| A.E.M. Enterprises Limited | Professional & scientific | 1979 |
| A.H.A Design Limited | Extraterritorial | 2014 |
| A.J. Hammond (Builders) Limited | Construction | 1975 |
| A.J. Hassell Limited | Financial services | 1972 |
| A.J.H Meter Reading Services Ltd | Administrative & support | 2015 |
| A.M.Brown Ltd | Manufacturing | 2006 |
| A.M.E. Lift Engineering Ltd. | Construction | 1997 |
| A.P Enterprise Private Limited | Wholesale & retail | 2023 |
| A1 Building Contracts Limited | Construction | 2012 |
| A1 CSD Limited | Financial services | 2018 |
| A1 Developments South East Limited | Professional & scientific | 2016 |
| A1 IT Solutions Limited | Information & communication | 2001 |
| A1 Removals & Storage (Sussex) Limited | Administrative & support | 2004 |
| A1 Tropical Limited | Wholesale & retail | 2021 |
| A2 CSD Limited | Financial services | 2018 |
| A2B Property Group Ltd | Real estate | 2026 |
| A2B Property Management Ltd | Real estate | 2023 |
| A3 CSD Limited | Financial services | 2018 |
| A4 CSD Limited | Financial services | 2018 |
| A5 CSD Limited | Financial services | 2018 |
| Aaahaa Kalyanam Ltd | Other services | 2022 |
| Aapatel Limited | Real estate | 2022 |
| Aardian Ltd | Professional & scientific | 2020 |
| Aarish Ltd | Wholesale & retail | 2023 |
| AB Cleaning Services Limited | Administrative & support | 2025 |
| AB Connect Limited | Real estate | 2015 |
| AB Dentistry Ltd | Health & social care | 2022 |
| AB Electrician Ltd | Construction | 2015 |
| AB People Solutions Limited | Administrative & support | 2025 |
| Abacus Accounting Services (South) Ltd | Professional & scientific | 2019 |
| Abacus Flame Limited | Construction | 2009 |
| Abbeymart Timber Products Limited | Manufacturing | 2003 |
| Abbotsleigh Service Company Limited | Households | 1998 |
| Abby Holdings Ltd | Other services | 2021 |
| Abbyyz Ltd | Other services | 2019 |
| ABC Cobham Limited | Health & social care | 2024 |
| Aberfoyle Associates Limited | Households | 2006 |
| Abingworth Developments Ltd | Construction | 2009 |
| Abingworth Strategic Limited | Construction | 2013 |
| Able Plumbing Eastbourne Limited | Construction | 2017 |
| Able-Duct Limited | Manufacturing | 1980 |
| Abode 4 US Limited | Real estate | 2017 |
| Absolute Badger Limited | Wholesale & retail | 2024 |
| Absolute Edge Ltd | Information & communication | 2007 |
| Abundant Grace Limited | Health & social care | 2020 |
| ABX Coatings Limited | Wholesale & retail | 2013 |
| Abyssal Foundry Limited | Information & communication | 2025 |
| AC P&H Ltd | Construction | 2025 |
| Academy Soccer Coach Limited | Information & communication | 2010 |
| Academy Sports Coach Ltd | Information & communication | 2017 |
| Acar Taxi Ltd | Transport & logistics | 2024 |
| ACB Dental Limited | Health & social care | 2023 |
| Access Connect Limited | Education | 2016 |
| Accord Audio Visual Ltd | Administrative & support | 2023 |
| Accord Holdings (South East) Ltd | Financial services | 2023 |
| Accord.Me.Uk Limited | Professional & scientific | 2022 |
| Accountancy Options Limited | Extraterritorial | 2021 |
| Accountancy Software Solutions Limited | Information & communication | 2006 |
| Accurate Building Contractors Ltd | Construction | 2013 |
| Ace Decor Sussex Limited | Construction | 2022 |
| Ace Inflatables Limited | Administrative & support | 2021 |
| Ace Proficients Ltd | Education | 2022 |
| ACF Roofing Contractors Ltd | Construction | 2024 |
| ACG Tree Surgery Ltd | Administrative & support | 2019 |
| Acid Baby Studios CIC | Wholesale & retail | 2026 |
| Acocf Trustee Limited | Administrative & support | 2023 |
| Acorn Car Detailing Limited | Wholesale & retail | 2017 |
| Acorn Car Trading Limited | Wholesale & retail | 2021 |
| Acorn Upholstery Eastbourne Ltd | Wholesale & retail | 2008 |
| Acrd Consultants Limited | Financial services | 2021 |
| Acrefield Land Agent Ltd | Real estate | 2026 |
| Acrotex Limited | Arts & recreation | 1998 |
| ACS Controlled Demolition Ltd | Construction | 2011 |
| Action Company Events Ltd | Education | 2018 |
| Action Property Group Ltd | Construction | 2026 |
| Active Children Ltd | Hospitality | 2008 |
| Active Financial Planning Ltd | Financial services | 2018 |
| Active Wellness Clinic Ltd | Real estate | 2025 |
| Acute Admissions Limited | Health & social care | 2021 |
| Acute Financial Solutions Limited | Professional & scientific | 2015 |
| ACW Finance Ltd | Professional & scientific | 2025 |
| AD Buyers Club Ltd | Administrative & support | 2020 |
| AD Services Southern Ltd | Construction | 2016 |
| Adam Jacobs Photography Limited | Professional & scientific | 2013 |
| Adam Lofts Heating Limited | Professional & scientific | 2010 |
| Adam Mohammed ALI Limited | Health & social care | 2021 |
| Adam Rose-Alison Limited | Manufacturing | 2022 |
| Adaptation Design & Support Services Limited | Professional & scientific | 2011 |
| Adcox Limited | Professional & scientific | 2010 |
| Added Value Group Ltd | Education | 2024 |
| Addems & Hambling Limited | Construction | 2014 |
| Addy Dental Care Limited | Health & social care | 2008 |
| Adebayo Ogunbufunmi Design Studio Limited | Construction | 2016 |
| Adhdplay Ltd | Professional & scientific | 2025 |
| ADI Holdings Limited | Health & social care | 2022 |
| Adison Holdings Ltd | Households | 2022 |
| ADM Advisors Ltd | Professional & scientific | 2025 |
| Administration Company Limited | Administrative & support | 1995 |
| Admirals Reach (Eastbourne) Management Company Limited | Households | 1995 |
| Admiralty Court Flat Management Limited | Households | 2001 |