| Anglo-American Broadcasting Limited | Professional & scientific | 2016 |
| Anglo-American Property Corporation Limited | Extraterritorial | 1988 |
| Anglo-American Property Holdings Limited | Administrative & support | 2017 |
| Aniba Limited | Other services | 2015 |
| Anima Entertainment Ltd | Information & communication | 2023 |
| Animo Nobilis Limited | Administrative & support | 2018 |
| ANN Estate Ltd | Real estate | 2020 |
| Anna's Beauty House Limited | Other services | 2018 |
| ANP Senior Care Ltd | Health & social care | 2019 |
| Anthorne Park Management Limited | Households | 2006 |
| Anti Hippo Limited | Professional & scientific | 2025 |
| Antonica-James Property Limited | Real estate | 2024 |
| Anvega Ltd | Information & communication | 2026 |
| Anystage Productions Limited | Arts & recreation | 1996 |
| Anywhere Eyewear Limited | Professional & scientific | 2021 |
| AOE Consulting Limited | Professional & scientific | 2024 |
| Aomm Consulting Ltd | Professional & scientific | 2022 |
| AP IT Support Limited | Information & communication | 2020 |
| Apco Propco Ltd | Real estate | 2024 |
| Apco the Artichoke Ltd | Hospitality | 2013 |
| Apco the Feathers Ltd | Hospitality | 2013 |
| Apdale Limited | Professional & scientific | 2010 |
| Aperture Global Real Estate Limited | Real estate | 2025 |
| Apex Engineering & Consultants Group Ltd | Professional & scientific | 2026 |
| Apex Roofing and Gutters Ltd | Construction | 2022 |
| Apex Training Club Ltd | Arts & recreation | 2026 |
| Apexbrook (1999) Limited | Real estate | 1999 |
| Apexbrook (Minories) Limited | Real estate | 2000 |
| Apexbrook Dean Limited | Professional & scientific | 2004 |
| APH Advisory Services Ltd | Professional & scientific | 2025 |
| Aphrodite Corporate Services Ltd | Administrative & support | 2014 |
| Aplomb Childcare 2 Limited | Health & social care | 2021 |
| Aplomb Childcare Limited | Health & social care | 2018 |
| Apoly Trade Ltd | Wholesale & retail | 2013 |
| Apple Tree Life Sciences (UK) Limited | Financial services | 2019 |
| Applebarns Investments Ltd | Real estate | 2017 |
| Appleisports Limited | Manufacturing | 2024 |
| Applied Computer Concepts Limited | Information & communication | 1991 |
| Apply Mortgages Ltd | Financial services | 2018 |
| Approach Management Limited | Households | 2010 |
| Appsconsult Ltd | Information & communication | 2015 |
| Aprg Group Limited | Construction | 2025 |
| Apricot Marketing Services Ltd | Professional & scientific | 2019 |
| AQ Coaching Limited | Health & social care | 2023 |
| Aqua Coral Ltd | Wholesale & retail | 2024 |
| Aquagloria Ltd | Administrative & support | 2025 |
| Aqualona Products USA Ltd | Financial services | 2024 |
| Aquatecture Design Services Limited | Professional & scientific | 2021 |
| Aquila Property Investments (UK) Ltd | Administrative & support | 2012 |
| Arak Hair Ltd | Other services | 2025 |
| ARC Sourcing Ltd | Professional & scientific | 2013 |
| Arcadia Lounge Bar Club Ltd | Administrative & support | 2013 |
| Archers Close Service Management Limited | Real estate | 2016 |
| Archers Place South Street Bishops Stortford Management Limited | Households | 2007 |
| Archie Property Maintenance Limited | Professional & scientific | 2018 |
| Archival Publications International Limited | Information & communication | 1998 |
| Arcon Enterprises Limited | Professional & scientific | 2013 |
| Arcon Investments Limited | Professional & scientific | 2011 |
| ARD3 Investments Ltd | Real estate | 2021 |
| Arden Alex Management Limited | Real estate | 2024 |
| Ardourx Media Ltd | Arts & recreation | 2023 |
| Aren Associates Ltd | Real estate | 2022 |
| Arepo Solutions Limited | Information & communication | 1998 |
| Aria Beauty 10 Ltd | Wholesale & retail | 2026 |
| Ariana & Elysia Properties Ltd | Real estate | 2025 |
| Arihant Investments Ltd | Real estate | 2025 |
| Arihant Services Ltd | Administrative & support | 2025 |
| Arista Kids Ltd | Health & social care | 2017 |
| Arista Properties Ltd | Real estate | 2023 |
| Arkon PAY Limited | Construction | 2017 |
| Arlen Commercial Limited | Other services | 2017 |
| Arlen Properties Limited | Real estate | 1991 |
| Arlington Walk RTM Company Limited | Households | 2007 |
| Armani Properties Limited | Extraterritorial | 2003 |
| Arms Reach CIC | Education | 2024 |
| Art House Real Estate Ltd. | Professional & scientific | 2017 |
| Art of the Movies Limited | Wholesale & retail | 2016 |
| ART4 Electrical Ltd | Construction | 2022 |
| Arta EN6 Ltd | Wholesale & retail | 2024 |
| Artech Vision Ltd | Information & communication | 2019 |
| Artefactax Limited | Information & communication | 2025 |
| Artek Brothers Ltd | Real estate | 2026 |
| Artex Trading Limited | Administrative & support | 2008 |
| Arthur Nilsson Properties Ltd | Real estate | 2005 |
| Artio Global Investors Ltd | Financial services | 2011 |
| Artkurio Consultancy Ltd | Professional & scientific | 2016 |
| Artsman Limited | Administrative & support | 2022 |
| Arushi Limited | Wholesale & retail | 2010 |
| Aruvr Limited | Information & communication | 2018 |
| Arya Capital Investment Ltd | Financial services | 2025 |
| AS Accounting Ltd | Professional & scientific | 2021 |
| AS Care Investments Ltd | Real estate | 2022 |
| Asap Contractors Ltd | Construction | 2018 |
| Asap Gearbox Parts Limited | Wholesale & retail | 2017 |
| Ascroft Estates Limited | Real estate | 2025 |
| ASE Surveying Limited | Professional & scientific | 2017 |
| Asella Ltd | Wholesale & retail | 2019 |
| ASH Lake Limited | Information & communication | 2023 |
| ASH Property Portfolio Limited | Real estate | 2011 |
| Ashdale Property Management Ltd | Real estate | 2018 |