| A. F. Payne Limited | Construction | 2011 |
| A. G. Resident Co. Limited | Real estate | 1972 |
| A.B.Heather.Carpentry & Joinery Ltd | Administrative & support | 2002 |
| A.D.Broughton Limited | Construction | 1968 |
| A.G.Beer Brickwork Ltd | Construction | 2020 |
| A.J. & M.R. Terry Limited | Construction | 2002 |
| A1 Compusolve Ltd | Information & communication | 2013 |
| AA Car Sales Ltd | Wholesale & retail | 2017 |
| Aabl Ltd | Transport & logistics | 2025 |
| Aacr (Refrigeration & Air Conditioning) Ltd | Manufacturing | 2015 |
| Aasser Ltd | Transport & logistics | 2021 |
| Abaculus Limited | Real estate | 2016 |
| Abacus Lettings (Sussex) Ltd | Administrative & support | 2005 |
| Abbey Scaffolding (Sussex) Limited | Construction | 2008 |
| Abbotswood Limited | Real estate | 1989 |
| ABC Elevators Limited | Professional & scientific | 2018 |
| Abid Jaffer Holdings Ltd | Financial services | 2025 |
| Above ALL Roofing & Building Specialists Ltd | Construction | 2009 |
| ABR Environment Limited | Water & waste | 2022 |
| Absolute Electrical Southern LLP | | 2016 |
| Absolute-Heat Ltd | Construction | 2020 |
| Ac&C Enterprises Limited | Real estate | 2025 |
| Ac-Manufacturing Ltd | Manufacturing | 2022 |
| Academy Group Limited | Professional & scientific | 1990 |
| Access-Uk Limited | Construction | 2014 |
| Accounting Extra Limited | Professional & scientific | 2012 |
| Accounting Figures Limited | Professional & scientific | 2009 |
| Accuracy Office Solutions Limited | Manufacturing | 2012 |
| Ace Building Services (Southern) Ltd | Construction | 2014 |
| Ace Removals & Logistics Limited | Transport & logistics | 2023 |
| ACL Mobile Homes Limited | Hospitality | 2016 |
| Acorn Mews (Denmead) Management Limited | Households | 2009 |
| Across the World Limited | Extraterritorial | 2006 |
| Acsim Group Ltd | Energy | 2016 |
| Action X Ltd | Extraterritorial | 2022 |
| Activestyles Ltd | Wholesale & retail | 2026 |
| Activise Ltd | Arts & recreation | 2006 |
| Actuated Solutions Limited | Manufacturing | 2003 |
| AD Select Autos Limited | Wholesale & retail | 2025 |
| Adam Cunard Ltd | Education | 2018 |
| Adames (Flansham) Limited | Agriculture & fishing | 1965 |
| Adams Beeny Limited | Professional & scientific | 2006 |
| Adaptmoney Limited | Professional & scientific | 1996 |
| Adele Peters Performing Arts School Limited | Arts & recreation | 2015 |
| ADL Care Limited | Other services | 2020 |
| Adorn ME Ltd | Professional & scientific | 2011 |
| Advance Property Services London Limited | Construction | 2016 |
| Advanced PT UK Limited | Education | 2024 |
| Adzzzy's Armoury Ltd | Manufacturing | 2025 |
| Aegis Consultancy Services Limited | Health & social care | 2004 |
| AEK Accountancy Ltd | Professional & scientific | 2025 |
| AEK Holdings Ltd | Financial services | 2025 |
| Aforce Pest Control Limited | Administrative & support | 2015 |
| AG Electrical (South) Ltd | Construction | 2026 |
| AG Escargot Limited | Agriculture & fishing | 2018 |
| AG Products Ltd | Wholesale & retail | 2018 |
| Agalettings Limited | Real estate | 2026 |
| Agent Labour Ltd | Extraterritorial | 2024 |
| AHK Engineering Limited | Professional & scientific | 2015 |
| AI Build Software Limited | Information & communication | 2026 |
| Aircraft Certification Services Limited | Administrative & support | 1979 |
| Airside Labs Ltd | Information & communication | 2025 |
| Airstream Leisure Limited | Other services | 1999 |
| AJ Singh UK Limited | Wholesale & retail | 2013 |
| AJM Home Help Ltd | Health & social care | 2022 |
| AJM Sussex Properties Ltd | Real estate | 2025 |
| AJP Property Development Ltd | Real estate | 2025 |
| AK Property & Construction Services Ltd | Construction | 2025 |
| Alan Sullivan Consultancy Services (Ascs) Ltd | Professional & scientific | 2019 |
| Alchemy Design Group Limited | Wholesale & retail | 2016 |
| Aldingbourne House Management Company Limited | Households | 1993 |
| Aldwick Bay Company Limited | Households | 1988 |
| Aldwick Bay Management Limited | Real estate | 1974 |
| Aldwick Builders Ltd | Manufacturing | 2019 |
| Aldwick Cafe Ltd | Hospitality | 2025 |
| Aldwick GAS Limited | Construction | 2025 |
| Aldwick Grange Residents' Association Limited | Households | 1976 |
| Aldwick Hotel LLP | | 2007 |
| Aldwick Indian Takeaway Ltd | Hospitality | 2022 |
| Aldwick Landscapes Limited | Administrative & support | 2015 |
| Aldwick PUB Company Limited | Hospitality | 2022 |
| Alecsflo Ltd | Wholesale & retail | 2026 |
| Alfred Jackson Ltd | Wholesale & retail | 2025 |
| ALI & Jaffer Holdings Ltd | Financial services | 2025 |
| Aliaura Management Company Limited | Households | 2017 |
| Aljo Ents Limited | Arts & recreation | 2013 |
| ALL Cleared Solutions Ltd | Information & communication | 2025 |
| ALL Heights Roofing Ltd | Construction | 2025 |
| ALL Heights Roofing Services Limited | Construction | 2015 |
| ALL Rise Workshops Limited | Professional & scientific | 2026 |
| Allarton Ltd | Arts & recreation | 2016 |
| Allbright Holdings Limited | Financial services | 2025 |
| Allbright Limited | Construction | 2019 |
| Allbright Windows & Doors Sussex Limited | Manufacturing | 2025 |
| Allenby House Investments Ltd | Construction | 1999 |
| Allgood Cleaning Services Limited | Other services | 2003 |
| Allsorts Airsoft Limited | Wholesale & retail | 2018 |
| Almea Electrical Limited | Construction | 2020 |
| Almodington Nurseries Limited | Agriculture & fishing | 1983 |
| Alpha Court Residents' Association Limited | Real estate | 1982 |