| Msted Properties Ltd | Real estate | 2018 |
| Mtbm Lettings Ltd | Real estate | 2024 |
| Mtbm Ltd | Professional & scientific | 2021 |
| Muddy Paws Berkhamsted Limited | Wholesale & retail | 2019 |
| Mulberries Medical Ltd | Health & social care | 2022 |
| Muldon Properties Ltd | Real estate | 2025 |
| Mulkerrins Property Services Ltd | Construction | 2020 |
| Mundy Roofing Limited | Construction | 2017 |
| Muse Lifestyle Limited | Wholesale & retail | 2003 |
| Music 3.0 Limited | Information & communication | 2022 |
| Muswell Conversions Limited | Construction | 2026 |
| Muxu Media Ltd | Administrative & support | 2022 |
| MW Agri Limited | Agriculture & fishing | 2003 |
| My Garage Makeover (UK) Ltd | Other services | 2021 |
| My Pocket CMO Ltd | Information & communication | 2025 |
| Mybiscoff Homes Limited | Real estate | 2024 |
| Mybiscoff Limited | Professional & scientific | 2022 |
| Mygg Ltd | Real estate | 2023 |
| Myth Creative Ltd | Professional & scientific | 2021 |
| MYV Studios Ltd | Information & communication | 2024 |
| Natalie Shafii Ltd | Other services | 2022 |
| National Devops-Intelligence Agency Ltd | Administrative & support | 2017 |
| Nationwide Fleet Ltd | Administrative & support | 2010 |
| Native PR and Marketing Consultancy Limited | Professional & scientific | 2012 |
| Natural Born Thinkers Ltd | Professional & scientific | 2019 |
| Nbodyworx Soft Tissue Therapies Ltd | Health & social care | 2022 |
| Ne'Er DO Well Productions Ltd | Information & communication | 2013 |
| Neasham Vale Limited | Professional & scientific | 2019 |
| Necessary Biro Limited | Professional & scientific | 2017 |
| Neck-It IP Holding Co Ltd | Administrative & support | 2026 |
| Neighbourhood Fives Limited | Hospitality | 2025 |
| Neil Haldar Limited | Health & social care | 2019 |
| Nellie’S Fine Wine Bar Ltd | Hospitality | 2024 |
| Nest Away Ltd | Administrative & support | 2016 |
| Netivaleo Ltd | Information & communication | 2024 |
| Network ATP Ltd | Professional & scientific | 2022 |
| Neuro Physio Berkhamsted Limited | Health & social care | 2008 |
| New Level Hemel Limited | Real estate | 2006 |
| Newark-Upon-Trent Timber Supplies Limited | Wholesale & retail | 2025 |
| Newton Colmore Consulting Limited | Administrative & support | 2014 |
| Nexo Education Ltd | Administrative & support | 2024 |
| Next Aviation Systems Limited | Transport & logistics | 2024 |
| Next Level Business Ltd | Professional & scientific | 2024 |
| Next Steps Dyslexia Assessment Ltd | Education | 2026 |
| Nicely Done Ltd | Administrative & support | 2014 |
| Nicholas Phillips Designs Limited | Professional & scientific | 2023 |
| Nick Denham Building Contractor Ltd | Construction | 2017 |
| Nick Hastings Consulting Ltd | Health & social care | 2017 |
| Nicol Capital Limited | Administrative & support | 2014 |
| Nikon Investments Ltd | Real estate | 2006 |
| Nine Sky Ltd | Professional & scientific | 2019 |
| Nippers and Knapsacks Ltd | Information & communication | 2018 |
| NIU Capital (UK) Limited | Real estate | 2023 |
| Nivelo Design Limited | Professional & scientific | 2018 |
| NJW Media Consultants Limited | Professional & scientific | 2005 |
| NO Nonsense PR Limited | Professional & scientific | 2017 |
| Noimad Ltd | Real estate | 2021 |
| Nola London Ltd | Manufacturing | 2019 |
| Noodle K Hatfield Ltd | Hospitality | 2023 |
| Noreaster Refrigeration Ltd | Manufacturing | 2020 |
| Norman-Studio Ltd | Professional & scientific | 2025 |
| North Road Studio Ltd | Professional & scientific | 2020 |
| North View Homes Ltd | Construction | 2022 |
| NORTH20 Recruitment Ltd | Administrative & support | 2026 |
| Northridge Consultants Limited | Information & communication | 1996 |
| NU Folk Ltd | Wholesale & retail | 2021 |
| Nuad Boran Limited | Administrative & support | 2016 |
| Number 84 Ltd | Administrative & support | 2020 |
| Numi Scan (North London) Ltd | Health & social care | 2020 |
| Numi Scan Franchise Ltd | Administrative & support | 2021 |
| Numi Scan Ltd | Health & social care | 2016 |
| Numi Sign Ltd | Professional & scientific | 2013 |
| Nutri-Tech Amenity Ltd | Wholesale & retail | 2021 |
| Nxtep London Ltd | Arts & recreation | 2013 |
| O'Durand Property Development Limited | Construction | 2010 |
| Oak Recruitment Ltd | Administrative & support | 2021 |
| Oakham Scott Limited | Construction | 2025 |
| Oakleigh Heating Limited | Construction | 2015 |
| Oakleys Estate Agents Limited | Real estate | 2017 |
| Oakridge Recruitment Ltd | Administrative & support | 2022 |
| Oakwood Home Finance Ltd | Financial services | 2020 |
| Oakwood Property Solutions Ltd | Construction | 2008 |
| OAO Ltd | Professional & scientific | 2018 |
| OC Gripping Ltd | Information & communication | 2010 |
| OCB Coaching Limited | Professional & scientific | 2023 |
| Ociam Limited | Real estate | 2026 |
| Ockley 2025 Limited | Real estate | 2025 |
| OD Snooker Ltd | Arts & recreation | 2024 |
| Odjas Engineering Ltd | Information & communication | 2017 |
| ODO Vintage Ltd | Wholesale & retail | 2018 |
| Office Supplies Group Ltd. | Administrative & support | 1992 |
| OK to BE Different Ltd | Professional & scientific | 2024 |
| Old Castle Flats Ltd. | Real estate | 1993 |
| Olfac Ltd | Professional & scientific | 2026 |
| OMD Design Limited | Arts & recreation | 2006 |
| Omob Ltd | Professional & scientific | 2025 |
| One TOO Property Investments Limited | Real estate | 2018 |
| ONE11 Consulting Ltd | Administrative & support | 2025 |
| Oneninefive Demand Ltd | Professional & scientific | 2025 |
| Onest Management Limited | Administrative & support | 2022 |