| Aspire Independent Support Community Interest Company | Health & social care | 2017 |
| Aspire PC Limited | Health & social care | 2009 |
| ASPIRE1 Group Ltd | Arts & recreation | 2026 |
| Aspiring Communities Sheffield Limited | Health & social care | 2013 |
| Aspiring Edge Ltd | Professional & scientific | 2025 |
| Asplin Works Limited | Real estate | 2023 |
| Asqab Properties Ltd | Real estate | 2024 |
| Asquith Property Ltd | Real estate | 2024 |
| ASR Academy Ltd | Administrative & support | 2006 |
| Asrconsult Ltd | Information & communication | 2021 |
| Assa Abloy Entrance Systems Ltd | Manufacturing | 1967 |
| Assaaf Ltd | Real estate | 2024 |
| Assb Limited | Transport & logistics | 2025 |
| Assembly GTM Ltd | Information & communication | 2025 |
| Assertive Health Care Limited | Health & social care | 2021 |
| Assess Protection and Properties Limited | Financial services | 2018 |
| Asset Building Consultancy Limited | Professional & scientific | 2014 |
| Asset Collective Ltd | Real estate | 2023 |
| Asset Design Ltd | Professional & scientific | 2020 |
| Asset Go Solutions Ltd | Information & communication | 2020 |
| Asset Management MP Limited | Real estate | 2026 |
| ASSET27 Limited | Information & communication | 2016 |
| Assetminder (Operations) Limited | Information & communication | 2024 |
| Assetminder Limited | Information & communication | 2024 |
| Assist Healthcare Ltd | Health & social care | 2025 |
| Assix Limited | Construction | 2016 |
| Associate Development Solutions Ltd | Professional & scientific | 2011 |
| Associated Polymer Services Group Ltd | Mining & quarrying | 2024 |
| Associated Polymer Services Limited | Mining & quarrying | 1995 |
| Associated Rental Investments Limited | Real estate | 2023 |
| Associated Therapy Services Limited | Health & social care | 2001 |
| Association for the Study of Animal Behaviour Limited | Professional & scientific | 1974 |
| Asspire Fitness Ltd | Education | 2025 |
| Assured Guide Ltd | Professional & scientific | 2025 |
| Assured Homes Group Ltd | Real estate | 2019 |
| Assured Homes Investments Ltd | Real estate | 2020 |
| Assured Productions Limited | Arts & recreation | 2010 |
| Assured Rigging Limited | Construction | 2014 |
| Assured Vehicle Movements Ltd | Transport & logistics | 2022 |
| Astafar Ltd | Real estate | 2020 |
| Astel Systems UK Ltd | Information & communication | 2017 |
| Aster Pharm Ltd | Health & social care | 2022 |
| Asteria Press LLP | | 2023 |
| Astley Park (NO. 1) Management Company Limited | Households | 2008 |
| Astley Park (NO.2) Management Company Limited | Households | 2008 |
| Aston Community Education Trust | Education | 2011 |
| Aston Laser Services Limited | Manufacturing | 2015 |
| Aston Meadows (Management Company) Limited | Households | 2025 |
| Aston Meadows Limited | Construction | 2014 |
| Aston Park Fisheries (Sheffield) Limited | Financial services | 2006 |
| Aston Park Fisheries Limited | Agriculture & fishing | 2002 |
| Aston Pizza Ltd | Hospitality | 2023 |
| Aston Prestige Motors Ltd | Wholesale & retail | 2025 |
| Aston Scaffolding (UK) Limited | Construction | 2001 |
| Aston Spring Farm Limited | Arts & recreation | 2014 |
| Aston Tyres & Motor Services Limited | Wholesale & retail | 2021 |
| Astora Fragrances Ltd | Wholesale & retail | 2026 |
| Astrea Academy Trust | Education | 2015 |
| Astrid Architects Limited | Professional & scientific | 2018 |
| Astro Blossom UK Ltd | Professional & scientific | 2025 |
| Astro Pizza Limited | Hospitality | 2019 |
| Astronomica Ltd | Wholesale & retail | 2023 |
| Astrum (UK) Limited | Extraterritorial | 2010 |
| Astryx Group Ltd | Real estate | 2025 |
| ASTUD4U Limited | Wholesale & retail | 2023 |
| Asugar Limited | Construction | 2016 |
| Asuo Collective CIC | Education | 2026 |
| Asuoonline Healthcare Limited | Health & social care | 2016 |
| ASV Trading Ltd | Wholesale & retail | 2020 |
| Asyah Developers Ltd | Real estate | 2021 |
| AT Consultants Limited | Professional & scientific | 2023 |
| AT Dusk Ltd | Wholesale & retail | 2025 |
| AT Last Limited | Professional & scientific | 2010 |
| AT Perfect Move Ltd | Transport & logistics | 2016 |
| At&Ct Jewellery Ltd | Manufacturing | 2017 |
| At-Tawheed Limited | Administrative & support | 2018 |
| ATA Seafood Limited | Hospitality | 2016 |
| Atacamite Clearances Ltd | Water & waste | 2025 |
| Ataji Holdings Ltd | Financial services | 2025 |
| ATB Rider Training Ltd | Education | 2021 |
| ATC Bars Limited | Hospitality | 2023 |
| Atcs Consulting Ltd | Information & communication | 2023 |
| Atesta Limited | Professional & scientific | 2016 |
| Atgconsultng Limited | Health & social care | 2024 |
| Athelstanone PTY Ltd | Information & communication | 2022 |
| Athena Response Ltd | Administrative & support | 2026 |
| Athena Solid Surfaces Ltd | Construction | 2025 |
| Athena Venture Capital Limited | Financial services | 2022 |
| Atherley Limited | Manufacturing | 2023 |
| Atherton Neuropsychology Consultancy Ltd | Health & social care | 2021 |
| Athi Properties Limited | Real estate | 2012 |
| Athivarun Ltd | Wholesale & retail | 2024 |
| Athlete Management International Limited | Arts & recreation | 2010 |
| Athletic Artist Ltd | Education | 2022 |
| Atholl Commercial Services Ltd | Professional & scientific | 2003 |
| Athona Research Ltd | Health & social care | 2025 |
| ATI Consultants Limited | Professional & scientific | 2025 |
| Atina Solutions Limited | Construction | 2002 |
| Atkey Holdings Limited | Financial services | 2017 |
| Atkey Solutions Limited | Professional & scientific | 2000 |