| Angela Cade Architect Limited | Professional & scientific | 2016 |
| Anglesey Holdings Limited | Professional & scientific | 2004 |
| Animal Think Tank Community Interest Company | Other services | 2019 |
| Anomalocaris Ltd | Professional & scientific | 2022 |
| Anst Ltd | Construction | 2018 |
| Antalya Barbers Limited | Other services | 2022 |
| Ante Mors Ltd | Manufacturing | 2023 |
| Anuar Ltd | Hospitality | 2025 |
| Anyhow Ltd | Professional & scientific | 2012 |
| Apertura Studios Ltd | Professional & scientific | 2025 |
| Aplt Interests Limited | Health & social care | 2016 |
| APM Consultancy Services Ltd | Professional & scientific | 2010 |
| Apocalypse Pictures Limited | Information & communication | 2012 |
| Apollo Behaviour Support Team Limited | Education | 2025 |
| Appkraft Limited | Professional & scientific | 2014 |
| Appledore Montessori Ltd | Health & social care | 2021 |
| Applegrove London Ltd | Real estate | 2016 |
| Appletree Carpentry & Joinery Ltd | Construction | 2003 |
| Approved Inspectors Limited | Construction | 2008 |
| Apricot Electronics Limited | Information & communication | 2023 |
| Apricot Homes Limited | Construction | 2023 |
| Apricot Whirl Ltd. | Wholesale & retail | 2014 |
| APS Professional Consultancy Ltd | Professional & scientific | 2015 |
| Apsv (Avant) Ltd | Wholesale & retail | 2023 |
| Aptc Ltd | Professional & scientific | 2025 |
| Aqua Engineering Solutions Limited | Water & waste | 2000 |
| Aquajade Bathrooms Limited | Construction | 2008 |
| Aquamajik Company Limited | Hospitality | 2017 |
| Aquasupply Limited | Hospitality | 1996 |
| Aqueduct Recruitment Ltd. | Administrative & support | 2022 |
| Arabesque School of Performing Arts Limited | Arts & recreation | 2024 |
| Arabic Music Academy in London Ltd. | Information & communication | 2017 |
| Arajpa Limited | Real estate | 2020 |
| Aramoana Ltd | Real estate | 2021 |
| ARC Lancaster Limited | Manufacturing | 2010 |
| ARC Media Group Limited | Other services | 2025 |
| Arc-Rite Welding & Safety Limited | Wholesale & retail | 1991 |
| Archers @ Red Bank Farm Limited | Agriculture & fishing | 2017 |
| Archihive Studios Ltd | Professional & scientific | 2020 |
| Architeuthis Locum Services Ltd | Professional & scientific | 2013 |
| Archive Films Limited | Information & communication | 2018 |
| Archway Enterprises Limited | Extraterritorial | 2006 |
| Arden Close a RTM Company Limited | Households | 2025 |
| Arden Close B RTM Company Limited | Households | 2025 |
| Arden Close C RTM Company Limited | Households | 2025 |
| Arden Close D RTM Company Limited | Households | 2025 |
| Arden Close E RTM Company Limited | Households | 2025 |
| Arden Close F RTM Company Limited | Households | 2025 |
| Arden Close G RTM Company Limited | Households | 2025 |
| Arden Close H RTM Company Limited | Households | 2025 |
| Ardent LM Ltd | Manufacturing | 2025 |
| Argus Information Security Limited | Information & communication | 2017 |
| Argyll Management Consulting Ltd | Professional & scientific | 2013 |
| ARH Accountancy & Business Support Limited | Professional & scientific | 2013 |
| Arietis Solutions Ltd | Information & communication | 2016 |
| ARK Care Group Limited | Health & social care | 2025 |
| ARK Consultants UK Ltd | Wholesale & retail | 2002 |
| Arks Technologies Limited | Information & communication | 2011 |
| Armiland Productions Ltd | Information & communication | 2023 |
| Armitage Premium Collection Ltd | Real estate | 2026 |
| Armitstead Barnett LLP | | 2009 |
| Armstrong Speech and Drama Ltd | Arts & recreation | 2021 |
| Arna Wood Management Company Limited | Households | 2004 |
| Arnside Boiler Care Limited | Construction | 2023 |
| Aroma Chef Lancaster Ltd | Hospitality | 2024 |
| Art of Regeneration Limited | Professional & scientific | 2007 |
| Artists in Motion School of Dance Limited | Arts & recreation | 2024 |
| Arun Real Estate Ltd | Real estate | 2024 |
| Aryadya Ltd | Health & social care | 2018 |
| AS Marketing Consultancy Limited | Professional & scientific | 2024 |
| AS Social Work Solutions Limited | Health & social care | 2017 |
| Ascentis | Education | 2009 |
| Asghar & Rizvi Holdings Limited | Real estate | 2025 |
| Ashleigh Estate Holdings Limited | Real estate | 2025 |
| Ashmoor Health Care Limited | Health & social care | 2002 |
| Ashton Coach House Management Limited | Households | 2010 |
| Ashton FS Limited | Professional & scientific | 2014 |
| Ashton Golf and Leisure Limited | Hospitality | 2025 |
| Ashton Golf Centre Limited | Arts & recreation | 2019 |
| Ashwood & Stone Ltd | Real estate | 2021 |
| ASK Insurance Services Limited | Financial services | 2014 |
| Askam Civil Engineering Limited | Construction | 1997 |
| Askam Holdings Limited | Other services | 2015 |
| Askam Plant Limited | Administrative & support | 2015 |
| Askew Property & Lettings Ltd | Real estate | 2022 |
| Asma Health Limited | Health & social care | 2025 |
| Aspen Property Group Limited | Real estate | 2025 |
| Aspire Building & Maintenance NW Limited | Construction | 2025 |
| Aspire Dance Bolton Limited | Arts & recreation | 2024 |
| Aspire Gymnastics Limited | Arts & recreation | 2022 |
| Aspire School of Dance Limited | Arts & recreation | 2019 |
| Asquith Development Project Management Limited | Professional & scientific | 2002 |
| Asset Snap Ltd | Information & communication | 2025 |
| Assi 2 Limited | Real estate | 2022 |
| Assi Holdings Limited | Real estate | 2020 |
| Association of Consumer Support Organisations Ltd | Other services | 2019 |
| Astounded Fireworks Limited | Wholesale & retail | 2017 |
| ASW Private Ltd | Real estate | 2017 |
| Atelier Deux Ltd | Professional & scientific | 2007 |
| Athena Concept Ltd | Professional & scientific | 2019 |