| Arthur Marine Services Ltd | Professional & scientific | 2018 |
| Arthur Rose Projects Ltd | Construction | 2024 |
| Arthur Spence Limited | Wholesale & retail | 2019 |
| Arthur-Ross REG Consultants Ltd | Professional & scientific | 2017 |
| Articulate (London) Ltd | Information & communication | 2011 |
| Articulate Concepts Ltd | Information & communication | 2021 |
| Articulate Homes Ltd | Construction | 2025 |
| Artifacts Attic Enterprises Ltd | Wholesale & retail | 2025 |
| Artificial Intelligence and Mathematics Research LAB Ltd | Professional & scientific | 2024 |
| Artificiel Ltd | Professional & scientific | 2020 |
| Artificium Ltd | Information & communication | 2026 |
| Artisanpremiersolutions Ltd | Hospitality | 2024 |
| Artist Archive Ltd | Wholesale & retail | 2022 |
| Artlab Industries Ltd | Wholesale & retail | 2019 |
| Arto.Energy Limited | Energy | 2014 |
| Artofwall Ltd | Professional & scientific | 2025 |
| Artouch Limited | Professional & scientific | 2024 |
| Arts Collective Ltd | Education | 2020 |
| Arts, Theatre and Heritage Ltd | Professional & scientific | 2019 |
| Artsymix Ltd | Information & communication | 2025 |
| Artyc Ltd | Information & communication | 2026 |
| Arukah Consultancy Limited | Professional & scientific | 2025 |
| Arukah Health Ltd | Health & social care | 2022 |
| Arvani Life Sciences Ltd | Wholesale & retail | 2026 |
| Arventa Limited | Wholesale & retail | 2025 |
| ARX Health & Safety Ltd | Professional & scientific | 2025 |
| AS Car Dismantlers Limited | Wholesale & retail | 2017 |
| AS Care Services Ltd | Health & social care | 2025 |
| AS Motor Engineers Ltd | Wholesale & retail | 2012 |
| AS Old AS I AM Limited | Administrative & support | 2023 |
| AS Plumbing & Heating Services Limited | Construction | 2015 |
| AS YOU ARE Ltd | Professional & scientific | 2025 |
| AS7 Group Ltd | Extraterritorial | 2025 |
| Asake Orekelewa Ltd | Wholesale & retail | 2025 |
| Asanti Pictures Ltd | Information & communication | 2025 |
| Ascend Academy Ltd | Education | 2021 |
| Ascend Collective Properties Ltd | Real estate | 2026 |
| Ascend General Consultants Ltd | Professional & scientific | 2025 |
| Ascenta Advisory Ltd. | Wholesale & retail | 2024 |
| Asclepius Group Limited | Information & communication | 2026 |
| ASD2 Limited | Other services | 2023 |
| ASH Estates (UK) Ltd | Construction | 2009 |
| ASH Healthcare Services Limited | Health & social care | 2022 |
| Asha Modi Ltd | Health & social care | 2019 |
| Ashamo Ltd | Real estate | 2024 |
| Ashb Ltd | Education | 2022 |
| Ashcrest Digital Ltd | Information & communication | 2026 |
| Ashfield Grange (Great Ashfield) Management Company Limited | Households | 2006 |
| Ashford & Abraham Holdings Ltd | Financial services | 2024 |
| Ashford & Joseph Investments Ltd | Real estate | 2020 |
| Ashikur Jaman Forhad Ltd | Wholesale & retail | 2025 |
| Ashridge and Partners Limited | Administrative & support | 2025 |
| Ashton Farrow Property Ltd | Real estate | 2020 |
| Ashtons Legal LLP | | 2023 |
| Ashtons Legal Trust Corporation Limited | Administrative & support | 2018 |
| Ashwell Construction Limited | Construction | 2018 |
| Asiana Travel Ltd | Administrative & support | 2025 |
| Asitrading Ltd | Wholesale & retail | 2025 |
| ASJ Digital Media Ltd | Information & communication | 2022 |
| ASK Bukki Ltd | Administrative & support | 2020 |
| ASK Calendars Limited | Manufacturing | 2021 |
| ASK Local Limited | Manufacturing | 2021 |
| ASK Online Limited | Manufacturing | 2021 |
| ASK Therapy Ltd | Professional & scientific | 2019 |
| ASK WHY Group Ltd | Professional & scientific | 2022 |
| Askk Homes Ltd | Real estate | 2024 |
| Askncart Ltd | Information & communication | 2023 |
| Asknovation Limited | Professional & scientific | 2024 |
| ASL BSE Limited | Construction | 2004 |
| Aslete Ltd | Information & communication | 2025 |
| ASM 51 Services Ltd | Construction | 2024 |
| Asmo World Ltd | Wholesale & retail | 2025 |
| Aspect Blinds Ltd | Manufacturing | 2014 |
| Aspect Skills Ltd | Professional & scientific | 2014 |
| Aspire Automotive Group Limited | Wholesale & retail | 2024 |
| Aspr Networks Ltd | Arts & recreation | 2025 |
| Asprey Residential Ltd | Real estate | 2025 |
| Aspyre Therapy Solutions Ltd | Health & social care | 2018 |
| Asset Management & Transport Ltd | Transport & logistics | 2025 |
| Assist Marketing Group Limited | Administrative & support | 2018 |
| Association of Health and Wellbeing Coaches CIC | Other services | 2025 |
| Association of Professional Healthcare Analysts CIC | Administrative & support | 2018 |
| Assure Finance Ltd | Other services | 2025 |
| Assured Optimal Care Ltd | Administrative & support | 2023 |
| Assured SIA Training Solutions Ltd | Other services | 2026 |
| Assurity Developments Ltd | Real estate | 2025 |
| Asta Training Limited | Education | 2023 |
| Astar Doctors Ltd | Health & social care | 2023 |
| Astelyx Ltd | Information & communication | 2026 |
| Aster Chase Limited | Professional & scientific | 2022 |
| Asterall Group Ltd | Real estate | 2021 |
| Asteria Business Development Ltd | Real estate | 2012 |
| Astersim Ltd | Information & communication | 2026 |
| Aston Marin Limited | Professional & scientific | 2024 |
| Aston Metrics Ltd | Information & communication | 2026 |
| Aston Mgmt Ltd | Real estate | 2026 |
| Aston Parkes Management Company Limited | Real estate | 2026 |
| Astondock Limited | Education | 2024 |
| Astra Blue Limited | Wholesale & retail | 2025 |
| Astra Property Maintenance Ltd | Construction | 2026 |