| Arkham Performance Limited | Wholesale & retail | 2013 |
| Arkmedes Limited | Information & communication | 2020 |
| ARL Investments Limited | Real estate | 2015 |
| Arlington Aesthetics Limited | Health & social care | 2022 |
| Arlington Cattery Ltd | Other services | 2010 |
| Arlington Road Medical LLP | | 2012 |
| Arlington Road Medical Services Limited | Health & social care | 2024 |
| Arlo & Sage Grooming Ltd | Other services | 2025 |
| Armour Property Guards Limited | Administrative & support | 2013 |
| Armoury Locks & Alarms Limited | Public administration | 2005 |
| Armstrong Fortescue Ltd | Other services | 2017 |
| Arnott GUY & Co Ltd | Financial services | 2004 |
| Arnworth Court (Eastbourne) Management Company Limited | Households | 2016 |
| Arohan Limited | Health & social care | 2022 |
| Around Education Psychology Consultancy Service Limited | Education | 2018 |
| Arrowstream Analytics Limited | Professional & scientific | 2021 |
| Art Buro Ltd | Administrative & support | 2013 |
| Art History in Focus Limited | Arts & recreation | 2013 |
| Artelmina Studio Ltd | Wholesale & retail | 2023 |
| Artemis Brighton Ltd | Administrative & support | 2016 |
| Artemis Internet Marketing Ltd | Information & communication | 2004 |
| Artemis Marketing Trustees Limited | Professional & scientific | 2025 |
| Arthritis Action | Health & social care | 1985 |
| Artisan Hair House Ltd | Other services | 2014 |
| Artizan-Coffee Ltd | Administrative & support | 2019 |
| Arun Lodge (Freehold) Ltd | Households | 2001 |
| Arundel Close Management Company Limited(The) | Households | 1979 |
| Arundel Keep (Eastbourne) Residents' Association Limited | Households | 1971 |
| Arundel RTM Company Limited | Households | 2018 |
| AS 1 - Activities Support One Ltd | Professional & scientific | 2019 |
| AS Breakfast Ltd | Hospitality | 2024 |
| AS Clean AS a Whistle Ltd | Administrative & support | 2026 |
| AS Electrical (Sussex) Limited | Construction | 2006 |
| AS Property Maintenance South Ltd | Construction | 2015 |
| Asad ALI Bakery Ltd | Hospitality | 2026 |
| Asak Tradings Limited | Wholesale & retail | 2025 |
| Asal Zakeri Limited | Health & social care | 2025 |
| Ascot Southern Limited | Real estate | 1987 |
| Asetiq Ltd | Professional & scientific | 2024 |
| Asfp Developments Limited | Extraterritorial | 2021 |
| Asgard Capital Partners Ltd | Financial services | 2015 |
| Asgard Labs Limited | Financial services | 2015 |
| ASH Sullivan Logistics Ltd | Transport & logistics | 2020 |
| ASH Towner Limited | Administrative & support | 1989 |
| Asha & Avni Ltd | Health & social care | 2022 |
| Ashbourne Court (Eastbourne) Limited | Households | 1995 |
| Ashcroft Consulting Limited | Professional & scientific | 2008 |
| Ashdown Building Company Limited | Construction | 2012 |
| Ashdown Gaming Limited | Wholesale & retail | 2020 |
| Ashdown Personnel Limited | Administrative & support | 2006 |
| Ashdown Plumbing & Heating Limited | Construction | 2002 |
| Ashdown Property Management Limited | Households | 2025 |
| Ashdown PUB Company Limited | Hospitality | 2016 |
| Ashford Construction Ltd | Construction | 2016 |
| Ashley S. Lupin & Associates Limited | Health & social care | 2006 |
| Ashley SIM Dentistry Limited | Health & social care | 2022 |
| Ashli Consulting Limited | Wholesale & retail | 2013 |
| Ashmit Holdings Limited | Financial services | 2017 |
| Ashton Digital Limited | Information & communication | 2026 |
| Ashton Fire Ltd | Professional & scientific | 2019 |
| Ashton Flow Limited | Professional & scientific | 2026 |
| Asia.Gaw Limited | Households | 2024 |
| Asian Food Eastbourne Ltd | Hospitality | 2026 |
| ASK Southern Contractors Ltd | Construction | 2023 |
| ASK Your Dentist Ltd | Information & communication | 2024 |
| Askcan Limited | Wholesale & retail | 2024 |
| Askews and Holts Library Services Ltd. | Wholesale & retail | 1992 |
| Aslap Limited | Construction | 1988 |
| Aslaq Ltd | Construction | 2025 |
| Asletts Development Ltd | Financial services | 2025 |
| Asljc Ltd | Real estate | 2020 |
| Asmel Limited | Wholesale & retail | 2025 |
| Aspect Metalcraft Ltd | Manufacturing | 2002 |
| Aspects Beauty Group Limited | Financial services | 2019 |
| Aspen Dental Care Ltd. | Health & social care | 2015 |
| Aspiration Homes LLP | | 2017 |
| Aspiration Tuition LLP | | 2026 |
| Aspiration Tuition Services Ltd | Education | 2022 |
| Aspirational Residential Developments Limited | Construction | 2017 |
| Aspire D Academy Limited | Health & social care | 2012 |
| Aspire D Online Ltd | Education | 2020 |
| Aspire Dental Practice Limited | Health & social care | 2024 |
| Aspire Wellness Limited | Health & social care | 2024 |
| Aspires H & P Ltd | Wholesale & retail | 2024 |
| Aspo Recruitment Ltd | Administrative & support | 2025 |
| Aspyra Technologies Ltd | Wholesale & retail | 1998 |
| Asset Films Ltd | Information & communication | 2012 |
| Assure FX Limited | Professional & scientific | 2019 |
| Assured Glazing Solutions Ltd | Construction | 2024 |
| Asta Strom Limited | Health & social care | 2008 |
| Aston Veer Law Company Ltd | Professional & scientific | 2021 |
| Astreon Dental Ltd | Health & social care | 2025 |
| Astrit Ltd | Hospitality | 2020 |
| Astrolink Ltd | Information & communication | 2025 |
| AT Fit OUT Group UK Ltd | Construction | 2017 |
| AT Global Beanz Ltd | Hospitality | 2026 |
| AT Optometry Limited | Health & social care | 2025 |
| AT Smiles Ltd | Health & social care | 2022 |
| AT3 Digital Labs Ltd | Professional & scientific | 2024 |
| Atelier Dental Limited | Health & social care | 2023 |