| Albourne Enterprises Limited | Professional & scientific | 1997 |
| Aldo Investments Limited | Construction | 1964 |
| Alermay Flat Management Limited | Professional & scientific | 1993 |
| Alertapack Ltd | Administrative & support | 2019 |
| Alexandra & Leopold Limited | Real estate | 2003 |
| Alfa Dental Limited | Health & social care | 2007 |
| Alice Tierney Limited | Education | 2005 |
| Allevent Radio Services Limited | Manufacturing | 2004 |
| Alliam Limited | Construction | 2016 |
| Allied Building Products Ltd. | | 1989 |
| Allied Factors Limited | Information & communication | 1989 |
| Allimax International Limited | Wholesale & retail | 2000 |
| Allseasons Landscaping & Design LLP | | 2007 |
| Allsorts Youth Project Ltd | Health & social care | 2001 |
| Alpha Endeavours Limited | Other services | 1989 |
| Altered Images Picture Framing Limited | Wholesale & retail | 2003 |
| Amala Vegan Ltd | Wholesale & retail | 2014 |
| Amaze Brighton and Hove | Information & communication | 1999 |
| Ambassador Company (Hastings) Limited(The) | Real estate | 1962 |
| Ambrafund Advisers Limited | Professional & scientific | 2000 |
| Amsafons Ltd | Financial services | 2025 |
| Amsland Limited | Professional & scientific | 1989 |
| Amstech Group (UK) Limited | Financial services | 2006 |
| ANA Investments Limited | Financial services | 2002 |
| ANA Williams Limited | Professional & scientific | 2018 |
| Anderida (Therapy) Limited | Health & social care | 2004 |
| Andrew Parr Ltd | Other services | 2004 |
| Andrew Pridell Associates Limited | Professional & scientific | 2005 |
| Andrew Sykes Micro-Electronics Consultants Limited | Professional & scientific | 1986 |
| Andrew Wood Limited | Administrative & support | 2003 |
| Andrews Accountancy Services Limited | Professional & scientific | 2004 |
| Andy Wilkes Training & Consultancy Limited | Administrative & support | 2010 |
| Anglesea Residents Company Limited | Real estate | 1999 |
| Anglo Continental Placements Limited | Administrative & support | 2002 |
| Anglofile International Limited | Information & communication | 1995 |
| ANJ Homes Ltd | Real estate | 2023 |
| ANN Barnard Limited | Arts & recreation | 2002 |
| Anthony Michael Limited | Other services | 1997 |
| Antix Software Limited | Information & communication | 1998 |
| Antwords Limited | Other services | 2001 |
| APA Airline Management Limited | Transport & logistics | 2007 |
| Apex Football Group Limited | Arts & recreation | 2022 |
| Apex Personnel Limited | Administrative & support | 2003 |
| APG Solutions Emea Limited | Manufacturing | 2004 |
| Apollo Printers Limited | Manufacturing | 2007 |
| Applecroft Consultants Ltd | Information & communication | 2002 |
| Applehill Limited | Real estate | 2003 |
| Appsys Ltd | Information & communication | 2008 |
| AQT Global Ltd | Administrative & support | 2007 |
| Aqua Leader Ltd | Administrative & support | 2004 |
| ARC Engineering Fabrication Limited | Manufacturing | 1998 |
| Arcarius Ltd | Professional & scientific | 2002 |
| Archers of Westfield Limited | Wholesale & retail | 2005 |
| Archery Gardens Management Limited | Households | 2019 |
| ARK1 Limited | Manufacturing | 2007 |
| Arlis Consulting Limited | Administrative & support | 2005 |
| Art Producing Economic Community | Arts & recreation | 2003 |
| Artemis Childcare Limited | Health & social care | 2006 |
| Artful Octopus Ltd | Wholesale & retail | 2023 |
| Arthur C. Towner Limited | Other services | 1938 |
| Arun Furnishers Limited | Wholesale & retail | 2003 |
| Arundel Place Limited | Real estate | 2003 |
| Ascham Residents Association Limited | Households | 1979 |
| ASH DIE Back Limited | Administrative & support | 2007 |
| ASH Tree Accounting Limited | Professional & scientific | 2002 |
| Ashburnham Christian Trust | Hospitality | 1960 |
| Ashbury Loft Conversions Limited | Wholesale & retail | 2004 |
| Ashdown Estate Management (Bexhill) Limited | Households | 1994 |
| Ashdown Phillips & Partners Limited | Real estate | 2004 |
| Ashdown Phillips & Partners Resources Limited | Real estate | 2004 |
| Ashdown Real Estate Ltd | Real estate | 2020 |
| Ashdown Site Investigation Limited | Administrative & support | 1989 |
| Ashendens Ltd | Administrative & support | 2003 |
| Ashford Self Storage Limited | Transport & logistics | 2000 |
| Ashley Developments Limited | Construction | 2006 |
| Ashley Gardens Resource Centre Limited | Real estate | 1994 |
| Ashley Gardens(Uk) Ltd | Health & social care | 2005 |
| Ashmit Properties Limited | Professional & scientific | 2004 |
| Ashton Lodge (Sunbury) Ltd | Administrative & support | 2005 |
| Aspects Beauty Company Limited | Wholesale & retail | 1993 |
| Aspen Pumps Group Limited | Administrative & support | 2007 |
| Assassins Gym Ltd | Arts & recreation | 2013 |
| Associated Trade & Technology Limited | Arts & recreation | 1990 |
| Aston Peel Limited | Administrative & support | 2000 |
| Atlas Travel Private Hire Limited | Transport & logistics | 2005 |
| Austin Rees Limited | Real estate | 1995 |
| Autokit Accessories Ltd | Wholesale & retail | 2006 |
| Avilfarm Investments Limited | Real estate | 1958 |
| Avloc Services Limited | Professional & scientific | 2002 |
| AVT Connect Ltd. | Information & communication | 1993 |
| Axel Direct Limited | Construction | 2003 |
| Axis Construction Ltd | Administrative & support | 2005 |
| Axle Publishing Limited | Information & communication | 1998 |
| Aylesbury Properties Limited | Households | 1987 |
| B a S (School) Limited | Education | 1963 |
| B Enterprises Ltd | Wholesale & retail | 2017 |
| B J Wood and SON Limited | Manufacturing | 2007 |
| B W Associates (Sussex) Limited | Professional & scientific | 2003 |
| B.C.N.S Limited | Real estate | 2001 |
| Back to Health Clinics Limited | Health & social care | 2002 |