| Arzum Bakery Ltd | Manufacturing | 2020 |
| AS Building & Construction Limited | Construction | 2013 |
| AS Refrigeration and Air Conditioning Ltd | Professional & scientific | 2025 |
| Asabi Investment Properties Limited | Real estate | 2024 |
| Asante Sana Trading Limited | Wholesale & retail | 2020 |
| Ascend IQ Ltd | Information & communication | 2025 |
| Ascension Audio Limited | Information & communication | 2024 |
| Ascension Horizons Ltd | Real estate | 2023 |
| Ashake Health Limited | Health & social care | 2023 |
| Ashasi Ltd | Information & communication | 2022 |
| Ashbourne (UK) Limited | Administrative & support | 2007 |
| Ashleigh Gardens Estate Management Co Ltd | Households | 2007 |
| Ashurst IT Services Ltd | Information & communication | 2001 |
| Asia Express Fast Food Limited | Hospitality | 2013 |
| Asiko Clothing Ltd | Wholesale & retail | 2025 |
| Asiwaju Property Ltd | Hospitality | 2023 |
| ASK Primary Solutions Limited | Health & social care | 2023 |
| Aspen Photographic Services LLP | | 2003 |
| Aspire Global Trading Ltd | Wholesale & retail | 2020 |
| Aspire Vortex Limited | Wholesale & retail | 2026 |
| Asset IQ Solutions Ltd | Construction | 2018 |
| Assiduous Ltd | Other services | 2018 |
| Association of God's Heritage Provision for Children Ltd | Health & social care | 2018 |
| Assured Healthcare Ltd | Public administration | 2020 |
| Aston Clark Limited | Construction | 2019 |
| Astra Security Systems Limited | Administrative & support | 1979 |
| Astral Design Limited | Arts & recreation | 2019 |
| Astral Heating Services Limited | Construction | 2018 |
| Astral Solutions Limited | Wholesale & retail | 2019 |
| Astro Communications Limited | Information & communication | 1984 |
| Astro Global Care Ltd | Information & communication | 2022 |
| Astro Global Care Services Ltd | Administrative & support | 2025 |
| Astro I.T. Solutions Ltd | Information & communication | 2018 |
| Astro Network Services Ltd | Information & communication | 2018 |
| Astro Safety Solutions Ltd | Manufacturing | 2017 |
| Astro Technology Group Ltd | Extraterritorial | 2015 |
| Astrosyn Holdings Limited | Professional & scientific | 2024 |
| Astrosyn International Technology Limited | Manufacturing | 1974 |
| Astrosyn Limited | Professional & scientific | 1997 |
| Asya Kebab Limited | Hospitality | 2024 |
| AT & O Limited | Construction | 2019 |
| AT Bota's Limited | Health & social care | 2018 |
| AT Ident Ltd | Information & communication | 2015 |
| AT Plastering Kent Ltd | Construction | 2022 |
| ATA Air Conditioning Ltd | Construction | 2014 |
| ATA Solutions Limited | Wholesale & retail | 2026 |
| Atec DB Limited | Construction | 2014 |
| Atkins Hope Solicitors Limited | Professional & scientific | 2012 |
| Atkinson Labour Services Limited | Construction | 2011 |
| Atlas VA Ltd | Construction | 2016 |
| ATM 30 Ltd | Professional & scientific | 2022 |
| Atman Holdings Ltd | Real estate | 2023 |
| Atofi Ltd | Hospitality | 2022 |
| Atrium Construction Ltd | Construction | 2022 |
| Att.Allthethings Ltd | Wholesale & retail | 2025 |
| Attachment Hire Limited | Administrative & support | 2009 |
| Attachment Holdings Ltd | Real estate | 2023 |
| Attila Frozen Foods Limited | Wholesale & retail | 1985 |
| Attwood Farms Limited | Extraterritorial | 1996 |
| Atwal Investments 2 Limited | Hospitality | 2026 |
| Aubrin Rentals Limited | Real estate | 2013 |
| Auctium Ltd | Information & communication | 2024 |
| Aurora Grace Fine Jewellery Ltd | Manufacturing | 2019 |
| Aurora Metals Ltd | Wholesale & retail | 2025 |
| Aurum Rose Ltd | Real estate | 2025 |
| Austhan Property Management Ltd | Real estate | 2023 |
| Austin Care Ltd | Health & social care | 2025 |
| Austin Somers Site Services Ltd | Construction | 2026 |
| Autaway Limited | Information & communication | 2019 |
| Authentic 4 Autos Ltd | Wholesale & retail | 2025 |
| Authority Media Ltd | Information & communication | 2023 |
| Auticoin Ltd | Extraterritorial | 2015 |
| Autiquest Health Ltd | Extraterritorial | 2015 |
| Autiquest Ltd | Extraterritorial | 2015 |
| Auto Prog Ltd | Wholesale & retail | 2023 |
| Auto Rentals Ltd | Administrative & support | 2015 |
| Autograph Contracts Limited | Wholesale & retail | 2000 |
| Automatic Door Services Ltd | Construction | 2024 |
| Automatrix Kent Ltd | Wholesale & retail | 2024 |
| Automotive Vocational Training Limited | Administrative & support | 2008 |
| Autos 247 Ltd | Wholesale & retail | 2019 |
| Autosparx Vehicle Solutions Ltd | Wholesale & retail | 2023 |
| Autotrend Motor Services Limited | Wholesale & retail | 2003 |
| AV Property Collective Ltd | Real estate | 2026 |
| AVA Health Ltd | Professional & scientific | 2021 |
| Avalon FFC Ltd | Wholesale & retail | 2024 |
| Avandergrinten Ltd. | Information & communication | 2007 |
| Avanir Group Ltd | Financial services | 2026 |
| Avanir Management Ltd | Real estate | 2026 |
| Avanir Stays Ltd | Hospitality | 2026 |
| Avant PVT Ltd | Real estate | 2023 |
| AVD Contractors Ltd | Construction | 2015 |
| Avebury Computing Holdings Limited | Financial services | 2013 |
| Aveeco Cleaning Services Limited | Administrative & support | 2011 |
| Aveling Securities Limited | Real estate | 2014 |
| Aventro Property Group Ltd | Real estate | 2026 |
| Avenue Signs Limited | Manufacturing | 2001 |
| Averlle Ltd | Other services | 2025 |
| Avira Care Limited | Health & social care | 2026 |
| AVN Electrical Limited | Construction | 2023 |