| Atticus Creative Limited | Administrative & support | 2008 |
| Atty.Kiss Ltd | Transport & logistics | 2019 |
| Atwick Enterprise Ltd | Wholesale & retail | 2026 |
| ATZ Group Limited | Construction | 2018 |
| ATZ Group Property Limited | Real estate | 2026 |
| AU Plus Ltd | Extraterritorial | 2016 |
| Auckland Court Management Limited | Households | 2005 |
| Auckley Pre-School Limited | Education | 2015 |
| Auckley School | Education | 2011 |
| Audiken Medical Limited | Administrative & support | 2023 |
| Audit Projects Limited | Professional & scientific | 2007 |
| AUP Store Ltd | Wholesale & retail | 2018 |
| Aura (Bawtry) Ltd | Other services | 2026 |
| Aura Management Ltd | Arts & recreation | 2022 |
| Aura Metal Trading Ltd | Wholesale & retail | 2025 |
| Aura Pubs Limited | Hospitality | 2017 |
| Aura Purchasing Ltd | Professional & scientific | 2024 |
| Auralith Capital Ltd | Extraterritorial | 2026 |
| Aurelia Health Partners Ltd | Extraterritorial | 2026 |
| Aurelianvana Limited | Transport & logistics | 2017 |
| Aurevale Limited | Extraterritorial | 2026 |
| Aurevanta Ltd | Wholesale & retail | 2025 |
| Auricule Limited | Administrative & support | 2021 |
| Auriel Majumdar Limited | Professional & scientific | 2013 |
| Aurora Link Services Ltd | Extraterritorial | 2025 |
| Austech Apps Limited | Information & communication | 2023 |
| Austerfield Acquisitions Ltd | Real estate | 2024 |
| Austerfield Study Centre Limited | Education | 2013 |
| Austria Holdings Investment Inc Ltd | Professional & scientific | 2016 |
| Authentic Care Services Limited | Health & social care | 2006 |
| Authentica Consulting Ltd | Professional & scientific | 2024 |
| Autism Diagnostics Healthcare Ltd | Health & social care | 2024 |
| Autism Plus Limited | Health & social care | 1987 |
| Auto Electrical Conversions & Repair Ltd | Construction | 2023 |
| Auto FIX Doncaster Ltd | Wholesale & retail | 2025 |
| Auto Pack Solutions Ltd | Administrative & support | 2025 |
| Auto Service Garage Ltd | Wholesale & retail | 2018 |
| Auto Technics Ltd | Wholesale & retail | 2009 |
| Autobedrijf Suierveld LLP | | 2022 |
| Autocar Logistics (IRL) Limited | Transport & logistics | 2008 |
| Autoclarity Ltd | Professional & scientific | 2018 |
| Autofinish Ltd | Wholesale & retail | 2000 |
| Autofit(Doncaster) Limited | Wholesale & retail | 2018 |
| Autojumble Limited | Wholesale & retail | 2019 |
| Automated Analytics Limited | Administrative & support | 2013 |
| Automatic Entry Solutions Limited | Extraterritorial | 2013 |
| Automation Design Services Ltd | Information & communication | 2012 |
| Automodus Ltd | Wholesale & retail | 2012 |
| Automotion Studio Ltd | Information & communication | 2019 |
| Automotive Business Results Ltd | Professional & scientific | 2014 |
| Automotive Leisure Services Limited | Wholesale & retail | 2018 |
| Automotive Speed Ltd | Water & waste | 2025 |
| Autopack Motor Trade Factors Limited | Wholesale & retail | 1978 |
| Autopaint Solutions (UK) Limited | Wholesale & retail | 2009 |
| Autopak Solutions Limited | Manufacturing | 2019 |
| Autoshine Balby Ltd | Wholesale & retail | 2017 |
| Autospec Vehicle Mechanics Ltd | Transport & logistics | 2023 |
| Autotekdirect Limited | Wholesale & retail | 2020 |
| Autototal Solutions Ltd | Transport & logistics | 2019 |
| Autotrade Yorkshire Limited | Wholesale & retail | 2025 |
| Auxilium Plumbing Limited | Construction | 2018 |
| Auxillium Civils Limited | Professional & scientific | 2019 |
| AV Accessories Limited | Wholesale & retail | 2009 |
| AV Pizza Limited | Hospitality | 2019 |
| Avaia Care Ltd | Health & social care | 2025 |
| Avakuk Ltd | Wholesale & retail | 2025 |
| Avallo Homes Ltd | Construction | 2020 |
| Avalon FS Ltd | Financial services | 2020 |
| Avatar S N Ltd | Wholesale & retail | 2018 |
| AVB Depot Services Ltd | Transport & logistics | 2026 |
| Avcarini Ltd | Real estate | 2022 |
| Aveita Holdings Ltd | Wholesale & retail | 2002 |
| Aveita Ltd | Wholesale & retail | 2023 |
| Aventurin Capital Ltd | Real estate | 2018 |
| Avenue Accountancy Services Ltd | Professional & scientific | 2007 |
| Avenue Bars & Clubs Limited | Hospitality | 2025 |
| Avenue Sixty 7 Ltd | Information & communication | 2008 |
| Avery Plus Care Ltd | Health & social care | 2023 |
| Avery Plus Consult Ltd | Professional & scientific | 2020 |
| Avery Plus Investments Ltd | Households | 2026 |
| Averyne Limited | Wholesale & retail | 2026 |
| Avesta Properties Limited | Real estate | 2021 |
| Avian Breeding Limited | Agriculture & fishing | 2018 |
| AVL Event Production Ltd | Administrative & support | 2026 |
| Avneet Stores Ltd | Wholesale & retail | 2023 |
| Avocet Developments Ltd | Real estate | 2020 |
| Avon Roofing Yorkshire Ltd | Construction | 2019 |
| Avram Marketing Ltd | Professional & scientific | 2024 |
| Avtech Security Installations LLP | | 2022 |
| Avvenente Ltd | Households | 2024 |
| AW & VW Holdings Limited | Financial services | 2020 |
| AW Properties Holdings Limited | Real estate | 2023 |
| AW2 Estates Ltd | Real estate | 2026 |
| Awaking Giants Ltd | Construction | 2019 |
| Awaking Preloved Ltd | Wholesale & retail | 2021 |
| AWB Truckmixers Limited | Transport & logistics | 2001 |
| AWD Decorating Limited | Construction | 2025 |
| AWG Contractors Ltd | Construction | 2019 |
| AWG Services Limited | Professional & scientific | 2019 |
| AWI Ltd | Professional & scientific | 2024 |