| Archifos Ltd | Professional & scientific | 2025 |
| Archon Outbound Ltd | Professional & scientific | 2024 |
| Arcitile Limited | Construction | 2017 |
| Arcology System Limited | Manufacturing | 2019 |
| Arctic Foods Limited | Wholesale & retail | 2002 |
| Arctic Island Ltd | Wholesale & retail | 2023 |
| ARD Store Ltd | Wholesale & retail | 2025 |
| Arden Apartments Limited | Real estate | 2017 |
| Arden Guest House Limited | Hospitality | 2023 |
| Arden Park Garage Services Limited | Wholesale & retail | 2005 |
| Arden Park Rental Properties Limited | Real estate | 2018 |
| Ardent Business Consulting Limited | Information & communication | 2007 |
| Ardent Care Group Ltd. | Administrative & support | 2019 |
| Ardent Edge Limited | Wholesale & retail | 2025 |
| Ardent Gray Ltd | Administrative & support | 2023 |
| Ardent Law Services Ltd | Professional & scientific | 2023 |
| Ardent Sports Ltd | Professional & scientific | 2017 |
| Ardentis Consulting Ltd | Professional & scientific | 2026 |
| Ardetrans-Recruitment Limited | Administrative & support | 2025 |
| Ardhya Properties Limited | Real estate | 2020 |
| Ardmore Education Limited | Education | 2016 |
| Ardmore Educational Travel Limited | Education | 1984 |
| Ardmore Language Schools Limited | Education | 1982 |
| Ardour Energy Consultants Limited | Professional & scientific | 2024 |
| Ardrox Limited | Extraterritorial | 1948 |
| ARE WE Limited | Other services | 2020 |
| Area Building Contractors Limited | Construction | 2024 |
| Areen Car Valeting Ltd | Administrative & support | 2023 |
| Areille Ltd | Health & social care | 2019 |
| Arena Views Ltd | Construction | 2025 |
| Arequest Limited | Professional & scientific | 2024 |
| Arevana Limited | Hospitality | 2016 |
| Arez Medics Limited | Health & social care | 2014 |
| Argardens Ltd | Administrative & support | 2019 |
| Argenesis Limited | Administrative & support | 2022 |
| Argo Procurement Services Limited | Professional & scientific | 2009 |
| Argon Refrigeration Services Ltd | Manufacturing | 2015 |
| Argosy Engineering Services Limited | Manufacturing | 2016 |
| Argus IT Ltd | Information & communication | 2002 |
| Argyle Care Group Limited | Health & social care | 2002 |
| Argyle Electrical MK Limited | Administrative & support | 2016 |
| ARI Gradi Ltd | Professional & scientific | 2024 |
| ARI Interiors Ltd | Professional & scientific | 2023 |
| ARI Studio Ltd | Wholesale & retail | 2018 |
| Ari-O Commerce Connect Ltd | Wholesale & retail | 2024 |
| Ari-O Consulting Ltd | Professional & scientific | 2022 |
| Aria (MK) Ltd | Health & social care | 2023 |
| Aria BE Ltd | Manufacturing | 2020 |
| Aria Consulting Engineers Limited | Information & communication | 2015 |
| Aria Developments Limited | Wholesale & retail | 2002 |
| Aria Innovation Limited | Professional & scientific | 2008 |
| Aria Wheels UK Ltd | Wholesale & retail | 2025 |
| Ariadna Trans Limited | Transport & logistics | 2021 |
| Ariasterl Limited | Information & communication | 2026 |
| Aries Investments Two Limited | Financial services | 2019 |
| Arika Face & Body N B Aesthetics Limited | Other services | 2025 |
| Arim Consultancy Limited | Manufacturing | 2020 |
| Arin Edge Ltd | Administrative & support | 2024 |
| Arisa Holdings & Investment Ltd | Real estate | 2025 |
| Arisaltas Limited | Professional & scientific | 2024 |
| Arisan Ltd | Health & social care | 2021 |
| Arise Solutions Limited | Information & communication | 2011 |
| Arisoo Consult Limited | Health & social care | 2015 |
| Aristo Photography Limited | Professional & scientific | 2012 |
| Aristocars Limited | Wholesale & retail | 2020 |
| Arivuu AI Ltd | Information & communication | 2025 |
| Arizsports Ltd | Wholesale & retail | 2018 |
| ARJ Print UK Ltd | Manufacturing | 2026 |
| ARK Consulting & Tax Ltd | Professional & scientific | 2017 |
| ARK DIY Ltd | Construction | 2024 |
| ARK Kitchen Services Ltd | Manufacturing | 2019 |
| ARK Medical Consultancy Ltd | Health & social care | 2023 |
| ARK Wildlife Limited | Wholesale & retail | 2007 |
| Arkadia Clinical Solutions Limited | Health & social care | 2025 |
| Arkin Consulting Ltd | Professional & scientific | 2026 |
| Arkle Automotive Project Engineering Ltd | Administrative & support | 2012 |
| Arlan Property Holdings Ltd | Real estate | 2018 |
| Arlesey Road (Stotfold) Residents Management Company Limited | Households | 2019 |
| Arlo Pro Ltd | Transport & logistics | 2022 |
| ARM 92 Ltd | Wholesale & retail | 2024 |
| ARM Concepts Limited | Construction | 2018 |
| ARM Export & Import Ltd | Wholesale & retail | 2026 |
| Armadillo Newmedia Limited | Information & communication | 1999 |
| Armagado Lifestyle Ltd | Manufacturing | 2020 |
| Armani Trading Limited | Wholesale & retail | 2017 |
| Armbrella Ltd | Arts & recreation | 2025 |
| Armd-Uk Ltd | Professional & scientific | 2025 |
| Armiar Investments Limited | Real estate | 2018 |
| Armieri Holdings LLP | | 2023 |
| Armitage Consultants Limited | Professional & scientific | 2010 |
| Armitage Homes Limited | Construction | 1996 |
| Armour Systems Limited | Manufacturing | 2013 |
| Armoured Construction Ltd | Construction | 2017 |
| Armtech Global Services Limited | Administrative & support | 2022 |
| Armyltelcom Ltd | Wholesale & retail | 2025 |
| Arna Estates Ltd | Real estate | 2024 |
| Arnav Properties Limited | Real estate | 2020 |
| Arnold Healthcare Ltd | Health & social care | 2019 |
| Arnolds Electrical Limited | Wholesale & retail | 2003 |
| Arod Services Ltd | Administrative & support | 2024 |