| Movat Limited | Hospitality | 2012 |
| MP Social Limited | Professional & scientific | 2022 |
| MR Painting Ltd | Construction | 2024 |
| MRB Rail Engineering Limited | Professional & scientific | 2019 |
| Mrbcam Limited | Construction | 2017 |
| Mrtd Limited | Administrative & support | 2018 |
| MT Films Limited | Information & communication | 2018 |
| MTR Living Limited | Real estate | 2015 |
| MTR Taylor & Sons Ltd | Construction | 2025 |
| MTZ Properties Limited | Real estate | 2022 |
| Mumaku Healthcare Limited | Health & social care | 2018 |
| Munch and Mend Ltd | Education | 2026 |
| Murtagh Studio Ltd | Professional & scientific | 2021 |
| Musical Technology Ltd | Manufacturing | 1997 |
| MV Academy Limited | Education | 2016 |
| MVM Mobile Vehicle Maintenance Ltd | Wholesale & retail | 2017 |
| My Head IS Spinning Ltd | Arts & recreation | 2014 |
| My Music Ltd | Arts & recreation | 2026 |
| Myalamer Limited | Wholesale & retail | 2016 |
| N R Daws Properties Limited | Real estate | 2014 |
| N.M.I. Safety Systems Limited | Manufacturing | 1977 |
| Narrative Creative Studios Ltd | Professional & scientific | 2023 |
| Natasha's Flowers UK Limited | Wholesale & retail | 2022 |
| Nationwide Debt Solutions Limited | Financial services | 1999 |
| Nazz Investments Limited | Real estate | 2020 |
| NBH Services (London) Limited | Professional & scientific | 2017 |
| Neal Trading Limited | Information & communication | 2019 |
| Neil Corner Haulage Limited | Transport & logistics | 2021 |
| Neil MAC Golf Ltd | Arts & recreation | 2024 |
| NEO Brothers Limited | Wholesale & retail | 1995 |
| Neo-Cass Holdings Ltd | Financial services | 2015 |
| Neohype Limited | Professional & scientific | 2017 |
| Never Forget Your Roots Ltd | Other services | 2025 |
| Nevz Kitchen Limited | Hospitality | 2019 |
| New Edge Investments Limited | Information & communication | 2016 |
| New Hudson Heritage Ltd | Manufacturing | 2026 |
| New Oriental Exress Ltd | Hospitality | 2023 |
| New World Recruitment Limited | Administrative & support | 2017 |
| Nexgen Consultancy Ltd | Administrative & support | 2024 |
| Nexus Construction Consulting Ltd | Construction | 2025 |
| Nexus Plumbing and Heating Ltd | Construction | 2017 |
| Nice N' Spiky Comedy Limited | Arts & recreation | 2017 |
| Nicomatic (UK) Ltd | Wholesale & retail | 1996 |
| NINE-19 Media Ltd | Information & communication | 2012 |
| NJA Accountancy Ltd | Professional & scientific | 2022 |
| Nkay Healthcare Solutions Limited | Health & social care | 2019 |
| NO Payne NO Gain Limited | Information & communication | 2014 |
| NO Trace Ltd | Arts & recreation | 2018 |
| Node IT Solutions Limited | Information & communication | 2008 |
| Nonno Joe's Restaurants Biggleswade Limited | Hospitality | 2018 |
| Nonno Joes Limited | Hospitality | 2013 |
| Norfolk Estates Ltd | Real estate | 2024 |
| North Herts Chiropody Limited | Health & social care | 2011 |
| North West London Couriers Limited | Transport & logistics | 1997 |
| NORTH19 Productions Limited | Information & communication | 2014 |
| Northcott Data Limited | Wholesale & retail | 1999 |
| November Media Limited | Information & communication | 2018 |
| NP Hygiene & Aesthetics Limited | Health & social care | 2021 |
| NSD Potatoes Ltd | Agriculture & fishing | 2008 |
| NUK Electronics Limited | Professional & scientific | 2006 |
| Number 1 London Road Ltd | Extraterritorial | 2025 |
| Nuxies Ltd | Hospitality | 2026 |
| NWR Talent Ltd | Education | 2025 |
| NX Lifestyle Logistics UK Ltd | Transport & logistics | 2002 |
| Nymeria Networks Limited | Information & communication | 2020 |
| Oak Lodge Properties Limited | Real estate | 1993 |
| Oak Street Logistics Ltd | Wholesale & retail | 2011 |
| Oakland Blinds Limited | Wholesale & retail | 2007 |
| OCD FM Ltd | Construction | 2014 |
| OG Productions Ltd | Information & communication | 2014 |
| Ojala Limited | Information & communication | 2013 |
| Okley Management Ltd | Arts & recreation | 2023 |
| Old Town Plumbing & Heating Ltd | Construction | 2024 |
| Old Warden Limited | Manufacturing | 2007 |
| On-Call Group Limited | Administrative & support | 2015 |
| On-Pole Limited | Professional & scientific | 2006 |
| One Take Voices Ltd | Arts & recreation | 2019 |
| Onyx Chocolate Productions Ltd | Arts & recreation | 2026 |
| Onyx FX Limited | Information & communication | 2024 |
| Onyx Management Accounting Ltd | Professional & scientific | 2011 |
| Oracle Electrical Installation Ltd | Construction | 2012 |
| Oracle Social Care Limited | Health & social care | 2016 |
| Orange Building Solutions Limited | Construction | 2014 |
| Orange Decorating Services Limited | Construction | 2019 |
| Orangemont Limited | Information & communication | 2021 |
| Orchid Blue Ltd | Information & communication | 2016 |
| Original Solutions Limited | Professional & scientific | 2021 |
| Original Spin Designs Limited | Administrative & support | 2012 |
| Original Spin Gifts Ltd | Administrative & support | 2023 |
| Oscars Emporium Ltd | Wholesale & retail | 2023 |
| Otterhead Limited | Information & communication | 2011 |
| Outsourced IT Limited | Information & communication | 2006 |
| Overcomer Family Church Ltd | Other services | 2008 |
| Oxhey Hall Consulting Ltd | Professional & scientific | 2012 |
| OZ Electrics Ltd | Construction | 2023 |
| P and H Equestrian (Livery) Ltd | Arts & recreation | 2025 |
| P&P Leisure Pools Limited | Construction | 2021 |
| P. Allen Services Limited | Agriculture & fishing | 2006 |
| Pablo Mendelssohn Music Ltd | Arts & recreation | 2022 |
| PAF Excellence Ltd | Hospitality | 2021 |