| Annaya and Watkins Limited | Hospitality | 2025 |
| Annieanne Limited | Manufacturing | 2014 |
| Another New Home Ltd | Real estate | 2019 |
| Ansell Village Stores Limited | Hospitality | 2005 |
| Antalya Delicious Ltd | Hospitality | 2025 |
| Antares Capital Investments Ltd | Financial services | 2021 |
| Antep Grill House Ltd | Hospitality | 2025 |
| Anthony a Davies Holdings Limited | Financial services | 2024 |
| Anthony a Davies Limited | Manufacturing | 1997 |
| Anthony Gibbons Design & Build Ltd | Construction | 2018 |
| Anthony Gibbons Investments Ltd | Financial services | 2021 |
| Anthony Harris Carpentry Ltd | Manufacturing | 2006 |
| Anthony P Williams Limited | Manufacturing | 2018 |
| Anti-Comfort Club Ltd | Wholesale & retail | 2026 |
| Antmet Solutions Limited | Professional & scientific | 2018 |
| ANU & Atul Kalhan Limited | Education | 2016 |
| Anubis Games Limited | Information & communication | 2023 |
| Anvil Consultants Limited | Professional & scientific | 2006 |
| ANY Location Services Ltd | Public administration | 2017 |
| Anyxia Limited | Information & communication | 2015 |
| AOF Rugby Limited | Arts & recreation | 2024 |
| AP Higgs Engineering Ltd | Real estate | 2014 |
| AP Lamp Distributors Limited | Wholesale & retail | 1997 |
| APC Utilities Ltd | Information & communication | 2025 |
| APE Vape Holdings Limited | Financial services | 2026 |
| APE Vape Limited | Manufacturing | 2017 |
| Apeiron Group Limited | Financial services | 2020 |
| Apeiron Property Limited | Construction | 2020 |
| Apeiron Sport Limited | Manufacturing | 2020 |
| Apeiron Wealth Management Limited | Financial services | 2024 |
| Apex Computer Recycling Limited | Information & communication | 2025 |
| Apex Computer Services (Wales) Limited | Information & communication | 1994 |
| Apex EDUC8 Ltd | Administrative & support | 2024 |
| Apex Joinery and Shopfitting (Wales) Ltd | Manufacturing | 2003 |
| Apex Photocopying Limited | | 1989 |
| Apex Site Security Ltd | Administrative & support | 2026 |
| Apex Tattoo Care Ltd | Extraterritorial | 2023 |
| Apex Warehouse Ltd | Wholesale & retail | 2018 |
| Apexchase Competitions Limited | Wholesale & retail | 2026 |
| Apextorque Motors Ltd | Wholesale & retail | 2026 |
| Apnj Consulting Limited | Administrative & support | 2021 |
| Apogee Property and Utility Consultants Limited | Professional & scientific | 2018 |
| Apollo Industrial Doors Limited | Manufacturing | 2008 |
| Apollo Property Projects Limited | Real estate | 2015 |
| Apollo-Xi Ltd | Wholesale & retail | 2024 |
| Apple Accountancy Ltd | Professional & scientific | 2018 |
| Apple Tree Cottage Enterprises Limited | Hospitality | 2015 |
| Appley GAS Services (Isle of Wight) Limited | Manufacturing | 2009 |
| Appley Sands Management Company Limited | Real estate | 2006 |
| Applied Insight Limited | Professional & scientific | 2003 |
| Applied Pipework Ltd | Construction | 2012 |
| Approved Life Ltd | Financial services | 2018 |
| Appsent.Me.Uk Limited | Professional & scientific | 2023 |
| APR Mortgages Ltd | Financial services | 2016 |
| APS Automotive Limited | Wholesale & retail | 2001 |
| Apter Consulting Ltd | Professional & scientific | 2021 |
| Aqsa Travels Ltd | Administrative & support | 2018 |
| Aqualate Castle Holdings Limited | Agriculture & fishing | 2022 |
| Aqualate Pool Services Ltd | Construction | 2021 |
| Aquascan International Limited | Manufacturing | 1982 |
| Aquatic Engineering Limited | Manufacturing | 2008 |
| Aquila Electronics Limited | Manufacturing | 1999 |
| Aquire IT Ltd | Information & communication | 2023 |
| Aquus Limited | Information & communication | 2018 |
| AR & R Research Enterprises Ltd | Professional & scientific | 2026 |
| AR Digital Limited | Manufacturing | 2003 |
| AR IT Support Limited | Information & communication | 2020 |
| Aragon House Management Limited | Hospitality | 1986 |
| Arap Medic Ltd | Health & social care | 2023 |
| Arbel Properties Ltd | Real estate | 2025 |
| Arbour Farms Limited | Agriculture & fishing | 2010 |
| Arcadia After Hours Limited | Hospitality | 2024 |
| Arcadia Cafe & Bistro Limited | Hospitality | 2024 |
| Arcadia Care Homes Limited | Health & social care | 2011 |
| Arcadia Coffee House Limited | Hospitality | 2022 |
| Arcadia Marshall Developments Limited | Real estate | 2022 |
| Arcadia Marshall Holdings Limited | Financial services | 2024 |
| Arcam-B Limited | Financial services | 2025 |
| Archangel Ventures Limited | Professional & scientific | 2011 |
| Archery GB Limited | Arts & recreation | 2006 |
| Archery UK Limited | Arts & recreation | 2003 |
| Architectural Services (Building & Civil Engineering) Limited | Construction | 1997 |
| Architexture Limited | Professional & scientific | 2006 |
| Archkabe Ltd | Financial services | 2025 |
| Archon Developments Ltd | Construction | 2026 |
| Arclay Consulting Limited | Professional & scientific | 2026 |
| Arctic Healthcare Ltd | Health & social care | 2026 |
| Ardos Barber Shop Ltd | Other services | 2025 |
| Area 37 Limited | Hospitality | 2009 |
| Arena (Eyewear) Limited | Wholesale & retail | 1989 |
| Arewa Properties Limited | Real estate | 2020 |
| Arewen Consultancy Limited | Professional & scientific | 2008 |
| Arewen Limited | Extraterritorial | 2003 |
| Arewen Pets Limited | Wholesale & retail | 2005 |
| Argyle Developments (Newport) Limited | Real estate | 1903 |
| Arian Care Ltd. | Health & social care | 2013 |
| Arian Finance Limited | Financial services | 1995 |
| Arise Shine Light CIC | Other services | 2025 |
| Arise Towers Limited | Real estate | 2024 |
| Arista Hairdressing Ltd | Other services | 2021 |