| Artclimate Ltd | Construction | 2025 |
| Arteck Fire and Security Ltd | Administrative & support | 2023 |
| Artha Properties Limited | Real estate | 2025 |
| Artic Training Limited | Education | 2014 |
| Arties Designs Ltd | Wholesale & retail | 2024 |
| Artis Auto Limited | Manufacturing | 2012 |
| Artm Drylining Ltd | Construction | 2017 |
| Arts Outburst Limited | Arts & recreation | 2005 |
| Artur Interiors Ltd | Manufacturing | 2025 |
| Arvebo Trans Ltd | Transport & logistics | 2018 |
| Arwas Properties Ltd | Real estate | 2026 |
| Aryan ENT Ltd | Real estate | 2020 |
| Arym Ltd | Information & communication | 2023 |
| Arzaf Coaching Consultancy & Training Ltd | Other services | 2018 |
| Arzaf Real Estate Limited | Real estate | 2017 |
| AS & KD Building Services Ltd | Construction | 2022 |
| AS Commercial Solutions Ltd | Construction | 2025 |
| Asante Trade Ltd | Real estate | 2018 |
| Asbestos Consultants Europe Limited | Construction | 2008 |
| Asbestos Surveys Essex Limited | Construction | 2012 |
| Ascend Surveying and Property Ltd | Professional & scientific | 2025 |
| Ascendly Career Consulting Ltd | Administrative & support | 2026 |
| Ascop UK Ltd | Professional & scientific | 2010 |
| ASG Media Limited | Professional & scientific | 2015 |
| ASH Car Bodyshop Ltd | Wholesale & retail | 2025 |
| ASH Groundworks & Civils Ltd | Construction | 2025 |
| ASH Hairline Ltd | Other services | 2024 |
| ASH Site Services Limited | Construction | 2022 |
| Ashah Restaurants Ltd | Hospitality | 2025 |
| Ashe Business Consulting Ltd | Manufacturing | 2017 |
| Ashgrove Mortgages Ltd | Financial services | 2013 |
| Ashlands Management Company Limited | Households | 1974 |
| Ashley Bennett Ltd | Real estate | 2015 |
| Ashlist Construction Ltd | Construction | 2016 |
| Ashton Design Company Limited | Professional & scientific | 1994 |
| Ashtop Medical Consulting Services Ltd | Health & social care | 2017 |
| ASK 4 Accounting Ltd | Professional & scientific | 2023 |
| ASK Business Solutions Limited | Other services | 2002 |
| ASK Kleen Parlour Limited | Other services | 2021 |
| ASO Transport Ltd | Construction | 2025 |
| Aspire Traders Ltd | Wholesale & retail | 2025 |
| Asset Streamline Ltd | Information & communication | 2015 |
| Assiduous Consultancy Solution Limited | Other services | 2016 |
| Associated Waste Group Ltd | Other services | 2007 |
| Associated Waste Land Management Ltd | Other services | 2007 |
| Assu Ltd | Administrative & support | 2025 |
| ASSURED4LIFE Care Limited | Administrative & support | 2020 |
| Assurestor Limited | Information & communication | 2012 |
| Astana Holding Ltd | Real estate | 2016 |
| Aston Reader Properties Ltd | Real estate | 2021 |
| Aswin (UK) Management Limited | Wholesale & retail | 2001 |
| AT Technicians Ltd | Wholesale & retail | 2011 |
| At&At Logistic Solutions Limited | Transport & logistics | 2024 |
| Atcr Limited | Education | 2016 |
| Ates International Limited | Wholesale & retail | 2021 |
| Atherfold Film Services Limited | Professional & scientific | 2010 |
| Athlete Sportal Africa Ltd | Education | 2025 |
| ATI Property Limited | Real estate | 2024 |
| Atiad Properties Ltd | Real estate | 2021 |
| Atilla Ltd | Administrative & support | 2016 |
| Atiph Limited | Administrative & support | 2025 |
| Atlant Capital Group Ltd | Manufacturing | 2022 |
| Atlas Loading Ltd | Transport & logistics | 2024 |
| Atlas Repairs Limited | Wholesale & retail | 1998 |
| Atlas Specialist Vehicles Ltd | Wholesale & retail | 2004 |
| ATN Properties Ltd | Real estate | 2019 |
| Atnm Realty Limited | Households | 2023 |
| ATS Drivers Ltd | Transport & logistics | 2015 |
| ATS Netconsulting Limited | Information & communication | 2018 |
| ATS Transport Ltd | Transport & logistics | 2014 |
| Attaina Limited | Professional & scientific | 2015 |
| Attila Balazs Ltd | Transport & logistics | 2013 |
| Attwood Property Services Limited | Real estate | 2013 |
| ATV Recruitment Ltd | Transport & logistics | 2024 |
| Auditorium Seating Services Ltd | Construction | 2018 |
| Auranest Ltd | Wholesale & retail | 2025 |
| Aurum Business Solutions Ltd | Professional & scientific | 2016 |
| Aurèlia Bloom Ltd | Other services | 2025 |
| Austin Stevens Ltd | Other services | 2015 |
| Authentic New Apostolate Church Ltd | Other services | 2023 |
| Authentic New Apostolate Church UK & Ireland Ltd | Other services | 2026 |
| Authoritty Ltd | Information & communication | 2026 |
| Autland Global Ltd | Wholesale & retail | 2019 |
| Auto Assist 247 Limited Limited | Wholesale & retail | 2025 |
| Auto Second Limited | Professional & scientific | 2020 |
| Autocourier Ltd | Wholesale & retail | 2018 |
| Autolegenduk Ltd | Wholesale & retail | 2015 |
| Automate Artificial Intelligence Limited | Information & communication | 2025 |
| Automatic Training Limited | Education | 2014 |
| Autotechspray Limited | Wholesale & retail | 2024 |
| Autrac Facilities Ltd | Administrative & support | 2013 |
| AV Construction Private Ltd | Construction | 2023 |
| AV Electrical Ltd | Construction | 2018 |
| AVA Brothers Construct Ltd | Construction | 2021 |
| Avaaron Ltd | Real estate | 2020 |
| Avad Consultants Ltd | Professional & scientific | 2023 |
| Avady Limited | Transport & logistics | 2015 |
| Aveley Allotment Association | Agriculture & fishing | 2025 |
| Aveley Football Club Limited | Arts & recreation | 2014 |
| Avenue Lodge RTM Company Limited | Households | 2011 |