| Asat Consulting Ltd | Professional & scientific | 2018 |
| Asaw Group Ltd | Professional & scientific | 2019 |
| Ascender Design Limited | Information & communication | 2006 |
| Ascertra-Searoc Ltd. | Professional & scientific | 2007 |
| Asdug Recycling Limited | Administrative & support | 2005 |
| Asen Capital Advisors LLP | | 2026 |
| Ashacre Limited | Administrative & support | 1998 |
| Ashacre Scaffolding Limited | Construction | 2012 |
| Ashburner Building Services Ltd | Construction | 2025 |
| Ashchurch Partners Limited | Real estate | 2001 |
| Ashcroft Brickwork Limited | Construction | 2024 |
| Ashcroft Developments (Sussex) Ltd | Households | 2024 |
| Ashcroft Support Solutions Ltd | Administrative & support | 2025 |
| Ashe Lines Property Ltd | Real estate | 2023 |
| Ashgrove Holdings LLP | | 2013 |
| Ashgrove Homes (Europe) LLP | | 2013 |
| Ashley Thompson Photography Ltd | Professional & scientific | 2023 |
| Ashley's Meadow Ltd | Hospitality | 2022 |
| Ashling Associates Limited | Administrative & support | 2023 |
| Ashling Cricket Ground Limited | Real estate | 2026 |
| Ashling Farms Limited | Agriculture & fishing | 2017 |
| Ashling Park Estate Ltd. | Agriculture & fishing | 2011 |
| Ashling Partners Limited | Construction | 2019 |
| Ashmead Properties Limited | Construction | 1987 |
| Ashran Holdings Ltd | Real estate | 2018 |
| ASK WHY Limited | Professional & scientific | 2012 |
| Aspect Builders Ltd | Construction | 2004 |
| Aspect Properties 88 Ltd | Real estate | 2021 |
| Aspect Roofing Specialist Ltd | Construction | 2026 |
| Aspire Country Homes Limited | Real estate | 2011 |
| Asset Defence Associates Limited | Extraterritorial | 2011 |
| Asset Intelligence Ltd | Real estate | 2016 |
| Assidium Group Limited | Professional & scientific | 2023 |
| Astar Carpenters Limited | Manufacturing | 2017 |
| Astons of Sussex Ltd | Real estate | 2003 |
| Astons Property Management Ltd | Real estate | 2010 |
| Astound Group Ltd | Information & communication | 2018 |
| Astra Financial Services Limited | Administrative & support | 2018 |
| Astrea Limited | Financial services | 1990 |
| AT Ease With Equines CIC | Health & social care | 2023 |
| Ataka Management Limited | Professional & scientific | 2021 |
| Atlantic Oceanic (UK) Ltd | Transport & logistics | 2019 |
| Atomise-Sec Limited | Information & communication | 2012 |
| Atph Limited | Financial services | 2022 |
| Attendance Plus Limited | Education | 2016 |
| Attic Attack Toys & Games Ltd | Wholesale & retail | 2023 |
| Atty & Smart Limited | Wholesale & retail | 2014 |
| Audiat Ltd | Professional & scientific | 2019 |
| Augury Holdings Limited | Financial services | 2020 |
| Augusta House Residents Limited | Households | 1995 |
| Aurelian Interiors Ltd | Construction | 2015 |
| Aurelius Motors Limited | Wholesale & retail | 2026 |
| Aurora Consulting Services Ltd | Administrative & support | 2023 |
| Aurora Counselling Ltd | Health & social care | 2019 |
| Aurora Medical Limited | Professional & scientific | 2010 |
| Aurum Grove Limited | Manufacturing | 2021 |
| Austin Structures Limited | Professional & scientific | 2022 |
| Auto Turned Products (Northants) Limited | Extraterritorial | 1962 |
| Auto-Kinetic Ltd | Professional & scientific | 2010 |
| Autochron Limited | Administrative & support | 2001 |
| Autoev Limited | Administrative & support | 2018 |
| Autoexec Solutions Limited | Professional & scientific | 1997 |
| Autoflash Photography Limited | Information & communication | 2014 |
| Autologous Therapies Ltd | Administrative & support | 2010 |
| Automated Data Solutions Limited | Information & communication | 2020 |
| Automatic Gate Systems Limited | Construction | 2005 |
| Automation Management Holdings Limited | Financial services | 2025 |
| Automotivo Limited | Professional & scientific | 2017 |
| Autonomass Limited | Professional & scientific | 2024 |
| Autotechnics Chichester Limited | Wholesale & retail | 1999 |
| Autumn Grass UK Limited | Professional & scientific | 2015 |
| AV Connect Events Limited | Administrative & support | 2012 |
| Avant Garde Developments Ltd | Construction | 2018 |
| Avant Garde Management & Consultancy Ltd | Construction | 2016 |
| Avatar Partners Ltd | Real estate | 2021 |
| Avoltaev Ltd | Wholesale & retail | 2026 |
| Avoncross Ornamentals Limited | Agriculture & fishing | 2000 |
| AWS Pumps Limited | Manufacturing | 2022 |
| AWX Technologies Limited | Manufacturing | 2024 |
| AXB Property Development Limited | Construction | 2020 |
| AXB Property Limited | Real estate | 2017 |
| Axiom (UK) Limited | Information & communication | 1991 |
| Axiom Product Development Holdings Ltd | Manufacturing | 2019 |
| Axiom Product Development Ltd | Manufacturing | 2016 |
| Ayad Properties Limited | Real estate | 2018 |
| Ayda Baghernejad Limited | Other services | 2015 |
| Aylen Autos Limited | Wholesale & retail | 2012 |
| Ayre Family Investments Limited | Financial services | 2025 |
| Ayres Developments Ltd | Construction | 2015 |
| Azeezz Barber Ltd | Other services | 2023 |
| Azidale Ltd | Health & social care | 2022 |
| Aztec Computers Limited | Information & communication | 2001 |
| Azulado Ltd | Information & communication | 2018 |
| Azure Cleaning Services Limited | Administrative & support | 2015 |
| B & J Haughey Ltd | Professional & scientific | 2016 |
| B & K O'Dwyer Limited | Construction | 2003 |
| B a Electricals Ltd | Construction | 2020 |
| B B Crinion Limited | Construction | 2012 |
| B J Sports Ltd | Arts & recreation | 2013 |
| B J W Landscapes Limited | Administrative & support | 2025 |