| MR JAM Media Ltd | Information & communication | 2020 |
| MR London Limited | Professional & scientific | 2019 |
| MR MOT Ltd | Wholesale & retail | 2013 |
| MR MOW Ltd | Professional & scientific | 2025 |
| MRK Specialist Roofing Limited | Construction | 2024 |
| MSM Transform Ltd | Information & communication | 2016 |
| MUD HUT Records Limited | Administrative & support | 1998 |
| Mullbiologics Consultancy Ltd | Professional & scientific | 2012 |
| Mura -Clearance Ltd | Water & waste | 2022 |
| Musana Home Care Services Limited | Health & social care | 2025 |
| Music Producers Guild Awards Limited | Professional & scientific | 2013 |
| Mutual Ideas Limited | Professional & scientific | 1999 |
| MVG Films Limited | Information & communication | 2019 |
| MW Eflow Ltd | Hospitality | 2025 |
| MW Turfcare Ltd | Agriculture & fishing | 2024 |
| My Locksmith Solutions Ltd | Construction | 2015 |
| My Organic Lifestyle Ltd | Information & communication | 2025 |
| My Worthing Electrician Ltd | Energy | 2016 |
| Myrtle Stables Limited | Agriculture & fishing | 2022 |
| N J Wilson Ltd | Information & communication | 2023 |
| Nafeesa Ltd | Hospitality | 2019 |
| Naiad Plastics Limited | Manufacturing | 1975 |
| Naked Shelf Limited | Wholesale & retail | 2025 |
| Nash Care Solutions Ltd | Health & social care | 2018 |
| Nathan Abbott Consulting Ltd | Professional & scientific | 2022 |
| Nautilus Global Limited | Professional & scientific | 2019 |
| Navitech Limited | Wholesale & retail | 2010 |
| Navyblur Limited | Professional & scientific | 2009 |
| Naxco Services Ltd | Construction | 2020 |
| NAZ CGM Ltd | Construction | 2025 |
| NBT Property Limited | Real estate | 2021 |
| Neetrio DEV Ltd | Information & communication | 2021 |
| Neetrio Limited | Information & communication | 2021 |
| Neil Harman Optidress Services Limited | Other services | 2010 |
| NEO South Ltd | Hospitality | 2024 |
| Nepcote CMS Ltd | Information & communication | 2021 |
| Ness Associates Ltd | Administrative & support | 2010 |
| New Image Commercials Limited | Wholesale & retail | 2004 |
| New Life Computing Ltd | Other services | 2021 |
| New Moon Homes Limited | Real estate | 2018 |
| New South Law Limited | Professional & scientific | 2017 |
| New Tandoori Nights Ltd | Hospitality | 2023 |
| New Venture Care Ltd | Hospitality | 2019 |
| Newick Hill Residents Management Company Limited | Households | 2016 |
| News Plus (Angmering) Limited | Wholesale & retail | 2010 |
| Nextgen Vend Limited | Wholesale & retail | 2026 |
| Nfsp Ltd | Professional & scientific | 2014 |
| NGM Consult Limited | Professional & scientific | 2012 |
| NH Audio Design Ltd | Professional & scientific | 2023 |
| Nice AYE Ltd | Arts & recreation | 2015 |
| Nileroad Limited | Hospitality | 2019 |
| Ninety Nine Priory Road (Hastings Freeholders) Limited | Real estate | 2012 |
| Nineveh Shipyard Management Limited | Households | 1996 |
| NO BAD Fridays Ltd | Arts & recreation | 2021 |
| NO BAD Fridays Records Ltd | Wholesale & retail | 2024 |
| NO. 109 the Wellness Clinic Ltd | Health & social care | 2022 |
| NO. 109 the Wellness Consulting Rooms Ltd | Real estate | 2022 |
| Nobby & George Limited | Professional & scientific | 2014 |
| Noemi Blager Ltd | Professional & scientific | 2009 |
| Norfolk Gardens (East) Residents Association Limited | Administrative & support | 1996 |
| Norfolk Gardens West Residents Association Limited | Households | 2005 |
| Norfolk Road Residents Ltd | Households | 2015 |
| Norfolk Street Dental Surgery Limited | Health & social care | 2010 |
| Northern Squared Limited | Real estate | 2017 |
| Norton GMP Limited | Professional & scientific | 2025 |
| Notsa Technologies Limited | Professional & scientific | 2025 |
| Novaro Projects Ltd | Professional & scientific | 2025 |
| Novium Travel Limited | Professional & scientific | 2023 |
| Nrgpaths Advisory Ltd | Information & communication | 2026 |
| NTM Capital Holdings Ltd | Financial services | 2025 |
| Nufunc Ltd | Information & communication | 2017 |
| Number 2 Ltd | Information & communication | 2023 |
| Number 5 Fitzalan Road (Management Company) Limited | Households | 2006 |
| Nutes Design Limited | Other services | 2010 |
| Nyangai Ltd | Professional & scientific | 2014 |
| Nyetimber Management Ltd | Administrative & support | 2017 |
| Oaktree Apartments Management Company Limited | Households | 2021 |
| OBM Plumbing and Heating Limited | Construction | 2023 |
| Ockenden Manor Limited | Hospitality | 1985 |
| Octopus Accounting Solutions Limited | Professional & scientific | 2002 |
| ODT Group Ltd | Manufacturing | 2025 |
| OFF Plan Kitchens Limited | Manufacturing | 2013 |
| OFF Plan Property Developments Limited | Construction | 2024 |
| Officially Organic Ltd | Wholesale & retail | 2021 |
| Offset Entertainment Limited | Arts & recreation | 2025 |
| Ofmar Ltd | Information & communication | 2016 |
| OHH My Graze Limited | Hospitality | 2024 |
| OJS Diagnostic Ltd | Health & social care | 2017 |
| Olca Company Ltd | Construction | 2024 |
| Old Mill Court Worthing Limited | Households | 2010 |
| Old Warehouse Mews Management Company Limited | Households | 2001 |
| Olisex Developments Limited | Real estate | 2001 |
| Olly Martin Limited | Administrative & support | 2003 |
| Omega Control Solutions Holdings Limited | Manufacturing | 2025 |
| Omega Control Solutions Limited | Manufacturing | 2006 |
| ON the Button Ltd | Other services | 2020 |
| Onebin Ltd | Extraterritorial | 2018 |
| Ontrack (GB) Ltd | Administrative & support | 2011 |
| Open Flow Ltd | Administrative & support | 2021 |
| OPM Limited | Real estate | 2007 |