| Amberley Ltd | Professional & scientific | 2022 |
| Ambermill Limited | Households | 2008 |
| Ambiance Securities Limited | Real estate | 1982 |
| Ambience Control Ltd | Real estate | 1995 |
| Ambitious Learning Company Limited | Administrative & support | 2017 |
| Amcro Building Limited | Construction | 2017 |
| Ameenovisual Limited | Information & communication | 2019 |
| Amelia Griggs Limited | Professional & scientific | 2019 |
| American Golden Nails Ltd | Other services | 2017 |
| Amherst Systems Engineering Ltd | Professional & scientific | 2023 |
| Amir Orpington Ltd | Wholesale & retail | 2025 |
| AMK Financial Limited | Administrative & support | 2019 |
| AMM CAR3ON Ltd | Other services | 2024 |
| Ammano Care Ltd | Health & social care | 2015 |
| Ammtech Limited | Construction | 2015 |
| Amora Collective Ltd | Manufacturing | 2025 |
| Amplifirm Ltd | Information & communication | 2024 |
| Ampower Consulting Ltd | Real estate | 2012 |
| Amptech Energy Solutions Limited | Professional & scientific | 2019 |
| AMS Building Contractors Ltd | Construction | 2018 |
| AMS Express Limited | Transport & logistics | 2024 |
| AMT Healthcare Limited | Professional & scientific | 2015 |
| AMY Rowlinson Limited | Administrative & support | 2020 |
| ANA Leaf Foundation | Administrative & support | 2009 |
| Anarosa Global Ltd | Other services | 2014 |
| Anastasia's Pantry Ltd | Manufacturing | 2021 |
| Anchor Holds Healthcare Limited | Health & social care | 2026 |
| Anchu Holdings Ltd | Real estate | 2021 |
| Anda Carpentry&Joinery Ltd | Construction | 2025 |
| Andara Ltd | Administrative & support | 2017 |
| Andover Express Ltd | Wholesale & retail | 2023 |
| Andrich Limited | Professional & scientific | 2008 |
| Andy Baker Associates Limited | Administrative & support | 2015 |
| Andy Fordham Creative Limited | Information & communication | 2023 |
| Andy the Fish MAN Limited | Other services | 2019 |
| Andyc Solutions Limited | Construction | 2016 |
| Anel Ltd | Real estate | 2011 |
| Anetkaproperties Ltd | Real estate | 2021 |
| Angel Aesthetics Tattoo Ltd | Arts & recreation | 2023 |
| Angel and Friends | Health & social care | 2017 |
| Angel Face Aesthetics London Ltd | Other services | 2025 |
| Angelic Health Care and Services Ltd | Health & social care | 2021 |
| Angerstein Estates (Plymouth) Limited | Real estate | 1999 |
| Angerstein Estates Limited | Real estate | 1970 |
| Angerstein Residential Limited | Real estate | 2001 |
| Angier & Frowde Limited | Construction | 1947 |
| Anglian Energy Solutions Ltd | Information & communication | 2005 |
| Anieta Limited | Real estate | 2021 |
| Anismi Ltd | Real estate | 2024 |
| Anjou Campbell Ltd | Public administration | 2023 |
| Anju Bansal Consultancy Ltd | Education | 2021 |
| ANM Services Ltd | Real estate | 2022 |
| ANN Classic Contracts Ltd | Hospitality | 2021 |
| Annex (Films) Limited (the) | Information & communication | 1973 |
| Annievianne Ltd | Administrative & support | 2017 |
| Anoop Anugraha Ltd | Other services | 2022 |
| ANP Medical Ltd | Health & social care | 2023 |
| Ansah Templeton Chambers Limited | Extraterritorial | 2020 |
| Ansion Limited | Extraterritorial | 2016 |
| Ansion Properties Limited | Real estate | 2016 |
| Antares Wellbeing Ltd | Health & social care | 2018 |
| Anthony Accounting & Payroll Services Ltd | Administrative & support | 2017 |
| Anthowise Ltd | Information & communication | 2025 |
| Antic Animation Limited | Professional & scientific | 2008 |
| Antony Royce Consultancy Limited | Professional & scientific | 2015 |
| Antservicegroup Ltd | Construction | 2016 |
| Aoca (UK) Limited | Professional & scientific | 2017 |
| AOS Accountants Ltd | Professional & scientific | 2024 |
| AP FX Management Limited | Professional & scientific | 2022 |
| Apecks Limited | Financial services | 2025 |
| Apex & Fjord Limited | Wholesale & retail | 2025 |
| Apex Electrical Contractors Ltd | Construction | 2011 |
| Apex Sealants Ltd | Construction | 2023 |
| Apnorris Ltd | Information & communication | 2024 |
| Apollo Autos Limited | Wholesale & retail | 2003 |
| Appear Natural Limited | Other services | 2015 |
| Appflux Labs Ltd | Information & communication | 2025 |
| Appiah-Kubi Properties Ltd | Real estate | 2019 |
| April Blinds Ltd | Wholesale & retail | 2016 |
| Apro Scaffolding Ltd | Construction | 2015 |
| APS Tech Solutions Limited | Information & communication | 2015 |
| APS Transport Ltd | Transport & logistics | 2025 |
| AQT Beauty Ltd | Professional & scientific | 2026 |
| Aqua Smart Water Treatment Ltd | Water & waste | 2019 |
| Aquanero Limited | Construction | 2011 |
| Aquapulse Intelligence Limited | Professional & scientific | 2025 |
| Aquillo Chartering Limited | Transport & logistics | 2022 |
| Aquis Mechanical Ltd | Construction | 2023 |
| Aquis Properties Ltd | Real estate | 2025 |
| AR Fitness & Mentoring Limited | Professional & scientific | 2024 |
| Aran (High Wycombe) Limited | Real estate | 2007 |
| Aran Investments Limited | Real estate | 2006 |
| Aran Orpington Limited | Real estate | 2022 |
| Arbee Ltd | Professional & scientific | 2025 |
| Arbofari Limited | Construction | 2024 |
| Arcadia Rose Design Ltd | Professional & scientific | 2026 |
| Archetile Ltd | Construction | 2022 |
| Archetype Systems Limited | Information & communication | 2026 |
| Architecturall Development Ltd | Real estate | 2016 |
| Architecturall Ltd | Construction | 2010 |