| AT Creations Limited | Wholesale & retail | 2016 |
| AT Home London Ltd | Construction | 2021 |
| AT Home London Maintenance Limited | Construction | 2025 |
| Atai Storage Ltd | Transport & logistics | 2019 |
| Atanasov Limited | Construction | 2005 |
| Atanda Group Ltd | Extraterritorial | 2015 |
| ATC General Trading Ltd | Wholesale & retail | 2011 |
| ATE IT Services Ltd | Information & communication | 2026 |
| Atharv Finance Ltd | Financial services | 2025 |
| Athorpe Limited | Construction | 2012 |
| Athwal Constructions Limited | Construction | 2016 |
| Atla Property Limited | Real estate | 2025 |
| Atlantic Freight Limited | Transport & logistics | 2001 |
| Atlantic Notch UK Ltd | Real estate | 2023 |
| Atlas Homes Limited | Construction | 2006 |
| Atlas Living Limited | Construction | 2012 |
| Atlas New Homes Limited | Construction | 2004 |
| Atlas Properties Limited | Construction | 2006 |
| Atlas Residency Limited | Real estate | 2019 |
| Atlas Vertical Ltd | Construction | 2025 |
| Atlasair Ltd | Transport & logistics | 2022 |
| ATO Property Group Ltd | Administrative & support | 2026 |
| Atozbuild Constraction Limited | Construction | 2025 |
| Atrium Trade Limited | Real estate | 2018 |
| ATS Hospitality Limited | Hospitality | 2026 |
| ATS Luxury Interiors Limited | Construction | 2022 |
| ATS Premier Interiors Ltd | Construction | 2013 |
| Attleborough Foods Limited | Manufacturing | 2021 |
| Attraction UK Ltd | Wholesale & retail | 2019 |
| Audio Visual Services Corporation Limited | Professional & scientific | 1973 |
| Augendum Ltd | Wholesale & retail | 2009 |
| Aujla Property Limited | Construction | 2014 |
| AUM Accounting Services Limited | Professional & scientific | 2001 |
| Aura Living Spaces Ltd | Wholesale & retail | 2026 |
| Aureliaa Global Limited | Financial services | 2025 |
| Aurora Couture Ltd | Wholesale & retail | 2025 |
| Aurra London Ltd | Wholesale & retail | 2023 |
| Auto Assure Warranty Ltd | Wholesale & retail | 2026 |
| Auto Dynamics Ltd | Manufacturing | 2011 |
| Auto Point Motors Limited | Wholesale & retail | 2025 |
| Auto Vuego Motors Ltd | Wholesale & retail | 2025 |
| Autofix West London Ltd | Wholesale & retail | 2025 |
| Autolab Solutions Ltd | Manufacturing | 2024 |
| Automatedstorage Ltd | Other services | 2024 |
| Automatedstorage South Mimms Ltd | Transport & logistics | 2024 |
| Automator Limited | Information & communication | 2018 |
| Automotive Consultancy Uxbridge Ltd | Administrative & support | 2023 |
| Autowindz Ltd | Wholesale & retail | 2023 |
| Auxo Commercial Limited | Administrative & support | 1982 |
| Auxo Future Build Limited | Administrative & support | 2010 |
| Auxo Group (Midco) Limited | Financial services | 2021 |
| Auxo Group Holdings Limited | Financial services | 2019 |
| Auxo Services Limited | Administrative & support | 2009 |
| AV Analysis Ltd | Information & communication | 2024 |
| AV Woodsman Limited | Construction | 2014 |
| Avanivk Limited | Professional & scientific | 2018 |
| Avantcore Technologies Ltd | Information & communication | 2022 |
| Avantechsoftware Ltd | Information & communication | 2019 |
| Avay Home Ltd | Real estate | 2024 |
| AVC Live Limited | Professional & scientific | 1985 |
| AVD Limited | Real estate | 2025 |
| Avebury Technologies Limited | Professional & scientific | 2023 |
| Avelo Ltd | Administrative & support | 2026 |
| Avenue Thorn Recruitment Services Ltd | Administrative & support | 2019 |
| Avery Court Management Company (High Wycombe) Limited | Real estate | 1998 |
| Aviation Partnership | | 1995 |
| Aviation Personnel Ltd | Administrative & support | 2018 |
| Aviation Support Limited | Transport & logistics | 1986 |
| Avis & Co UK Limited | Hospitality | 2005 |
| Avit Holdings Limited | Financial services | 2018 |
| AVK I-Care Limited | Health & social care | 2013 |
| AVK Travel Management & Consultancy Ltd | Administrative & support | 2025 |
| AVM Building Services Ltd | Construction | 2019 |
| AVN Consulting Services IT Ltd | Wholesale & retail | 2015 |
| Avni Estates Ltd | Real estate | 2025 |
| Avnimed Limited | Health & social care | 2016 |
| AVS Express Retails Ltd | Wholesale & retail | 2018 |
| AVS Property Estate Ltd | Real estate | 2024 |
| Avsc Europe Limited | Professional & scientific | 1997 |
| Avyaan Investement Group Ltd | Real estate | 2025 |
| AW London Limited | Professional & scientific | 2015 |
| Awad Telecom Innovations Limited | Information & communication | 2018 |
| Awwam Care Ltd | Health & social care | 2025 |
| Awwam Properties Ltd | Real estate | 2025 |
| AX8 Ltd | Administrative & support | 2020 |
| Axiom Education (Edinburgh) Holdings Limited | Financial services | 2006 |
| Axiom Education (Edinburgh) Limited | Real estate | 2006 |
| Axiom Education (Perth & Kinross) Holdings Limited | Financial services | 2005 |
| Axiom Education (Perth & Kinross) Limited | Real estate | 2005 |
| Axiom Networks Limited | Information & communication | 2011 |
| AY House Ltd | Real estate | 2025 |
| Ayaan Kumar Ltd | Hospitality | 2025 |
| Aykki Estates Private Ltd | Real estate | 2026 |
| Ayla Construction Ltd | Construction | 2021 |
| Aylsham Cleaning Services Ltd | Administrative & support | 2026 |
| Ayom Properties Limited | Real estate | 2019 |
| Aytec Global Ltd | Wholesale & retail | 2023 |
| AYU Ayurveda Ltd | Health & social care | 2024 |
| AZ & When Limited | Transport & logistics | 2003 |
| AZ & When Logistics Ltd | Transport & logistics | 2020 |