| Aduloju Trading Limited | Wholesale & retail | 2026 |
| Adur Community Gateway CIC | Health & social care | 2021 |
| Adur Drinks Limited | Wholesale & retail | 2023 |
| Adur Investment Co. Limited | Construction | 1961 |
| Adur Lofts (Worthing) Limited | Households | 2018 |
| Adur Mortgages Limited | Financial services | 2007 |
| Adur Partners Limited | Professional & scientific | 2014 |
| Advance 6 Limited | Professional & scientific | 2013 |
| Advanced Freight Trading Capital Limited | Transport & logistics | 2019 |
| Advanced Nanostructured Materials Design and Consultancy (Anamad) Limited | Professional & scientific | 2018 |
| Advanced Property Construction Limited | Manufacturing | 2002 |
| Advanced Retail Technology Limited | Wholesale & retail | 2015 |
| Advanced Riding Techniques Limited | Education | 1998 |
| Advantage Management Group Limited | Administrative & support | 2000 |
| Advent Capital (Holdings) Ltd | Other services | 1995 |
| Advent Capital (NO. 3) Limited | Financial services | 2005 |
| Advent Capital (NO.2) Limited | Financial services | 2002 |
| Advent Capital Limited | Financial services | 1993 |
| Advent Underwriting Limited | Financial services | 1975 |
| Adventfs, Ltd | Information & communication | 2024 |
| Adventure and Shields LLP | | 2024 |
| Advert Area Limited | Information & communication | 2014 |
| Advice Cloud Limited | Professional & scientific | 2006 |
| Advizen Ltd | Professional & scientific | 2025 |
| AE Systems Ltd | Construction | 2023 |
| Aedcontractors Ltd | Construction | 2025 |
| Aegis Consulting Ltd | Professional & scientific | 2025 |
| AEO Properties Limited | Real estate | 2021 |
| Aeolus Limited | Professional & scientific | 2016 |
| Aerialist Ltd | Information & communication | 2025 |
| Aerofutures Limited | Professional & scientific | 2014 |
| Aeropro Cycling Limited | Manufacturing | 2019 |
| Aerospace Support Associates Limited | Transport & logistics | 1994 |
| Aerotrope Limited | Professional & scientific | 2005 |
| Aerotuck Ltd | Professional & scientific | 2026 |
| Aesthetics by AMY West Sussex Ltd | Other services | 2025 |
| Aesthetics by Eloise Ltd | Other services | 2019 |
| Aesthetics Cosmetics Ltd | Other services | 2024 |
| Aesthetology Ltd | Health & social care | 2017 |
| Aethelstone Properties Ltd | Households | 2025 |
| Aevasionn Ltd | Information & communication | 2026 |
| AF ENG Ltd | Construction | 2022 |
| Affective Productions Limited | Administrative & support | 2017 |
| Affiniti Finance Limited | Financial services | 2014 |
| African Centre for Development and Research Ltd | Other services | 2011 |
| African Night Fever Community Interest Company | Arts & recreation | 2013 |
| Afridazzles Limited | Manufacturing | 2025 |
| Afrikmark Ltd | Wholesale & retail | 2011 |
| Afro Hair Academy Ltd | Other services | 2021 |
| Afrori Books Ltd | Wholesale & retail | 2021 |
| Afsun Limited | Hospitality | 2025 |
| Aftc Fiscal Services UK Ltd | Information & communication | 2018 |
| After Five Ltd | Real estate | 2022 |
| After the Barre Ltd | Health & social care | 2020 |
| AG Marketing Consultancy Ltd | Professional & scientific | 2017 |
| Agapi Boating UK Limited | Wholesale & retail | 2026 |
| Agatka Limited | Manufacturing | 2009 |
| AGB (Church Road) Limited | Construction | 2001 |
| AGB (Hove) Limited | Real estate | 2021 |
| AGB Properties (Woking) Limited | Real estate | 2002 |
| AGB Reading 2020 Limited | Real estate | 2014 |
| AGB Reading LLP | | 2008 |
| AGB Security UK Ltd | Administrative & support | 2025 |
| AGB Workshop Services Limited | Wholesale & retail | 2025 |
| AGD Design Ltd | Manufacturing | 2022 |
| AGE of Reason UK Limited | Wholesale & retail | 2011 |
| AGE UK West Sussex Enterprises Limited | Financial services | 1998 |
| AGE UK West Sussex, Brighton and Hove | Health & social care | 2001 |
| Agencies International ( GB ) Ltd | Administrative & support | 2008 |
| Agentic Business Company Limited | Information & communication | 2025 |
| Agentis Health Group Ltd | Financial services | 2020 |
| Agents Property Solution Limited | Real estate | 2014 |
| Aggregate Communications Ltd | Professional & scientific | 2016 |
| AGH Elecs Limited | Manufacturing | 2025 |
| Agile Adaptations Ltd | Administrative & support | 2021 |
| Agile Done Ltd | Information & communication | 2023 |
| Agile Hearts and Minds Limited | Administrative & support | 2015 |
| Agile Strategy Design Ltd | Professional & scientific | 2015 |
| Agile Trading Limited | Financial services | 2014 |
| Agilitas IT Solutions Limited | Administrative & support | 1990 |
| Agiloro Limited | Information & communication | 2026 |
| Agimagi Ltd | Health & social care | 2024 |
| Aging Geek Games Ltd | Information & communication | 2023 |
| AGJ Chauffeur Services Limited | Transport & logistics | 2014 |
| Agnic Limited | Extraterritorial | 2025 |
| Agonda Projects Limited | Information & communication | 2020 |
| Agora Gynaecology and Fertility Centre Ltd | Health & social care | 2005 |
| Agrasta Market Ltd | Information & communication | 2023 |
| Agricola Global Limited | Administrative & support | 2015 |
| Agrifoam Ltd | Wholesale & retail | 2023 |
| Agriturismo Ltd | Hospitality | 2025 |
| AGS 360 Careers Limited | Extraterritorial | 2012 |
| AGS Cleaning Services Limited | Extraterritorial | 2006 |
| AGS One Group Limited | Extraterritorial | 2010 |
| AGS Recruitment Limited | Extraterritorial | 2008 |
| AGS Renovations Limited | Extraterritorial | 2006 |
| AGS Safety Critical Limited | Extraterritorial | 2006 |
| AGS Support Services Limited | Transport & logistics | 2012 |
| Aguachica Ltd | Wholesale & retail | 2019 |
| Agymelo Ltd | Professional & scientific | 2017 |