| ARK Made Ltd | Construction | 2025 |
| ARK Resourcing Limited | Administrative & support | 2024 |
| Arkalo Ltd | Information & communication | 2018 |
| Arkalo Properties Ltd | Real estate | 2020 |
| Arkescope Limited | Financial services | 2017 |
| Arkn Properties Ltd | Real estate | 2025 |
| Arminas S Ltd | Transport & logistics | 2018 |
| Armoury Lift Solutions Ltd | Professional & scientific | 2023 |
| Armstrong Energy Consultants Limited | Professional & scientific | 2017 |
| Arnone Investments Ltd | Real estate | 2021 |
| Arnoosh UK Limited | Hospitality | 2016 |
| Aroma Icecream Limited | Manufacturing | 1999 |
| Aroma Property Management Limited | Real estate | 2018 |
| Around the Clock Locks Ltd | Administrative & support | 2001 |
| Arro Properties Ltd | Real estate | 2016 |
| Arrow Office Equipment Limited | Wholesale & retail | 2002 |
| Art by SAN B Limited | Arts & recreation | 2020 |
| Art-Ar Limited | Other services | 2014 |
| Artemedia Loops Ltd. | Information & communication | 1996 |
| Artistik Film Limited | Information & communication | 2011 |
| Artley Prints Ltd | Manufacturing | 2022 |
| Arush & Ayra Homes Ltd | Real estate | 2025 |
| Arya Dental Limited | Health & social care | 2007 |
| Arya Foods Ltd | Hospitality | 2025 |
| Aryaan Limited | Health & social care | 2024 |
| Aryaan Property Investments Ltd | Real estate | 2025 |
| Arys Lighting Limited | Wholesale & retail | 2026 |
| AS Construction Maintenance & Management Limited | Construction | 2019 |
| Asaro Property Solutions Limited | Real estate | 2025 |
| ASB F&C Ltd | Hospitality | 2024 |
| ASB Lifts Ltd | Manufacturing | 2011 |
| Ased 91 Ltd | Real estate | 2018 |
| Ashbrooke Consulting Limited | Professional & scientific | 2024 |
| Ashdale Joinery Limited | Construction | 2020 |
| Ashdon Residence Ltd | Construction | 2025 |
| Ashela Limited | Hospitality | 2026 |
| Ashgrove Residential Care Home Ltd | Health & social care | 2020 |
| Ashley Pettit Dental Limited | Health & social care | 2019 |
| Ashleysbuilding Limited | Construction | 2012 |
| Ashmere Solutions Ltd | Professional & scientific | 2022 |
| Ashwood Farm Commercial Limited | Real estate | 2026 |
| ASJ Media Ltd | Other services | 2021 |
| Askco Limited | Wholesale & retail | 2009 |
| Askk Holdings Limited | Financial services | 2016 |
| Askk IT Solutions Limited | Information & communication | 2007 |
| Aslan Baristas 1 Limited | Hospitality | 2025 |
| Aslan Fitness 1 Limited | Arts & recreation | 2024 |
| Aslan Fitness Limited | Arts & recreation | 2023 |
| ASM Construction Essex Limited | Construction | 2025 |
| ASM Smart Properties Ltd | Professional & scientific | 2024 |
| ASM Variety Store Limited | Wholesale & retail | 2024 |
| Asm-Electrical Services Ltd | Other services | 2015 |
| Asm-Fire & Security Ltd | Administrative & support | 2024 |
| ASN Properties Limited | Real estate | 2020 |
| Asorti Food Ltd | Wholesale & retail | 2013 |
| Asorti Limited | Wholesale & retail | 2006 |
| Asorti UK Limited | Other services | 2009 |
| Aspiration Candles Ltd | Wholesale & retail | 2025 |
| Aspire Premises UK Ltd | Real estate | 2017 |
| Aspray Consultancy Limited | Information & communication | 2008 |
| Assetmesh Ltd | Information & communication | 2026 |
| Aston Estates (Tamworth) Limited | Real estate | 2023 |
| Astonish Services Ltd | Administrative & support | 2024 |
| Astrid House Management Limited | Real estate | 2026 |
| Astwood Investments Limited | Real estate | 2017 |
| ATA Cars Ltd | Wholesale & retail | 2017 |
| Atelier Soleil Ltd | Wholesale & retail | 2025 |
| ATG Consultancy Ltd | Administrative & support | 2019 |
| Athena CRM Ltd | Information & communication | 2024 |
| Athenian Hastings Limited | Hospitality | 2024 |
| Athlytics Ltd | Information & communication | 2025 |
| ATK Electrical Services Ltd | Construction | 2016 |
| Atlantic Glazing Ltd. | Construction | 2018 |
| Atlas Building & Carpentry Ltd | Construction | 2019 |
| Atlas Restoration Limited | Manufacturing | 1999 |
| Atlas South East Services Limited | Real estate | 2011 |
| Atlas Surveying & Building Consultancy Ltd | Real estate | 2025 |
| Atlo Air Conditioning Ltd | Construction | 2025 |
| Atomhouse Ltd | Administrative & support | 2025 |
| ATR Services Limited | Wholesale & retail | 2023 |
| Atseg Ltd | Professional & scientific | 2016 |
| Attach Creative Ltd | Professional & scientific | 2016 |
| Attalfair Services Limited | Information & communication | 2020 |
| Attreed Investments Ltd | Real estate | 2020 |
| Atvocal Ltd | Manufacturing | 2022 |
| Atwt Engineering Consultancy Limited | Professional & scientific | 2017 |
| Audioporn Records Ltd. | Information & communication | 2013 |
| Audley House (Berkhamsted) Limited | Real estate | 2013 |
| Audrys Painting and Decorating Ltd | Manufacturing | 2026 |
| Aulluck Holdings Ltd | Real estate | 2017 |
| Aura Creation Homes Limited | Real estate | 2017 |
| Aura Creations Ltd | Manufacturing | 2025 |
| Aura Health & Beauty Ltd | Other services | 2025 |
| Aura Residential Ltd | Real estate | 2012 |
| Aurgold Transport Ltd Limited | Transport & logistics | 2025 |
| Aurora Window Cleaning Ltd | Administrative & support | 2026 |
| Auroracap Limited | Real estate | 2022 |
| Authentic Italian Ltd | Hospitality | 2019 |
| Authority Cleaning Limited | Administrative & support | 2024 |
| Autocircuit Solutions Limited | Wholesale & retail | 2025 |