| Aspire & Develop Limited | Real estate | 2014 |
| Aspire Black Suffolk CIC | Professional & scientific | 2021 |
| Aspire Cars Ipswich Ltd | Wholesale & retail | 2015 |
| Aspire Clinical Psychological & Neuropsychological Services (Acpns) Limited | Health & social care | 2015 |
| Aspire Green Homes Limited | Construction | 2024 |
| Aspire Group Leisure Limited | Administrative & support | 2024 |
| Aspire Group of Companies Limited | Professional & scientific | 2024 |
| Aspire Maintenance Limited | Administrative & support | 2024 |
| Aspire Plastics Limited | Financial services | 2010 |
| Aspire Properties (Suffolk) Ltd | Real estate | 2023 |
| Asquith Financial Services Limited | Financial services | 2021 |
| Asse Food Services Ltd | Hospitality | 2025 |
| Assegai (Leathermarket) Limited | Real estate | 2007 |
| Assegai (Leathermarket) Partnership | | 2007 |
| Assemvra Project Consolidation Limited | Information & communication | 2026 |
| Asset Care Plus Ltd | Information & communication | 2025 |
| Asset Education | Education | 2015 |
| Asset Finance and Recovery Ltd | Financial services | 2016 |
| Assist Digital EU Limited | Information & communication | 2004 |
| Associated Construction and Engineering Ltd | Construction | 2018 |
| Association for Nutrition | Other services | 2008 |
| Association of British Mountainbike Guides | Arts & recreation | 2016 |
| Assured Capital Management Limited | Wholesale & retail | 2019 |
| Assured Enterprise Ltd | Real estate | 2019 |
| Assured Overland Transport Limited | Transport & logistics | 2013 |
| Assured PAY Ltd | Financial services | 2020 |
| AT Adminpremier Limited | Administrative & support | 2024 |
| AT Most Care Limited | Health & social care | 2022 |
| AT Physiotherapy Ltd | Health & social care | 2025 |
| AT Speed (Essex) Limited | Arts & recreation | 2017 |
| AT the 11TH Limited | Information & communication | 2016 |
| AT the Core Limited | Construction | 2025 |
| Atelier ADA Architectural and Associates Ltd | Professional & scientific | 2022 |
| Athena Structural Engineering Ltd | Professional & scientific | 2025 |
| Athene Logistik Limited | Transport & logistics | 2026 |
| Athera Studios Ltd | Education | 2025 |
| Athlete PI Holdings Ltd | Financial services | 2024 |
| Athlete Property Investment Limited | Real estate | 2017 |
| Athrumor Services Ltd | Professional & scientific | 2015 |
| Atim Consultancy Limited | Health & social care | 2022 |
| Atina Shipping (East Anglia) Limited | Transport & logistics | 1990 |
| ATL Aviation Ltd | Manufacturing | 2020 |
| Atlantic Management (INT) Ltd. | Information & communication | 2003 |
| Atlantiqo Ltd | Administrative & support | 2023 |
| Atlas (Ipswich) Management Company Limited | Households | 1984 |
| Atlas Trading GL Ltd | Wholesale & retail | 2021 |
| ATN Digital Limited | Information & communication | 2025 |
| ATN Plastics Ltd | Manufacturing | 2016 |
| ATOM14 Ltd | Professional & scientific | 2008 |
| Atomy Premium Ipswich Centre Ltd | Professional & scientific | 2023 |
| ATP Adhesive Systems Holding Ltd | Financial services | 2021 |
| ATR Contracting Services Ltd | Construction | 2022 |
| Atrac Limited | Construction | 2025 |
| ATS Roofing & Building Ltd | Construction | 2026 |
| Attellsoft Limited | Information & communication | 2021 |
| Attf Trans Ltd | Transport & logistics | 2017 |
| Attitude Inc Retail Limited | Wholesale & retail | 2011 |
| Attune Psychology Ltd | Education | 2024 |
| Attwells Property Company Limited | Real estate | 2017 |
| Attwells Solicitors LLP | | 2007 |
| ATV Parts Direct Ltd | Professional & scientific | 2015 |
| AU + 3 Ltd | Real estate | 2025 |
| AU Crafts Ltd | Wholesale & retail | 2024 |
| AUDI0COMINGS00N Ltd | Information & communication | 2021 |
| Audio Consulting and Training Limited | Professional & scientific | 2004 |
| Audiovia Limited | Information & communication | 2025 |
| Audley Court Consulting Limited | Real estate | 2014 |
| Audley Court Properties Ltd | Real estate | 2024 |
| Audrey Ludwig Training and Consulting Limited | Professional & scientific | 2024 |
| Audu TM Ltd | Construction | 2022 |
| Augerman Holdings Ltd | Financial services | 2024 |
| Augment Global Forwarding Ltd | Transport & logistics | 2025 |
| Augood Limited | Wholesale & retail | 2023 |
| Auksinis Opalas Ltd | Wholesale & retail | 2016 |
| Aulumbee Limited | Manufacturing | 2020 |
| Auoldies Ltd | Information & communication | 2007 |
| Aura Capital Management Limited | Professional & scientific | 2010 |
| Aura Digital Limited | Information & communication | 2019 |
| Aura Group Holdings Limited | Financial services | 2025 |
| Aura Media Group Limited | Professional & scientific | 2018 |
| Aura Yachts Limited | Wholesale & retail | 2024 |
| Aurel Tudor Ltd | Transport & logistics | 2019 |
| Aurorean Limited | Transport & logistics | 2010 |
| Aurum Roofing & Building Ltd | Construction | 2026 |
| Aurum Shellfish Ltd | Wholesale & retail | 2025 |
| Austhorpe Developments Limited | Real estate | 2020 |
| Austin Friars Steam Shipping Company Limited | Wholesale & retail | 2016 |
| Austwick Berry Estate Agents Limited | Real estate | 2009 |
| Austwick Berry Limited | Financial services | 2016 |
| Austwick Berry Property and Estate Management Limited | Real estate | 2016 |
| Authentic Floristry Limited | Wholesale & retail | 2026 |
| Authentic Indian Kitchen Limited | Hospitality | 2023 |
| Autism & Adhd Support & Training Ltd | Education | 2025 |
| Autism and Adhd | Education | 2013 |
| Auto Gear Hub Limited | Wholesale & retail | 2025 |
| Auto GT Ltd | Wholesale & retail | 2025 |
| Auto Paint & Blast Limited | Administrative & support | 2013 |
| Auto Repair & Service Ltd Ltd | Wholesale & retail | 2023 |
| Auto-Clean Limited | Administrative & support | 2023 |
| Autocare Suffolk Limited | Other services | 2023 |