| Animal Search UK Limited | Administrative & support | 2017 |
| Anjum International Ltd | Information & communication | 2023 |
| Anlin Support Services Limited | Real estate | 2014 |
| Anmaleve Calibration Limited | Professional & scientific | 2013 |
| Annas Consultancy Limited | Health & social care | 2019 |
| Annton Properties Limited | Hospitality | 2010 |
| Anoch Properties Limited | Real estate | 2025 |
| Another Place (Mortgage Brokers) Ltd | Financial services | 2019 |
| ANP Marine & Industrial Ltd | Administrative & support | 2024 |
| Ansimusai Ltd | Information & communication | 2026 |
| Antechamber Music Limited | Information & communication | 2021 |
| Antiques Atlas Limited | Information & communication | 1999 |
| Anuka Jewellery Limited | Manufacturing | 2023 |
| Anvil Design Ltd | Professional & scientific | 2025 |
| ANY Car Group Limited | Administrative & support | 2012 |
| Anyela Limited | Wholesale & retail | 2023 |
| Anything BUT Ordinary Ltd | Professional & scientific | 2017 |
| Aoke Europe UK Ltd | Wholesale & retail | 2025 |
| Apache Home Limited | Construction | 2022 |
| Apcorp Ltd | Administrative & support | 2020 |
| Apeiron Football Ltd | Arts & recreation | 2025 |
| Aperidata Ltd | Administrative & support | 2017 |
| Apex Gym RYP Ltd | Arts & recreation | 2026 |
| Apex Health Ltd | Health & social care | 2014 |
| Apex Homes Limited | Construction | 2014 |
| Apex Leadership Ltd | Professional & scientific | 2009 |
| Apex Marketing Services Limited | Professional & scientific | 2016 |
| Apex Running Limited | Arts & recreation | 2021 |
| Apexxpay Ltd | Professional & scientific | 2024 |
| Aphelion Agency Ltd | Professional & scientific | 2021 |
| Apollo Radiology Limited | Health & social care | 2019 |
| Apostle Movement Ltd | Professional & scientific | 2025 |
| Apox Limited | Financial services | 2018 |
| Appell (1957) Limited | Real estate | 2017 |
| Apple Sound Ltd | Administrative & support | 1995 |
| Appleton Logistics Limited | Construction | 2018 |
| Appletree Acquisations Limited | Real estate | 2018 |
| Applied Security Ltd | Administrative & support | 2025 |
| Aptcrete Limited | Real estate | 1984 |
| Aptitude Health & Fitness Ltd | Arts & recreation | 2020 |
| Aqord Limited | Manufacturing | 2006 |
| Aqua Associates Limited | Financial services | 2019 |
| Aqua Hygiene Products Limited | Manufacturing | 1997 |
| Aquaflux Limited | Manufacturing | 2007 |
| Aquair International Limited | Hospitality | 1992 |
| Aquapress Dispense Limited | Professional & scientific | 2024 |
| Aquercia Ltd | Professional & scientific | 2015 |
| Aquila DOR Limited | Financial services | 2021 |
| AR Equine Veterinary Dentistry Ltd | Professional & scientific | 2019 |
| AR Future Limited | Real estate | 2017 |
| AR Wing Kitchen Installations Limited | Construction | 2018 |
| AR Y LAN Ltd | Real estate | 2016 |
| Arab International Investment & Business Limited | Real estate | 2023 |
| Aran Ridge Limited | Real estate | 2019 |
| Arbour ROC Estates Ltd | Real estate | 2024 |
| ARC Dental Limited | Health & social care | 2014 |
| ARC Global Enterprises Limited | Administrative & support | 2017 |
| Arcaxx Group Ltd | Construction | 2025 |
| Arcc HR Ltd | Professional & scientific | 2015 |
| Arcfrancis Ltd | Administrative & support | 2025 |
| Archangel Management Solutions Limited | Professional & scientific | 2025 |
| Architech Laboratory Ltd | Manufacturing | 2024 |
| Architecture Works Ltd | Professional & scientific | 2014 |
| Architeq Ltd | Information & communication | 2022 |
| Archway Groundworks Ltd | Construction | 2016 |
| Archway Holdings Ltd | Financial services | 2016 |
| Archway Restaurant Limited | Hospitality | 2002 |
| ARD Times Ltd | Hospitality | 2025 |
| Arda Fish Bar Ltd | Hospitality | 2026 |
| Ardagh Metal Packaging Trading UK Limited | Administrative & support | 2011 |
| Ardenbridge & Partners Ltd | Financial services | 2026 |
| Ardern Marine and Offshore Services Limited | Transport & logistics | 2018 |
| Ardet Construction Ltd | Construction | 2019 |
| Ardet Jones Limited | Construction | 2020 |
| Ardhi Properties Ltd | Real estate | 2022 |
| Arena Renewables Ltd | Energy | 2021 |
| Ares Cleaning Solutions Limited | Other services | 2017 |
| Ares Sentinel Limited | Information & communication | 2024 |
| Arfon Dwyfor Training (WBL) Limited | Education | 2022 |
| Arfon Dwyfor Training Limited | Financial services | 1983 |
| Argoed Business Services Limited | Professional & scientific | 2004 |
| Argyle Farmers Limited | Agriculture & fishing | 2015 |
| Arham Associates Limited | Health & social care | 2018 |
| Arhm Ltd | Health & social care | 2016 |
| Aria Healthcare Limited | Wholesale & retail | 2009 |
| Arion Project Management Limited | Professional & scientific | 2013 |
| Arise Distribution Limited | Wholesale & retail | 2023 |
| ARK Search Limited | Administrative & support | 2021 |
| Arlo Property Ltd | Real estate | 2020 |
| Armstrong Properties (Westpoint) Limited | Real estate | 2014 |
| ARMSTRONGB2B Limited | Extraterritorial | 2023 |
| Arnada Property Ltd | Households | 2022 |
| Aroma Cafe Bar Limited | Wholesale & retail | 2004 |
| Aronnax Ultrasound Limited | Professional & scientific | 2022 |
| ARP Creations Ltd | Manufacturing | 2024 |
| Arpachem Limited | Wholesale & retail | 2017 |
| Arpadis UK Limited | Wholesale & retail | 2004 |
| Arpette Ltd | Real estate | 2021 |
| Array Technology and Distribution Limited | Information & communication | 2002 |
| Arro Associates Unlimited | Financial services | 2024 |