| Mannix HR Limited | Administrative & support | 2021 |
| Marco Nardi Limited | Professional & scientific | 2005 |
| Marlborough Court Newhaven Limited | Real estate | 2004 |
| Marshall Plumbing & HTG Limited | Construction | 2026 |
| Martlew Garden Services Limited | Other services | 2005 |
| Martyn Smith Creative Ltd | Professional & scientific | 2015 |
| Mascol Productions Ltd | Information & communication | 1983 |
| Maverick DOE Hair Co Ltd | Wholesale & retail | 2021 |
| Mcginty Mining Limited | Construction | 2014 |
| Medasani Properties Limited | Real estate | 2021 |
| Medication Delivery Services Limited | Administrative & support | 2007 |
| Meghan Services Ltd | Professional & scientific | 2026 |
| Meridian Facilities Support Ltd | Administrative & support | 2015 |
| Meridian Motors Peacehaven Limited | Extraterritorial | 2014 |
| Merlin 2005 Ltd | Other services | 2022 |
| Microslat UK Limited | Extraterritorial | 2018 |
| Military Events Limited | Arts & recreation | 2015 |
| Military Odyssey Limited | Arts & recreation | 2000 |
| Military World Limited | Information & communication | 2022 |
| Millennium Carpentry Limited | Construction | 1998 |
| Mind Body Dog Training Limited | Professional & scientific | 2021 |
| Mind Your Head Removals Ltd | Transport & logistics | 2022 |
| Minnie & Missie's Helping Furry Paws Ltd | Other services | 2025 |
| Minnie & Missie's Helping Paws Limited | Other services | 2026 |
| MJ Realty Ltd | Real estate | 2020 |
| MJC Paddock Limited | Real estate | 2013 |
| ML Engineering and Supplies Ltd | Wholesale & retail | 2007 |
| Mmczubala Limited | Professional & scientific | 2016 |
| Moffett Electric Source Ltd | Construction | 2025 |
| Money Pipe Ltd. | Transport & logistics | 2009 |
| Monton Limited | Health & social care | 2025 |
| Moonlit Cart Ltd | Wholesale & retail | 2025 |
| Moose Fightwear Ltd | Manufacturing | 2025 |
| Mould Solutions Sussex Ltd | Construction | 2003 |
| Moved by Experts Limited | Transport & logistics | 2023 |
| Moxon Land and Developments Limited | Construction | 2026 |
| Mpma Limited | Other services | 1979 |
| MPV General Builder’S Ltd | Construction | 2022 |
| MR Tashman Ltd | Other services | 2017 |
| Mrsbuy Londn Ltd | Wholesale & retail | 2021 |
| Mstb Property Management Ltd | Construction | 2026 |
| My Neighbour's Shed Limited | Construction | 2026 |
| My Sherpa Ltd | Professional & scientific | 2025 |
| My Sherpa Programmes Ltd | Professional & scientific | 2020 |
| Myth Forged Ltd | Manufacturing | 2022 |
| N. Kerslake SON Limited | Extraterritorial | 2008 |
| Ncgln Limited | Public administration | 2021 |
| Neat Feet Limited | Health & social care | 1997 |
| Neith Executive Solutions Ltd | Administrative & support | 2025 |
| Nest Projects Group Ltd | Construction | 2026 |
| NET OPS Ltd | Information & communication | 2018 |
| New Croydon CIC | Health & social care | 2025 |
| New Legacy Media Ltd | Information & communication | 2025 |
| Nguyen Estates Limited | Real estate | 2019 |
| Nicholson Cleaning Limited | Other services | 2017 |
| Nickiodp Limited | Health & social care | 2024 |
| Nika Home Ltd | Wholesale & retail | 2023 |
| NO Time Zone Limited | Other services | 2020 |
| Nolitter.Uk Ltd | Professional & scientific | 2023 |
| Normeldo's Ltd | Health & social care | 2022 |
| North United Properties Limited | Real estate | 2025 |
| Nyala EVA Global Ltd | Administrative & support | 2025 |
| Oakwood Property and Developments Limited | Real estate | 2016 |
| Ocean Reach Residents Limited | Households | 2006 |
| Offen Landscape Construction Limited | Administrative & support | 2022 |
| Official Teetee Ltd | Wholesale & retail | 2025 |
| One Brown PAW Ltd | Information & communication | 2022 |
| One Crown Pensions Limited | Financial services | 2023 |
| Original V Productions Limited | Wholesale & retail | 2021 |
| Owenmedia Ltd | Information & communication | 2015 |
| P.W Holdings Ltd | Real estate | 2020 |
| Papachinos Limited | Hospitality | 2016 |
| Papachino’S Cafes Ltd | Hospitality | 2020 |
| Paragon Aegis Ltd | Health & social care | 2018 |
| Parkes Productions Limited | Information & communication | 2007 |
| Pawel Stepien Ltd | Administrative & support | 2012 |
| Pawztodoorz Fieldz Ltd | Other services | 2026 |
| PD Plastics Southern Ltd | Construction | 2018 |
| Peacehaven Electrical Ltd | Professional & scientific | 2026 |
| Peacehaven Electrical Services Limited | Construction | 2003 |
| Peacehaven Taxis Limited | Transport & logistics | 2011 |
| Philip Farrington Properties Limited | Real estate | 1965 |
| Phoenix Plus Limited | Real estate | 2019 |
| Pierre Dental Ltd | Health & social care | 2018 |
| Pink and Blue Hampers Ltd | Wholesale & retail | 2022 |
| Pink DOT Design Limited | Wholesale & retail | 2023 |
| Pink Peach Events Ltd | Health & social care | 2024 |
| PJ Properties South East Ltd | Real estate | 2024 |
| PJM Interiors Limited | Construction | 2009 |
| PK Barber Ltd | Other services | 2019 |
| Playbook Insight Limited | Information & communication | 2025 |
| PM Drainage Ltd | Water & waste | 2019 |
| Polished Beauty Sussex Ltd | Other services | 2025 |
| Poplett of Peacehaven Limited | Real estate | 1962 |
| Portalchemy Ltd | Information & communication | 2014 |
| Portway Games Limited | Extraterritorial | 2002 |
| Precision Cctv Ltd | Administrative & support | 2020 |
| Prismreach Limited | Professional & scientific | 2026 |
| PRK Surveying & Project Management Ltd | Construction | 2024 |
| Promenade Systems Ltd | Information & communication | 2013 |