| MMP Royston Ltd | Manufacturing | 2022 |
| Mmpk Consulting Ltd | Other services | 2023 |
| Mneme Fabric Limited | Professional & scientific | 2025 |
| Mnjt Consulting Ltd | Professional & scientific | 2018 |
| Mobotix Service Limited | Extraterritorial | 2011 |
| Modalflux Limited | Information & communication | 2015 |
| MODE9 (UK) Limited | Wholesale & retail | 2001 |
| Model Gear Limited | Wholesale & retail | 2023 |
| Modern Slavery Intelligence Network Limited | Professional & scientific | 2023 |
| Module 200 Limited | Information & communication | 2015 |
| Molotov Pictures Ltd | Information & communication | 2016 |
| Monarchs Childcare Commercial Ltd | Real estate | 2019 |
| Monkey One Music Ltd | Arts & recreation | 2013 |
| Monkeymermaid Ltd | Hospitality | 2015 |
| Montacuto Limited | Administrative & support | 2016 |
| Moonleaf Reflexology Ltd | Health & social care | 2018 |
| Moore Than Just a Groom Ltd | Other services | 2023 |
| Morgan Davies London Limited | Wholesale & retail | 1999 |
| Morgan Keen Limited | Professional & scientific | 2003 |
| Morishac Limited | Professional & scientific | 2016 |
| Morregreen Holdings Ltd | Financial services | 2020 |
| Motorlet Limited | Administrative & support | 2016 |
| Moulian Media Ltd | Information & communication | 2018 |
| MPC Consulting Ltd | Professional & scientific | 2024 |
| Mpert Solutions Ltd | Professional & scientific | 2023 |
| MR MDF Ltd | Manufacturing | 2026 |
| MR. Chairman Limited | Administrative & support | 2000 |
| Mreddy Consulting Limited | Professional & scientific | 2020 |
| Mrpg Ltd | Hospitality | 2025 |
| MS Electrical Engineering Design Ltd | Professional & scientific | 2025 |
| Mscv Consulting Limited | Professional & scientific | 2025 |
| MSK Pro Services Ltd | Professional & scientific | 2018 |
| Mulberry Corner Developments Limited | Construction | 2017 |
| Mulberry Court Residents Association Limited | Households | 1987 |
| Multi-Care Community Services North Hertfordshire Ltd | Health & social care | 2021 |
| Mumford & Worrall Ltd | Administrative & support | 2023 |
| Mums Room Rental Ltd | Real estate | 2020 |
| Murdoch Consulting Limited | Professional & scientific | 2001 |
| Murray Wealth Management Ltd | Financial services | 2020 |
| MWJ Marketing Agency Ltd | Professional & scientific | 2023 |
| MWS Renovations Ltd | Construction | 2022 |
| Myles Court Freehold Limited | Real estate | 1994 |
| Mynott Property Ltd | Real estate | 2026 |
| Myrror Ltd | Health & social care | 2024 |
| N J Hawden Limited | Professional & scientific | 2016 |
| N R N Flooring Limited | Construction | 1999 |
| N.B. Accountancy Limited | Professional & scientific | 2009 |
| N.B. Personnel Limited | Administrative & support | 2009 |
| N.R.F. Contracting Services Ltd | Agriculture & fishing | 2006 |
| Naked EWE Ltd | Manufacturing | 2022 |
| Nash Close RTM Company Ltd. | Households | 2023 |
| National Generator Sales Ltd | Wholesale & retail | 2024 |
| Natsu Garden Ltd | Administrative & support | 2022 |
| Naturally Happy Dogs Ltd | Information & communication | 2010 |
| Naturally Healthy Dogs Ltd | Wholesale & retail | 2015 |
| Nature Nell and DR Dell CIC | Administrative & support | 2026 |
| Naturist Massage Limited | Extraterritorial | 2016 |
| Navigator Training Ltd | Education | 2025 |
| Naylors Timber Recovery Limited | Manufacturing | 1988 |
| NB. the Wellness Consultant Limited | Other services | 2018 |
| Neednowater Limited | Information & communication | 2009 |
| Neil Wise (Lettings) Ltd | Real estate | 2021 |
| Neil Wise (Royston) Ltd | Real estate | 2020 |
| Neil Wise Ltd | Real estate | 2019 |
| Nessie in ED CIC | Education | 2018 |
| Nestrove Properties Ltd | Extraterritorial | 2025 |
| NET Revolution Limited | Information & communication | 1999 |
| Nettingworth Limited | Professional & scientific | 2011 |
| Neurohub International Ltd | Other services | 2024 |
| New Art Club LLP | | 2004 |
| New Bridge Partnership Holding Company Limited | Professional & scientific | 2014 |
| New Dawn Blinds Ltd | Manufacturing | 2016 |
| New Farm Tower Limited | Real estate | 2020 |
| Newgate Civil Engineering Ltd | Construction | 2021 |
| Newmans Close Management Company Ltd | Households | 2005 |
| Newsells Park Estates Limited | Real estate | 2000 |
| Newsells Park Stud Limited | Agriculture & fishing | 2000 |
| Newsells Park Tech Ltd | Information & communication | 2022 |
| Newsells Park Winery Ltd | Agriculture & fishing | 2022 |
| Nexgen Project Solutions Ltd | Professional & scientific | 2025 |
| Nexus of Lighting Ltd | Information & communication | 2014 |
| NG Haulage Ltd | Water & waste | 2021 |
| NIC Bowman Consulting Ltd | Professional & scientific | 2022 |
| Nicklin Aero Limited | Professional & scientific | 2024 |
| Nigel Smith Properties Limited | Administrative & support | 2001 |
| Nightmare Insomnia Ltd | Information & communication | 2024 |
| Njservicesandsupply Ltd | Wholesale & retail | 2026 |
| NKT Financial Solutions Limited | Financial services | 2007 |
| NKT Legal Solutions Limited | Professional & scientific | 2017 |
| NLD (Operations) Ltd | Construction | 2015 |
| NLD (Rentals) Ltd | Construction | 2013 |
| NMA Estates Ltd | Construction | 2025 |
| NO Limits Exhibitions Limited | Professional & scientific | 1999 |
| NO Strings Attached Ltd | Manufacturing | 2000 |
| NO.3 Royston Ltd | Wholesale & retail | 2024 |
| Noble Surgical Services Ltd | Professional & scientific | 2022 |
| Nokweja Limited | Health & social care | 2014 |
| Norburys Building & Landscape Supplies Limited | Administrative & support | 2004 |
| Nordic Nails Ltd | Extraterritorial | 2025 |
| North END Business Consulting Ltd | Professional & scientific | 2025 |