| Archytas Strategic Planning Limited | Financial services | 2012 |
| Arckitecoaches Ltd | Professional & scientific | 2025 |
| Arcleap UK Ltd | Information & communication | 2025 |
| Arcm UK Ltd | Hospitality | 2024 |
| Arco Construction Ltd | Professional & scientific | 2017 |
| Arcofm Ltd | Wholesale & retail | 2019 |
| Arcono Jabara Ltd | Real estate | 2021 |
| Arcoppe Limited | Agriculture & fishing | 2023 |
| Arcot Management Company Limited | Other services | 2004 |
| Arcsmith Electrical Ltd | Construction | 2022 |
| Arctic Climate Engineering Ltd | Administrative & support | 2008 |
| Arctic Club Ltd. | Administrative & support | 2018 |
| Arctic Distributors Ltd | Wholesale & retail | 2025 |
| Arctic FOX Technology Ltd | Manufacturing | 2021 |
| Arctic Glaze (Commercial) Limited | Construction | 2019 |
| Arctic Motorsport Ltd | Wholesale & retail | 2022 |
| Arcticfox Skis Ltd | Wholesale & retail | 2025 |
| ARD Al-Khair Al-Mutakamilah Liltanmiyah and Investment Ltd | Wholesale & retail | 2024 |
| ARD Digital Ltd | Information & communication | 2026 |
| ARD Northwest Limited | Health & social care | 2016 |
| ARD PTY Ltd | Real estate | 2019 |
| Ard&Sa Ltd | Wholesale & retail | 2025 |
| ARDA1 Ltd | Wholesale & retail | 2025 |
| Ardani Consultancy Limited | Health & social care | 2023 |
| Ardent Bespoke Services Limited | Financial services | 2017 |
| Ardent Dental Care Ltd | Health & social care | 2018 |
| Ardic Cardiff Ltd | Hospitality | 2025 |
| Ardour Academy Ltd | Health & social care | 2018 |
| Ardra and Athira LLP | | 2018 |
| Ardra and Athira Restaurants Cardiff Ltd | Hospitality | 2022 |
| Ardventure Ltd | Wholesale & retail | 2026 |
| Ardwen Ltd | Information & communication | 2025 |
| ARE YOU Owed Money Limited | Administrative & support | 2014 |
| Areaproof Limited | Real estate | 1999 |
| Aredo Solutions Ltd | Other services | 2019 |
| Areej Trading Ltd | Wholesale & retail | 2006 |
| Arena Direct Ltd | Construction | 2021 |
| Arena Projects Sport and Entertainment Management Ltd | Administrative & support | 2021 |
| Arena Vehicles Ltd | Real estate | 2018 |
| Arenal Estates and Developments Limited | Real estate | 1971 |
| Arencrete Limited | | 1976 |
| Ares Food Limited | Hospitality | 2018 |
| Ares Training Ltd | Education | 2016 |
| Arete Construction Services Ltd | Construction | 2025 |
| Arete Estates Limited | Other services | 2015 |
| Arete Executive Search Ltd | Administrative & support | 2019 |
| Arete Health Marketing Ltd | Professional & scientific | 2024 |
| Arewa Wales Network CIC | Education | 2025 |
| Arezz Ltd | Manufacturing | 2025 |
| ARF Internatinal Ltd | Wholesale & retail | 2026 |
| Arfath Enterprises Ltd | Wholesale & retail | 2024 |
| ARG Solutions International | Administrative & support | 2022 |
| Argent Associates Limited | Professional & scientific | 2011 |
| Argent Avenue Media Limited | Professional & scientific | 2025 |
| Argent Payroll Limited | Professional & scientific | 2014 |
| Argentera Trading PC | | 2019 |
| Argento Wealth Limited | Administrative & support | 2017 |
| Argentum Homes Ltd | Real estate | 2021 |
| Argiis Recruits Ltd | Administrative & support | 2021 |
| Argonaut Systems Ltd | Information & communication | 2007 |
| Argonaut Technologies Ltd | Information & communication | 2017 |
| Argonaute RNA Limited | Professional & scientific | 2015 |
| Argoo UK Ltd | Wholesale & retail | 2025 |
| Argosy Securities Limited | Professional & scientific | 1972 |
| Argus Developments Limited | Wholesale & retail | 2025 |
| Argyle Autos Ltd | Wholesale & retail | 2003 |
| Argyle Investments (Ilford) Limited | Real estate | 2020 |
| ARI Property Limited | Real estate | 2023 |
| Aria Asset Management Ltd | Real estate | 2018 |
| Aria Collection Limited | Real estate | 2026 |
| Aria Hospitality Limited | Hospitality | 2025 |
| Aria Wholesale Vape Ltd | Wholesale & retail | 2022 |
| Ariam Travel Ltd | Transport & logistics | 2011 |
| Ariamson Group Limited | Manufacturing | 2018 |
| Arian Accountants Limited | Professional & scientific | 2008 |
| Arian TV & Film Ltd | Professional & scientific | 2013 |
| Ariana Mobile & Accessories Limited | Wholesale & retail | 2020 |
| Arianer Ltd | Professional & scientific | 2018 |
| Ariavista Ltd | Wholesale & retail | 2025 |
| Aridda Solutions Ltd | Information & communication | 2024 |
| Aries Bridal Services Ltd | Other services | 2025 |
| Aries Hair Extension Ltd | Other services | 2025 |
| Arif Halal Foods Ltd | Wholesale & retail | 2014 |
| Arifk Rentals Ltd | Real estate | 2025 |
| Ario Barzan Ltd | Hospitality | 2018 |
| Arioste Capital Limited | Financial services | 2023 |
| Aris Partners Ltd | Professional & scientific | 2026 |
| Arise & Live Limited | Health & social care | 2013 |
| Aristama Ltd | Wholesale & retail | 2025 |
| Ariston Global (UK) Limited | Professional & scientific | 2018 |
| Ariyan Trading Ltd | Manufacturing | 2025 |
| Arizona Allstars Limited | Education | 2022 |
| ARJ QA Limited | Financial services | 2013 |
| ARJ QCA Limited | Financial services | 2022 |
| ARK Architectural Services Limited | Professional & scientific | 2015 |
| ARK Capital Partners LLP | | 2023 |
| ARK Creat Ltd | Professional & scientific | 2020 |
| ARK Establishment Ltd | Other services | 2019 |
| ARK Group Private Limited | Information & communication | 2018 |
| ARK Holdings Limited | Real estate | 2020 |