| Aris Group Limited | Arts & recreation | 2025 |
| Arisdale Avenue Thurrock Management Limited | Households | 2010 |
| Arisdale Place (South Ockendon) Management Company Limited | Households | 2013 |
| Arisee Care Ltd | Health & social care | 2024 |
| ARK Transport Services Ltd | Transport & logistics | 2024 |
| Arkle Electronic Systems Limited | Information & communication | 2008 |
| Arkle Trading Group Limited | Financial services | 2014 |
| Arle Cleaning Services Limited | Administrative & support | 2025 |
| Arnbri Limited | Information & communication | 2022 |
| Arom Real Estate Limited | Real estate | 2024 |
| Arron Cofey Scardifield Modeste Ltd | Extraterritorial | 2024 |
| Art of Hair & Beauty Ltd | Other services | 2019 |
| Art Republic Limited | Financial services | 2025 |
| Artemida Pharma Limited | Professional & scientific | 2014 |
| Arthur Estate Limited | Real estate | 2021 |
| Artion Ltd | Construction | 2009 |
| Artista Design Limited | Administrative & support | 2012 |
| AS Healthcare Improvement Ltd | Professional & scientific | 2021 |
| AS-RM1-PROPERTY Limited | Real estate | 2024 |
| As-Sure Physio Ltd | Health & social care | 2018 |
| AS2EDUCATE Ltd | Education | 2021 |
| ASA Travel Services Ltd | Transport & logistics | 2019 |
| ASA UK Services Limited | Other services | 2025 |
| Asak Properties Limited | Real estate | 2019 |
| Asap Architectural Ltd | Manufacturing | 2025 |
| Asap Stevenage Ltd | Manufacturing | 2017 |
| ASB Property Services (UK) Limited | Construction | 2009 |
| ASC Electrical Contractor Limited | Construction | 2015 |
| Ascend Gym Ltd | Arts & recreation | 2025 |
| Ascendia Consults Limited | Professional & scientific | 2025 |
| Ascent 4520 Limited | Real estate | 2026 |
| Ascott PH Services Limited | Construction | 2004 |
| ASG Construction Services Limited | Construction | 2009 |
| ASH Generations Limited | Real estate | 2018 |
| ASH House Management Company Limited | Households | 2002 |
| ASH Shah Ltd | Health & social care | 2016 |
| Asha Pharma Ltd | Health & social care | 2023 |
| Ashaycara Limited | Health & social care | 2018 |
| Ashberg Consulting Ltd | Professional & scientific | 2009 |
| Ashbourne 1843 Ltd | Information & communication | 2026 |
| Ashby Fire Safety Services Limited | Professional & scientific | 2017 |
| Ashby Property Investment Ltd | Real estate | 2021 |
| Ashcroft Management (Primett Road) Limited | Households | 2007 |
| Ashden Group Limited | Other services | 2015 |
| Ashley Coleman Property Limited | Real estate | 2017 |
| Ashley White Editing Ltd | Information & communication | 2016 |
| Ashter Homes Limited | Real estate | 2018 |
| Ashton George Ltd | Arts & recreation | 2022 |
| Ashtons Property Services Ltd | Construction | 2026 |
| Ashtons Property Solutions LLP | | 2024 |
| Ashtons Services Holdings Ltd | Financial services | 2024 |
| Asif Faizy GP Limited | Health & social care | 2015 |
| ASK Homeowner Ltd | Real estate | 2023 |
| Aski-Green Limited | Health & social care | 2016 |
| Aski-Green Property Ltd | Real estate | 2019 |
| ASM Pets Ltd | Wholesale & retail | 2021 |
| Asmj Ltd | Real estate | 2026 |
| Asolution (UK) Limited | Information & communication | 2009 |
| Aspect Marketing Ltd | Professional & scientific | 2017 |
| Aspinall Estates Ltd | Construction | 2019 |
| Aspire Heights Limited | Health & social care | 2025 |
| Aspyrian Ltd | Extraterritorial | 2018 |
| ASR Electrical Services Limited | Construction | 2016 |
| Asser Ltd | Administrative & support | 2016 |
| Assetia Group Ltd | Real estate | 2024 |
| Assetta Calvert Mews Limited | Construction | 2020 |
| Assetta Consult Limited | Other services | 2018 |
| Assetta Ltd | Real estate | 2016 |
| Assetta SJM Ltd | Real estate | 2025 |
| Associated British Bulbs | Wholesale & retail | 1963 |
| Assurance Recruitment Agency Limited | Administrative & support | 2017 |
| Assured Base Ltd | Real estate | 2023 |
| Assured Network Solutions Limited | Information & communication | 2021 |
| Assynt Corporate Finance Limited | Professional & scientific | 2013 |
| AST Authors Limited | Information & communication | 2001 |
| AST Holidays Ltd | Administrative & support | 2026 |
| AST Property Experts Ltd | Construction | 2026 |
| Astech Electrical Contractors Limited | Energy | 2014 |
| Asteri Enterprise Limited | Real estate | 2012 |
| Aston Blake Renewable Energy Ltd | Professional & scientific | 2024 |
| Aston Blake Resources Ltd | Professional & scientific | 2026 |
| Aston Blake Services Ltd | Professional & scientific | 2023 |
| Aston Brook Estates Ltd | Real estate | 2021 |
| Aston Clinton Scientific Limited | Health & social care | 1997 |
| Aston Group Holdings Limited | Financial services | 2018 |
| Aston Media Productions Limited | Information & communication | 2017 |
| Aston Vale Management Company Limited | Households | 2013 |
| Astonedge Properties Limited | Real estate | 2015 |
| Astoria Land Limited | Real estate | 2018 |
| Astute Distribution Limited | Wholesale & retail | 2017 |
| Astute Electronics Limited | Wholesale & retail | 1988 |
| Atam GAS Ltd | Construction | 2024 |
| ATG Aerospace Limited | Professional & scientific | 2011 |
| Athena Enterprises (UK) Limited | Financial services | 2008 |
| ATK Engineering Ltd | Professional & scientific | 2021 |
| Atkinson Medical Limited | Health & social care | 2026 |
| Atkinson's Homeware Limited | Wholesale & retail | 2018 |
| Atlantic Construction & Design Services Limited | Administrative & support | 2005 |
| Atlantic Engineering Services Ltd | Construction | 2026 |
| Atlantic Gentrade Limited | Wholesale & retail | 2013 |