| Atonement Presence Limited | Information & communication | 2017 |
| Atputhajeyam Wholesalers Ltd | Wholesale & retail | 2026 |
| Atrisa's Properties Ltd | Real estate | 2024 |
| Atrylogy Limited | Wholesale & retail | 2016 |
| ATS House Limited | Real estate | 2023 |
| Attak Performance Limited | Professional & scientific | 2017 |
| Attana Storm Ltd | Wholesale & retail | 2019 |
| Atteres Judaica Ltd | Wholesale & retail | 2022 |
| Attermire Change Solutions Limited | Education | 2014 |
| Attomkeji Ltd | Information & communication | 2022 |
| Atzas Hashem Limited | Financial services | 2022 |
| Audax Initiative Ltd | Wholesale & retail | 2018 |
| Audio Play Research Ltd | Arts & recreation | 2024 |
| Audio Visual Entertainment Limited | Wholesale & retail | 2002 |
| Audiologist Limited | Health & social care | 2018 |
| Auditax (UK) LLP | | 2012 |
| Auditax Limited | Professional & scientific | 2002 |
| Audley Management Company Limited | Construction | 1987 |
| Auebere Ltd | Construction | 2023 |
| Augtronic Limited | Professional & scientific | 2013 |
| August & Forever Ltd | Wholesale & retail | 2025 |
| Augustina's Love Ltd | Manufacturing | 2023 |
| Augustus Mews Management Company Limited | Households | 2004 |
| Aulos Consultancy Limited | Professional & scientific | 2025 |
| AUM Management Limited | Health & social care | 2013 |
| AUM SAI Property Developer Ltd | Construction | 2017 |
| Aumex Group Ltd | Wholesale & retail | 2025 |
| Aumkareshwar Limited | Wholesale & retail | 2023 |
| Aumsai Construction Limited | Construction | 2016 |
| Aumsai UK Limited | Construction | 2019 |
| Aunty Helen's Ltd | Hospitality | 2019 |
| Aunty Perelle's Ltd | Health & social care | 2026 |
| Aunty Perelle's Playgroup Ltd | Health & social care | 2026 |
| Aura (Brazil) Limited | Professional & scientific | 2015 |
| Aura Advisors Limited | Professional & scientific | 2022 |
| Aura Cafe Restaurant Ltd | Hospitality | 2025 |
| Aura Financial LLP | | 2004 |
| AURELE6 Ltd | Wholesale & retail | 2025 |
| Aurelium Group Limited | Construction | 2026 |
| Aureus Advisory Ltd | Professional & scientific | 2026 |
| Aurillium Limited | Professional & scientific | 1991 |
| Aurum Global Limited | Professional & scientific | 2021 |
| Ausa Oceanic LLP | | 2020 |
| Ausa Sahitaj Dryling Ltd | Construction | 2025 |
| Aushi Ltd | Manufacturing | 2012 |
| Auto Authority Ltd | Wholesale & retail | 2023 |
| Auto Best (UK) Ltd | Transport & logistics | 2016 |
| Auto Centrum London Ltd | Wholesale & retail | 2026 |
| Auto M & R Ltd | Wholesale & retail | 2023 |
| Auto Workshop Limited | Wholesale & retail | 2001 |
| Auto Xpress Hire Limited | Extraterritorial | 2010 |
| Autohaus Car Design and Conversion Limited | Other services | 1988 |
| Automatalk LLP | | 2023 |
| Automated Retail Technical Solutions Limited | Administrative & support | 2025 |
| Autonomous (UK) Limited | Administrative & support | 2014 |
| Autonomous Limited | Information & communication | 2001 |
| Autonomous Narrow Frame of Midnight Limited | Information & communication | 2013 |
| Autoxklasseuk Ltd | Wholesale & retail | 2026 |
| Auxiliary Limited | Information & communication | 2012 |
| AV Estates Limited | Real estate | 2021 |
| AV Plumbing & GAS Ltd | Construction | 2017 |
| AVA Prime Construction Ltd | Construction | 2025 |
| Avant & Co Accountants Ltd | Professional & scientific | 2020 |
| Avant Yoga Studio Ltd | Health & social care | 2025 |
| Avantgarde Training Limited | Professional & scientific | 2007 |
| Avanti Business Limited | Professional & scientific | 2018 |
| Avanti Education Limited | Education | 2017 |
| Avanti Foundation Limited | Education | 2014 |
| Aveera Capital II Limited | Other services | 2021 |
| Aveera Capital Limited | Financial services | 2019 |
| Avella Designs Ltd | Wholesale & retail | 2023 |
| Aventa Prestige Limited | Wholesale & retail | 2025 |
| Avenue House Cafe Limited | Hospitality | 2024 |
| Averest Inc Ltd | Professional & scientific | 2012 |
| Avgor Group Ltd | Real estate | 2021 |
| AVI Contracts Limited | Construction | 1998 |
| AVI Interiors Limited | Construction | 2021 |
| Avia Capital Limited | Professional & scientific | 2018 |
| Aviakit Ltd | Wholesale & retail | 2011 |
| Avimett Limited | Construction | 2019 |
| AVK Wholesalers Ltd | Wholesale & retail | 2024 |
| Avlani Ltd | Real estate | 2014 |
| AVM Property Maintenance Ltd | Administrative & support | 2021 |
| AVM Retail Ltd | Wholesale & retail | 2024 |
| AVN Investment Group Ltd | Real estate | 2022 |
| Avocado Developments Limited | Construction | 2007 |
| Avocado Developments Wealdstone Limited | Construction | 2017 |
| Avor Pleaters Limited | Manufacturing | 1965 |
| AVR Joinery Ltd | Manufacturing | 2024 |
| Avraam Ltd | Professional & scientific | 2012 |
| Avraam Property Enterprise Ltd | Real estate | 2015 |
| Avraam Siblings Ltd | Real estate | 2019 |
| Avventura World Limited | Wholesale & retail | 2020 |
| Awareness Investments Limited | Professional & scientific | 1995 |
| Awareness Limited | Health & social care | 2002 |
| Awesome Events Limited | Arts & recreation | 1996 |
| Awesome Grandfather Investments (UK) Limited | Financial services | 2022 |
| Awwadh Property Limited | Real estate | 2024 |
| Axcel Academy Ltd | Education | 2024 |
| Axel Corp Limited | Wholesale & retail | 2023 |