| Millmead Limited | Construction | 2003 |
| MINIMUMCO2 Ltd | Professional & scientific | 2012 |
| MJP Roofing & Construction Limited | Construction | 2021 |
| Mortimers (Prestige) Ltd | Wholesale & retail | 2018 |
| MOT & Service Centre Wisborough Green Limited | Wholesale & retail | 2018 |
| Msteamstelephony Ltd | Information & communication | 2021 |
| MTA Solutions Limited | Extraterritorial | 2006 |
| Muddy PAW Prints Ltd | Professional & scientific | 2023 |
| Mulberry Projects Limited | Agriculture & fishing | 2004 |
| Mv&J Ltd | Hospitality | 2024 |
| My First Wheels Ltd | Wholesale & retail | 2022 |
| My Suite Home Ltd | Wholesale & retail | 2025 |
| Mydas Estates Ltd | Real estate | 2024 |
| Mythron Cars Ltd | Wholesale & retail | 2024 |
| Mzondi Investments Limited | Real estate | 2002 |
| N & J Murphy Limited | Health & social care | 2015 |
| N.H. Etheridge (Building) Limited | Construction | 1978 |
| N.P.Stanley Limited | Construction | 2011 |
| Natively Digital Limited | Information & communication | 2013 |
| NET Zero Networking Limited | Administrative & support | 2022 |
| Network Next Generation Ltd | Administrative & support | 2025 |
| Networked People Limited | Professional & scientific | 2020 |
| New Avenue Projects Limited | Financial services | 2004 |
| New World Wind Limited | Energy | 2018 |
| Newington Bricks Limited | Extraterritorial | 1906 |
| Newpound Car Wash Ltd | Wholesale & retail | 2019 |
| Newpound Spray Shop Limited | Construction | 2019 |
| Newstead Hall Management Company Limited | Households | 2001 |
| Nexus(Tm) Ltd | Construction | 2022 |
| Nicholas Charles Group Limited | Extraterritorial | 2017 |
| Nicholls Boreholes and Ground Source Limited | Households | 2024 |
| Nicholls Countryside Construction Limited | Construction | 2002 |
| Nicholls Developments Limited | Construction | 2013 |
| Nicholls Licensing Limited | Construction | 2022 |
| Nicholls Water Credits Limited | Households | 2024 |
| Niscor Limited | Other services | 2021 |
| NK Admin Ltd | Administrative & support | 2026 |
| Noosa Limited | Other services | 2015 |
| NOT Equal to Ltd | Information & communication | 2025 |
| NSB Property Investment Limited | Real estate | 2022 |
| Nubi Marketing Ltd | Professional & scientific | 2018 |
| Nubi Studios Ltd | Professional & scientific | 2020 |
| Nyewood Brick Company Limited | Professional & scientific | 1988 |
| O.B Fabrication Ltd | Manufacturing | 2024 |
| Oak Way Residents Association Limited | Households | 2006 |
| Oakhurst Developments Limited | Construction | 2026 |
| OC Catering Ltd | Hospitality | 2024 |
| OFF Grid Utility Services Ltd | Construction | 2020 |
| One EV Sussex Ltd | Wholesale & retail | 2025 |
| Oozio Ltd | Information & communication | 2015 |
| Orchard Construction & Project Management Limited | Administrative & support | 1997 |
| Ori-Inu Ltd | Information & communication | 2024 |
| Oriental Express Take Away Limited | Hospitality | 2016 |
| Osborne Carpentry & Construction Ltd | Manufacturing | 2021 |
| OSI Investments Limited | Other services | 1983 |
| Osmaston Farrant Agricultural Services Ltd | Agriculture & fishing | 2026 |
| Oxley Aston Co. Limited | Professional & scientific | 1959 |
| P B Overington Electrical Contractor Ltd | Construction | 2019 |
| P D Motors (Billingshurst) Ltd | Wholesale & retail | 2004 |
| P J Logistics Limited | Transport & logistics | 1998 |
| PAC Services Sussex LLP | | 2012 |
| Pacserv Ltd | Professional & scientific | 2020 |
| Pada Ventures Ltd | Professional & scientific | 2024 |
| Paddock Motor Racing Ltd | Arts & recreation | 2026 |
| Pakenham Education Limited | Wholesale & retail | 2015 |
| Pallet Truck Services (Sussex) Limited | Manufacturing | 2013 |
| Pane Free Window Cleaning Limited | Administrative & support | 2019 |
| Paragon Plating Limited | Manufacturing | 1989 |
| Parlour Nails & Spa Limited | Other services | 2025 |
| Pasivm Limited | Health & social care | 2021 |
| Paternosters Estates Limited | Professional & scientific | 1995 |
| Paternosters Property Nominees Limited | Professional & scientific | 2011 |
| PDM 68 Holdings Limited | Financial services | 2026 |
| Peard Limited | Professional & scientific | 2011 |
| Pegley Groundworks Limited | Construction | 2015 |
| Percybaxter Ltd | Professional & scientific | 2020 |
| Peter Gibson Associates Limited | Professional & scientific | 2008 |
| Petworth Park Cricket Club CIC | Arts & recreation | 2017 |
| Petworth Sessions CIC | Arts & recreation | 2024 |
| Pharmasupply Advisory Ltd | Professional & scientific | 2022 |
| Phillip Luff Associates Ltd | Information & communication | 2023 |
| Physio Refined Ltd | Health & social care | 2025 |
| Pink Diamond Travel Limited | Administrative & support | 2021 |
| Pipeline Plumbing Services Ltd | Construction | 2009 |
| Pizza & Chicken Planet Ltd | Hospitality | 2026 |
| Pizza Planet (Sussex) Ltd | Hospitality | 2018 |
| PJ Logistics (Europe) LLP | | 2011 |
| PJB Security Products Ltd | Extraterritorial | 2025 |
| PJT Flight Training Ltd | Education | 2018 |
| PJT Global Investments Ltd | Financial services | 2024 |
| Pkec Ltd | Real estate | 2026 |
| Plaistow Village Trust Limited | Other services | 2005 |
| Plane Aviation Ltd | Professional & scientific | 2026 |
| Plas Newydd Consulting Limited | Professional & scientific | 2012 |
| Platinum Roofing and Guttering Ltd | Extraterritorial | 2025 |
| Plumridge and Peters Limited | Manufacturing | 1976 |
| PN Communications Ltd | Information & communication | 2003 |
| POD Portfolio Ltd | Real estate | 2023 |
| POL Consultants Limited | Professional & scientific | 2021 |
| Polfire Ltd | Professional & scientific | 2024 |