| Adam Sims and Company Limited | Professional & scientific | 2011 |
| Adaptive Automation Ltd | Professional & scientific | 2024 |
| Adpilotpro Ltd | Information & communication | 2025 |
| Adur Design Solutions Ltd | Information & communication | 2016 |
| Advance Orthopaedic Care Limited | Health & social care | 2011 |
| Advanced Climate Technology Limited | Professional & scientific | 1995 |
| Advanced Energy Industries U.K. Limited | Professional & scientific | 1993 |
| Advanced Materials Ltd. | Manufacturing | 1998 |
| Advanced Security Ltd | Administrative & support | 2023 |
| Adventrio Ltd | Information & communication | 2023 |
| Adventure Alchemy Ltd | Administrative & support | 2025 |
| Aegir Plumbing and Heating Ltd | Construction | 2023 |
| Aerial Care UK Ltd | Administrative & support | 2013 |
| Aesacs Limited | Administrative & support | 2019 |
| Aesthetic & Beauty Services UK Ltd | Other services | 2020 |
| Aevris Ltd | Information & communication | 2023 |
| Affine Films Ltd | Information & communication | 2023 |
| Affluent Management Limited | Real estate | 2024 |
| Afwood Limited | Financial services | 2021 |
| AHEAD4BUSINESS Ltd | Administrative & support | 2015 |
| AI Agency Group Ltd | Information & communication | 2025 |
| Airside Business Centre Ltd | Real estate | 2025 |
| AJ Terry Ltd | Wholesale & retail | 2024 |
| AJS Gym Ltd. | Arts & recreation | 2016 |
| AJT Showers Ltd. | Administrative & support | 2018 |
| Ajwc Property Ltd | Real estate | 2022 |
| AK Leaflet Distribution Ltd | Professional & scientific | 2021 |
| Akin Consulting Ltd | Professional & scientific | 2021 |
| Albion Freehold Limited | Real estate | 2007 |
| Aldwick Place Residents Association Limited | Households | 1967 |
| Alexander Terrace Management Company Limited | Households | 2006 |
| Alfamed Healthcare and Security Services Ltd | Health & social care | 2016 |
| ALI Além Ltd | Wholesale & retail | 2025 |
| ALL in Health Clubs Ltd | Arts & recreation | 2023 |
| ALL Saints Preschool Ltd | Education | 2011 |
| Alleeez Limited | Professional & scientific | 2017 |
| Alnea Consulting Limited | Professional & scientific | 2015 |
| Alpha Catering Equipment Limited | Transport & logistics | 1995 |
| Alpha Door Solutions Ltd | Construction | 2024 |
| Alpha Homes & Property Ltd | Real estate | 2022 |
| Alphera Limited | Real estate | 2001 |
| Altitude HR Ltd | Administrative & support | 2018 |
| Amaf Property Investments Ltd | Households | 2022 |
| Amateur Bowling Circuit Ltd | Arts & recreation | 2025 |
| Ambacare Limited | Health & social care | 1997 |
| Ambion Healthcare Ltd | Health & social care | 2025 |
| Ameesal Consulting Limited | Health & social care | 2017 |
| Amenic Court Management Limited | Households | 1989 |
| Amma Events Ltd | Hospitality | 2026 |
| Andrena Regulatory Services Ltd | Professional & scientific | 2012 |
| Andy Reeves Limited | Professional & scientific | 2014 |
| Angal Collecting Boxes & Devices Limited | Other services | 1989 |
| Angal Limited | Professional & scientific | 1992 |
| Angel White Aesthetics Ltd | Other services | 2022 |
| Anglecourt Limited | Real estate | 1993 |
| Angmering on Sea Estate Residents Association Limited | Other services | 2006 |
| Angmering Village Greens Ltd | Wholesale & retail | 2021 |
| ANH Finance Limited | Real estate | 2022 |
| Anima Sarda Ltd | Professional & scientific | 2018 |
| Anna Muggeridge Media Ltd | Information & communication | 2022 |
| Anthony’S Fast Food Ltd | Hospitality | 2023 |
| APH Project Management & Construction Ltd | Construction | 2024 |
| Apple Van Hire Sussex Ltd | Administrative & support | 2012 |
| Appledore Green Management Company Limited | Households | 2019 |
| Appletrees (Angmering) Estate Limited | Households | 1974 |
| Aquagas (Sussex) Plumbing & Heating Solutions Ltd | Construction | 2024 |
| Aquaveil Care Ltd | Administrative & support | 2026 |
| Aranea Creations Limited | Information & communication | 2007 |
| Arcade Bookshop Limited | Wholesale & retail | 2025 |
| ARCANGEL888 Ltd | Other services | 2025 |
| Arch Construction (West Sussex) Ltd | Construction | 2025 |
| Arch Construction Sussex Ltd | Construction | 2019 |
| Arch Enclosures Limited | Construction | 2011 |
| Arien Graphics Limited | Information & communication | 2008 |
| Arkyard Agency Limited | Professional & scientific | 2025 |
| Arkyard Limited | Professional & scientific | 2016 |
| Arlo Willow Properties Ltd | Real estate | 2026 |
| Armoury Paint Supplies Ltd | Wholesale & retail | 2023 |
| Arnica Property Ltd | Construction | 2025 |
| Arolla Tree Care Ltd | Administrative & support | 2021 |
| Arran Blair Hairdressing Limited | Other services | 2022 |
| Art on Wood Ltd | Construction | 2018 |
| ARU Domusu Ltd | Real estate | 2025 |
| Arun Angling Limited | Wholesale & retail | 2003 |
| Arun Audio Productions Limited | Information & communication | 2022 |
| Arun Brickwork Limited | Construction | 2020 |
| Arun Canvas and Trimming Limited | Manufacturing | 2012 |
| Arun Community Church | Other services | 2004 |
| Arun Community Church: Wickbourne Centre | Education | 2004 |
| Arun Court RTM Company Limited | Real estate | 2010 |
| Arun Creative Limited | Information & communication | 2019 |
| Arun Decorators Ltd | Construction | 2017 |
| Arun Drying Solutions Ltd | Manufacturing | 2014 |
| Arun Drylining Ltd | Construction | 2023 |
| Arun Fencing & Paving Ltd | Manufacturing | 2018 |
| Arun Goldsmiths Co. Limited | Wholesale & retail | 1960 |
| Arun Group Limited | Wholesale & retail | 2015 |
| Arun International (Power) Limited | Manufacturing | 1991 |
| Arun Language Training & Recruitment Ltd | Education | 2015 |
| Arun Microelectronics Limited | Manufacturing | 1981 |