| ADS Properties (South East) Limited | Real estate | 2025 |
| Advanced Bookkeeping and Consultancy Limited | Professional & scientific | 2024 |
| Advanced Therapy Systems Ltd | Wholesale & retail | 2015 |
| Advent Consulting Limited | Professional & scientific | 2023 |
| Adventure Riding Academy Limited | Arts & recreation | 2010 |
| AEA Commercial Limited | Professional & scientific | 2016 |
| AEI Holdings Limited | Financial services | 2001 |
| Aequitas Limited | Professional & scientific | 2006 |
| Aero Counsel Ltd | Professional & scientific | 2022 |
| Aero-K Ltd | Transport & logistics | 2025 |
| AESTHETICS4YOU Ltd | Health & social care | 2022 |
| AF Tax Solutions Ltd | Professional & scientific | 2015 |
| AFJ Consultants Limited | Professional & scientific | 2022 |
| Agar House Administration Limited | Households | 1999 |
| AGK Care Limited | Health & social care | 2025 |
| Agrawain Limited | Real estate | 2014 |
| Agronomy Capital Advisors Limited | Financial services | 2006 |
| Ahdw Services Ltd | Health & social care | 2025 |
| Ahle Limited | Real estate | 1998 |
| Air-Arms Limited | Professional & scientific | 2005 |
| Airedale Orthopaedics LLP | | 2024 |
| Airtight Fire & Security Systems Limited | Extraterritorial | 2010 |
| Airtight Security Systems Limited | Administrative & support | 2011 |
| Aj&Sons Cleaning Service Ltd | Administrative & support | 2024 |
| Aj's Baked Ltd | Hospitality | 2018 |
| Ajlg Limited | Financial services | 2013 |
| Akita Fencing Limited | Administrative & support | 2011 |
| Akita Land Management Limited | Administrative & support | 2014 |
| Akvideo Ltd | Information & communication | 2023 |
| Al's Barbers Limited | Other services | 2010 |
| Alberta Robins Ltd | Real estate | 2024 |
| Alchema Technologies Ltd | Real estate | 2009 |
| Alderman Associates Limited | Professional & scientific | 2023 |
| Aldermans Estates (Wavendon) Limited | Construction | 2019 |
| Aldermans Estates Ltd | Construction | 2010 |
| Aldermans Investments Ltd | Real estate | 2017 |
| Alderton Court Residents Association Limited | Households | 1959 |
| Alex Kader Advisory Ltd | Other services | 2023 |
| Alex Lloyd Commercial Ltd | Construction | 2015 |
| Alex Lloyd Developments Ltd | Construction | 2020 |
| Alex Lloyd LLP | | 2012 |
| Alex Lloyd Properties LLP | | 2013 |
| Aleysha Ltd | Health & social care | 2019 |
| ALL Maintenance & Property Services Limited | Construction | 2026 |
| ALL TOO Busy Solutions Limited | Information & communication | 2024 |
| ALL Wood Pallets Sussex Ltd | Wholesale & retail | 2026 |
| Allchorn Electrical Ltd | Construction | 2007 |
| Allen Developments (Sussex) Ltd | Extraterritorial | 2015 |
| Allesbee Ltd | Health & social care | 2025 |
| Allgooddesign Limited | Professional & scientific | 2026 |
| Allied Drinks Systems Limited | Wholesale & retail | 1998 |
| Allistone Electrical Limited | Construction | 2012 |
| Allium Farm Limited | Wholesale & retail | 2004 |
| Alpine Decorating Limited | Construction | 2005 |
| Alpine Woodworks Ltd | Construction | 2024 |
| Alta Vente Limited | Information & communication | 2004 |
| Altering Images Ltd | Construction | 2022 |
| Amalgamated Fish Boxes Limited | Professional & scientific | 1995 |
| Amber Plus Limited | Real estate | 2017 |
| AMD Digital Media Limited | Professional & scientific | 2025 |
| Amis Property Investment Limited | Real estate | 2023 |
| Amis Property Management Limited | Real estate | 2023 |
| AMP Groundcare Machinery Services Limited | Manufacturing | 2011 |
| Ampm Building Services Ltd | Construction | 2026 |
| Ampm Capital Ltd | Financial services | 2021 |
| Ampm Group Ltd | Financial services | 2026 |
| Ampollard Holdings Ltd | Financial services | 2023 |
| AMR Quest Limited | Arts & recreation | 2022 |
| Amstech Asbestos Removals Limited | Water & waste | 2014 |
| Amstech Inspections & Testing Limited | Water & waste | 2014 |
| Amstech Insulations Limited | Administrative & support | 2014 |
| Analog Labs Ltd | Manufacturing | 2022 |
| Analytical Components Limited | Manufacturing | 2015 |
| Ancient Holdings Limited | Wholesale & retail | 2024 |
| Anderberg Limited | Health & social care | 2023 |
| Andquest Limited | Other services | 2020 |
| Andrew J Pearcy Ltd | Administrative & support | 2009 |
| Andrew Skyrme Orthopaedics Limited | Health & social care | 2011 |
| Angela Marden Lettings Limited | Real estate | 2026 |
| Angharad Beck Hair Ltd | Other services | 2024 |
| Anglo-European Trustees LLP | | 2017 |
| ANH Minh Nails Limited | Other services | 2025 |
| Animaux Logistics Europe LLP | | 2020 |
| Animazing C.I.C. | Education | 2018 |
| Anivet Limited | Professional & scientific | 2013 |
| Anos Retail Services Ltd | Professional & scientific | 2020 |
| Ansell Investments Ltd | Professional & scientific | 2013 |
| Anthologie Floristry Limited | Wholesale & retail | 2018 |
| Antiques & Allsorts Ltd | Wholesale & retail | 2026 |
| Anusha Ltd | Wholesale & retail | 2022 |
| AOK Repairs Ltd | Manufacturing | 2025 |
| AP Data Resources Ltd | Information & communication | 2023 |
| AP Estate Agents Limited | Real estate | 2022 |
| AP Projects Sussex Limited | Administrative & support | 2025 |
| Apex Activities (South East) Limited | Education | 2025 |
| Apex Works Ltd | Construction | 2024 |
| Applehub Ltd | Other services | 2017 |
| Apps Precision Manufacturing Limited | Professional & scientific | 2026 |
| Apread Ltd | Real estate | 2026 |
| Aptus Healthcare LLP | | 2021 |