| MPA Legal Services Ltd | Professional & scientific | 2021 |
| MPA Professional Services LLP | | 2023 |
| MR Clean Drycleaners Ltd | Other services | 2020 |
| MR Van (MK) Ltd | Wholesale & retail | 2018 |
| Mucky Ducks Management Ltd | Health & social care | 2023 |
| MUM to MUM Limited | Manufacturing | 2018 |
| Mumpod Company Limited | Manufacturing | 2021 |
| Murphy Inoue Ltd | Real estate | 2017 |
| Mursley Free Range EGG Supplies Limited | Wholesale & retail | 2013 |
| Muscat Roberts Ltd | Real estate | 2024 |
| Music Go Round Ltd | Administrative & support | 2009 |
| My Nhfs Limited | Financial services | 2014 |
| MZ Machinery Services Limited | Manufacturing | 2011 |
| N a Interiors Limited | Construction | 2008 |
| N and B Property Holdings Ltd | Real estate | 2018 |
| Nagram.Net Ltd | Information & communication | 2024 |
| Nails and Beauty MK Ltd | Other services | 2022 |
| National Sound Ltd | Information & communication | 2023 |
| Navaura Concierge Ltd | Wholesale & retail | 2025 |
| NB Property Group Holdings Ltd | Financial services | 2017 |
| NB Property Holdings 119 High ST Ltd | Real estate | 2017 |
| NB Property Renovations Ltd | Construction | 2017 |
| NB Property Solutions Ltd | Real estate | 2014 |
| NB Residential Holdings Ltd | Real estate | 2022 |
| Nene Valley Paving Ltd | Wholesale & retail | 2007 |
| Nentex Limited | Wholesale & retail | 2024 |
| Neonpeak Digital Solutions Ltd | Information & communication | 2025 |
| Nestrixliving Ltd | Real estate | 2026 |
| Network Video Solutions Limited | Professional & scientific | 2002 |
| Nevaeh IT Limited | Information & communication | 2018 |
| Neville Blackwood Ltd | Public administration | 2011 |
| New Housing Solutions Limited | Professional & scientific | 2024 |
| New Skin Beauty Therapy Ltd | Wholesale & retail | 2025 |
| Newport Autoz Ltd | Wholesale & retail | 2021 |
| Newport CNC Limited | Manufacturing | 2010 |
| Newport Curry Ltd | Hospitality | 2023 |
| Newport DG Limited | Hospitality | 2015 |
| Newport Kebab Limited | Hospitality | 2015 |
| Newport Music Limited | Wholesale & retail | 2014 |
| Newport News Ltd | Wholesale & retail | 2020 |
| Newport Pagnell Automation Limited | Information & communication | 2021 |
| Newport Pagnell Baptist Church Development Ltd | Construction | 2019 |
| Newport Pagnell Bowling Club,Limited | Arts & recreation | 1944 |
| Newport Pagnell Consulting Limited | Professional & scientific | 2019 |
| Newport Spice Limited | Hospitality | 2025 |
| Nexgenix Technologies Ltd | Information & communication | 2026 |
| NG Space Engineering Limited | Information & communication | 2008 |
| Nick Cook Retail and Leisure Ltd | Real estate | 2020 |
| Nick O'Connor Copywriting Ltd | Information & communication | 2019 |
| Nigel Michael COX Ltd | Extraterritorial | 2024 |
| Nigel Willard Limited | Arts & recreation | 2011 |
| NINETEEN96 Limited | Real estate | 2018 |
| Nipton Publishing Limited | Extraterritorial | 2008 |
| NJR Accommodation Ltd | Real estate | 2019 |
| Noble Investment Group Limited | Real estate | 2024 |
| Noble Romans Limited | Hospitality | 1981 |
| North Bucks Machining Limited | Professional & scientific | 2009 |
| Northwood MK Limited | Real estate | 2000 |
| Novaira Insights Ltd | Professional & scientific | 2021 |
| NP Aesthetics Ltd | Health & social care | 2022 |
| NP PJ Pizza Limited | Hospitality | 2020 |
| NPR Recruit Limited | Administrative & support | 2010 |
| NPS Electrical Services Ltd | Construction | 2016 |
| Nreel Ltd | Real estate | 2024 |
| Nthanda Care Ltd | Health & social care | 2022 |
| Nunc Limited | Extraterritorial | 2010 |
| Nureta Ltd | Wholesale & retail | 2023 |
| Nutriscape Ltd | Professional & scientific | 2024 |
| O & M Contracting Ltd | Administrative & support | 2015 |
| O - Frontier Tech (UK) Limited | Financial services | 2025 |
| O - Human Resources (UK) Ltd | Financial services | 2024 |
| O'Hanlon & Sons Limited | Construction | 1998 |
| Oak Tree Building Solutions Ltd | Construction | 2022 |
| Oaklen Construction Ltd | Construction | 2025 |
| Oakley Lorien Limited | Real estate | 2011 |
| Oakley Trio Limited | Real estate | 2020 |
| Oakshire Group Ltd | Administrative & support | 2026 |
| Oakstone Living Ltd | Real estate | 2026 |
| OC Cleaning Services Ltd | Administrative & support | 2019 |
| Occasion Queens Limited | Information & communication | 2016 |
| Octagon Commercial Finance Ltd | Financial services | 2022 |
| Octagon Financial Advice Ltd | Financial services | 2020 |
| Octopus Restaurant Consulting Limited | Professional & scientific | 2020 |
| Odds on Music Publishing Limited | Manufacturing | 1992 |
| Odell Investments Limited | Real estate | 2015 |
| OED Trading Ltd | Wholesale & retail | 2025 |
| Office Furniture Requirements Limited | Wholesale & retail | 1998 |
| Oggie's Bikes Ltd | Other services | 2012 |
| Ohmio UK Ltd | Information & communication | 2022 |
| OHS4U Ltd | Extraterritorial | 2019 |
| Oiyaa Local Limited | Administrative & support | 2020 |
| Old Dowmans Farm Ltd | Households | 2021 |
| Old Rectory Close Ltd | Households | 2014 |
| Old Town Hall Chambers Management Limited | Administrative & support | 2015 |
| Oleoleg Ltd | Transport & logistics | 2021 |
| Olive Proofreading and Editing Limited | Information & communication | 2024 |
| Ollerhead Consulting Limited | Professional & scientific | 2025 |
| OLY Care Limited | Information & communication | 2025 |
| Oncilla Security Ltd | Administrative & support | 2024 |
| One Link Services Ltd | Information & communication | 2025 |