| Areyou - Training and Consultancy CIC | Other services | 2017 |
| Argan Group Limited | Construction | 2025 |
| Argan Homes Limited | Construction | 2018 |
| Argan Property Solutions Ltd | Real estate | 2022 |
| Argents Auctioneers Limited | Administrative & support | 2025 |
| Argomax Limited | Information & communication | 2003 |
| Ariael Limited | Wholesale & retail | 2016 |
| Aries Embroidery Limited | Manufacturing | 2001 |
| Arinkarinfu Ltd | Professional & scientific | 2024 |
| Aris Konstantopoulos Limited | Health & social care | 2015 |
| Aristia Limited | Wholesale & retail | 1999 |
| Arland Developments Limited | Construction | 2026 |
| Arland Lettings Limited | Real estate | 2023 |
| Armintex Ltd | Extraterritorial | 2023 |
| Armoury Advancements U.K. Ltd | Wholesale & retail | 2026 |
| Armrite Pro Clean Limited | Other services | 2025 |
| Arnoldas Couriers Ltd | Transport & logistics | 2018 |
| ARO Market Shop Limited | Wholesale & retail | 2024 |
| ARO Mini Shop Ltd | Wholesale & retail | 2026 |
| Aroha Staffing Solutions Limited | Administrative & support | 2022 |
| Aroma-Craft Coffee Roasters Ltd | Wholesale & retail | 2023 |
| Aroona Ltd | Information & communication | 2016 |
| Arrange Care Services Ltd | Health & social care | 2023 |
| Arribada Initiative C.I.C. | Information & communication | 2018 |
| Arrow Business Consultancy Services Limited | Professional & scientific | 2017 |
| Arrow Suspended Ceilings + Interiors Limited | Construction | 2011 |
| Art on Film Limited | Professional & scientific | 2023 |
| Art on Metal Ltd | Manufacturing | 2025 |
| Art Property (IW) Ltd | Real estate | 2023 |
| Art Solution Properties Ltd | Real estate | 2025 |
| Art Space Portsmouth Limited | Education | 1981 |
| Art UP (Portsmouth) CIC | Arts & recreation | 2024 |
| Artemas Projects Limited | Information & communication | 2016 |
| Artemis Solutions Limited | Information & communication | 2015 |
| Artful Dodgers Boxing Acadamy Ltd | Arts & recreation | 2022 |
| Artifex Projects Ltd | Construction | 2015 |
| Artificial Grass Landscapes Ltd | Construction | 2016 |
| Artisan Europe Ltd | Administrative & support | 2025 |
| Artisan Kitchens and Furniture Ltd | Wholesale & retail | 2023 |
| Artisan Recruit Ltd | Administrative & support | 2015 |
| Artisan Recruitment Group Ltd | Financial services | 2025 |
| Artscapy Finance Ltd | Financial services | 2024 |
| Artscapy Ltd | Information & communication | 2020 |
| Artscapy Trading Ltd | Wholesale & retail | 2025 |
| Arumugam Retailers Ltd | Wholesale & retail | 2025 |
| Arun Croft Meat and Poultry Ltd | Wholesale & retail | 2020 |
| Arun Fastener Company Limited | Wholesale & retail | 2001 |
| Arun Integrated Care PCN Limited | Health & social care | 2023 |
| Arundel Aviaries and Fisheries Limited | Wholesale & retail | 1974 |
| Arundel Court Management (Southsea) Limited | Hospitality | 1985 |
| Arvaan Group Ltd | Wholesale & retail | 2026 |
| Arxresidentialsurveyors Ltd | Professional & scientific | 2025 |
| AS Retreats LLP | | 2024 |
| AS Shopfitting Ltd | Manufacturing | 2021 |
| Asant' Healthy Kitchen Limited | Wholesale & retail | 2024 |
| Ascot & Finch Ltd | Wholesale & retail | 2020 |
| Asgard Carpentry Ltd | Construction | 2025 |
| ASH Copse Mortgages Limited | Financial services | 2011 |
| ASH Distribution Ltd | Transport & logistics | 2024 |
| ASH Lodge Residents Association Limited | Households | 1984 |
| ASH S Consultancy Limited | Construction | 2022 |
| Ashby’S Southsea Limited | Hospitality | 2019 |
| Ashdene Romsey Management Company Limited | Real estate | 2011 |
| Asher Design & Print Limited | Manufacturing | 2008 |
| Ashhawk Enterprises Limited | Real estate | 2024 |
| Ashhawk Group Limited | Financial services | 2024 |
| Ashling House RTM Company Limited | Households | 2009 |
| Ashling Lettings Limited | Real estate | 2022 |
| Ashton Pictures Ltd | Information & communication | 2025 |
| Ashwood Solar Ltd | Construction | 2011 |
| Asia Property Limited | Real estate | 2012 |
| Asian Fried Chicken Ltd | Hospitality | 2025 |
| ASJ Accounting Limited | Professional & scientific | 2017 |
| ASJ Estates Limited | Real estate | 2017 |
| ASJ Global Limited | Real estate | 2002 |
| Askra Trading Limited | Professional & scientific | 2025 |
| Aspenway Limited | Real estate | 1993 |
| Asphalt UK (Plant) Limited | Administrative & support | 2014 |
| Aspire Aerospace Ltd | Manufacturing | 2018 |
| Aspire Personalised Support Ltd | Health & social care | 2010 |
| ASR Retail Limited | Wholesale & retail | 2020 |
| Asset Energy Limited | Manufacturing | 2003 |
| Asset Wealth Creation Limited | Financial services | 2015 |
| Associated Couriers UK Limited | Transport & logistics | 2022 |
| Association for Families of Independent Schooling (Afis) C.I.C. | Other services | 2025 |
| Assure Accoutancy Services Ltd | Professional & scientific | 2023 |
| Assure Property Investments Ltd | Real estate | 2020 |
| Assured Comms UK Ltd | Administrative & support | 2016 |
| Assured Independent Financial Services Limited | Financial services | 2009 |
| Asta Technology UK Ltd | Education | 2008 |
| Astares Direct Limited | Wholesale & retail | 2019 |
| Astares Menswear Limited | Wholesale & retail | 2017 |
| Aster Care Limited | Administrative & support | 2007 |
| Aster Consulting Ltd | Information & communication | 2014 |
| Aster Health Ltd | Wholesale & retail | 2025 |
| Asteriks Care Limited | Health & social care | 2023 |
| Astex Educational Advisors UK Limited | Education | 2009 |
| Aston Products Limited | Manufacturing | 1997 |
| Astonglen Associates Limited | Professional & scientific | 2014 |
| Astra Properties Ltd | Real estate | 2023 |