 2021 |
| Novopro Ltd | Wholesale & retail | 2012 |
| Novutech Ltd | Information & communication | 2025 |
| Nowherenear Group Limited | Financial services | 2020 |
| Nowherenear Labs Ltd | Information & communication | 2020 |
| Nowherenear Records Ltd | Information & communication | 2017 |
| NOX Construction Ltd | Financial services | 2023 |
| NOY Consulting Limited | Professional & scientific | 2020 |
| NPO Solutions Ltd | Information & communication | 2019 |
| Npsych Holding Company Limited | Financial services | 2022 |
| Npsych Investments Limited | Real estate | 2022 |
| NQ Consulting Limited | Professional & scientific | 2025 |
| NQ Recruitment Ltd | Administrative & support | 2015 |
| NRR Transport Ltd | Transport & logistics | 2024 |
| NRS Consultants Ltd | Professional & scientific | 2018 |
| NRS Education Limited | Professional & scientific | 2012 |
| NS Dhanani Properties Limited | Real estate | 2020 |
| NS Performance Ltd | Wholesale & retail | 2024 |
| NS Works Ltd | Information & communication | 2013 |
| Ns&M Limited | Administrative & support | 2014 |
| Nsix Solutions Ltd | Health & social care | 2021 |
| Nska Accountancy Ltd | Professional & scientific | 2020 |
| Nska Properties Ltd | Real estate | 2020 |
| Nskg Engineering Ltd | Administrative & support | 2016 |
| NSN Health Limited | Manufacturing | 2019 |
| Nsquared Rail Ltd | Professional & scientific | 2014 |
| Nstm Recruitment & Consultancy Ltd | Administrative & support | 2016 |
| Nstt Global 1 Limited | Wholesale & retail | 2022 |
| NT Management Services Limited | Administrative & support | 2015 |
| NTA Planning LLP | | 2021 |
| Ntek Holdings Limited | Information & communication | 2011 |
| NTI Corporation LLP | | 2013 |
| NTM Truck Ltd | Transport & logistics | 2025 |
| NTV Properties Limited | Real estate | 2000 |
| Nubari Property Limited | Real estate | 2020 |
| Nubio Holdings Ltd | Financial services | 2025 |
| Nubio Ltd | Construction | 2024 |
| Nufly Ltd | Professional & scientific | 2016 |
| Nulliton Limited | Manufacturing | 2025 |
| Numal Holdings Ltd | Financial services | 2025 |
| Numaterra Ltd | Information & communication | 2025 |
| Number 10 Sydney Street Management Company Limited | Households | 1979 |
| Number 58 Ltd | Hospitality | 2026 |
| Numbers (UK) Limited | Professional & scientific | 2005 |
| Numberscraft Services Limited | Professional & scientific | 2026 |
| Numidia Asset Management Ltd | Professional & scientific | 2024 |
| Nuna Care Agency Limited | Health & social care | 2023 |
| Nunong Limited | Hospitality | 2023 |
| Nuovo Creative Limited | Professional & scientific | 2023 |
| Nupax International Ltd | Administrative & support | 2021 |
| NUR FX Ltd | Financial services | 2024 |
| Nurosys Ltd | Information & communication | 2026 |
| Nursery and Childcare Ratings Ltd | Wholesale & retail | 2020 |
| Nurxmity Health Ltd | Information & communication | 2019 |
| Nuspy Ltd | Professional & scientific | 2015 |
| Nutrition Integrated Limited | Information & communication | 2017 |
| Nutrition Lounge Ltd | Arts & recreation | 2020 |
| Nutrition With Anjanee RD Ltd | Health & social care | 2022 |
| Nutu&Boss Ltd | Wholesale & retail | 2025 |