| Arbor CAD Limited | Professional & scientific | 2024 |
| Arbor Estates (Walsall) Limited | Real estate | 1978 |
| Arbor Fire and Security Limited | Administrative & support | 2012 |
| Arbor Systems Ltd | Administrative & support | 2025 |
| Arboretum House Limited | Health & social care | 2022 |
| ARC Strategy Ltd | Professional & scientific | 2026 |
| Arcade Super Market Ltd | Wholesale & retail | 2025 |
| Arcadia Land Developments Limited | Construction | 2015 |
| Arcadia Talent Group Limited | Administrative & support | 2025 |
| Archiesoul Ltd | Wholesale & retail | 2018 |
| Architectural Envelope Solutions Ltd | Manufacturing | 2024 |
| Architectural Maintenance Services Limited | Construction | 2015 |
| Architettura Design Ltd | Professional & scientific | 2019 |
| Archway Horizon Limited | Manufacturing | 2021 |
| Arco Properties Limited | Real estate | 2000 |
| Arcs N Sparks Corporate Clothing Limited | Wholesale & retail | 2007 |
| Arctic Building Communities CIC | Water & waste | 2024 |
| Arden Financial Services Ltd | Financial services | 2024 |
| Ardian Parcel Ltd | Transport & logistics | 2024 |
| Ardor OLK Ltd | Wholesale & retail | 2021 |
| Areej London Limited | Manufacturing | 2023 |
| Areha Ltd | Construction | 2023 |
| Areley Healthcare Limited | Extraterritorial | 2025 |
| ARG Resources Limited | Professional & scientific | 2014 |
| Argarloom Ltd | Transport & logistics | 2024 |
| Ari-Kav Limited | Hospitality | 2020 |
| Aria Property Management Ltd | Households | 2025 |
| Arian Investment Group Limited | Financial services | 2021 |
| Ariana Kitchens & Bedrooms Limited | Other services | 2025 |
| Arie Solutions Ltd | Agriculture & fishing | 2023 |
| Arien Design & Build Ltd | Professional & scientific | 2021 |
| Arien Group Ltd | Professional & scientific | 2021 |
| Arien Properties Ltd | Real estate | 2021 |
| Arise Helping Hands CIC | Administrative & support | 2022 |
| Arise Housing Ltd | Health & social care | 2020 |
| Arissa Care Limited | Real estate | 2024 |
| ARJ Locum Ltd | Professional & scientific | 2019 |
| ARK Care Staff Limited | Administrative & support | 2026 |
| ARK Environmental Services Limited | Water & waste | 2009 |
| ARK Management & IT Services Limited | Information & communication | 2010 |
| ARK Sales & Lettings Ltd | Households | 2019 |
| Arkclothing Limited | Wholesale & retail | 2023 |
| Arli Group Ltd | Construction | 2024 |
| ARM Mansfield Ltd | Other services | 2018 |
| Arma Healthcare Ltd | Wholesale & retail | 2026 |
| Armaan Transport Limited | Transport & logistics | 2017 |
| Armac Martin Limited | Manufacturing | 2025 |
| Armani Transport Ltd | Transport & logistics | 2023 |
| Armastus Ltd | Information & communication | 2024 |
| Armi Forever Limited | Wholesale & retail | 2024 |
| Armour Track Limited | Wholesale & retail | 2024 |
| Arnold Maintenance Limited | Administrative & support | 2024 |
| Aroa Residences Ltd | Hospitality | 2025 |
| Aroi-Sj Ltd | Hospitality | 2022 |
| Aromax Logistics Ltd | Transport & logistics | 2025 |
| Aromepur Limited | Health & social care | 2008 |
| Arps (Staffs) Limited | Construction | 2024 |
| Arrali Ltd | Professional & scientific | 2024 |
| Arrey Consultants Ltd | Information & communication | 2015 |
| Arrive in Style Limited | Transport & logistics | 1998 |
| Arrow Installations Ltd | Construction | 2011 |
| Arrow Logistics U.K. Ltd | Transport & logistics | 2023 |
| Arrowsmith-Cox Accountancy Services Ltd | Professional & scientific | 2025 |
| Arsish Limited | Wholesale & retail | 2023 |
| Artemis Birth Attendant Academy Ltd | Health & social care | 2022 |
| Artha Technology Limited | Information & communication | 2021 |
| Arthrous Limited | Professional & scientific | 2024 |
| Artic Scenery Ltd | Arts & recreation | 2019 |
| Artisan Shropshire Ltd | Construction | 2017 |
| Artisanary Ltd | Extraterritorial | 2023 |
| Artistic Gardens Ltd | Administrative & support | 2017 |
| Artr Investments Limited | Real estate | 2023 |
| ARU Heating Ltd | Construction | 2022 |
| Arvadarenettico Ltd | Wholesale & retail | 2021 |
| Arvis Construction Ltd | Construction | 2026 |
| Arvp Services Ltd | Wholesale & retail | 2025 |
| ARY Alaskan Ice Limited | Hospitality | 2026 |
| ARY Trading Ltd | Other services | 2020 |
| Arya Real Estate Ltd | Real estate | 2022 |
| Aryka Investments Limited | Real estate | 2021 |
| Aryoub Bazaar Limited | Wholesale & retail | 2025 |
| Aryoub Supermarket Ltd | Wholesale & retail | 2023 |
| AS Bassi Ltd | Administrative & support | 2016 |
| AS Erra Ltd | Wholesale & retail | 2025 |
| AS Facilities Management Ltd | Administrative & support | 2025 |
| AS Financial Solutions Limited | Professional & scientific | 2017 |
| AS Powar Constructions Ltd | Construction | 2018 |
| AS Properties (Midlands) Limited | Real estate | 2021 |
| AS Retail Direct Limited | Wholesale & retail | 2024 |
| Asalam Ltd | Transport & logistics | 2023 |
| Asarf Limited | Water & waste | 2014 |
| ASB Builders Ltd | Construction | 2024 |
| ASB Pharma Ltd | Professional & scientific | 2023 |
| ASB Real Estate Ltd | Real estate | 2021 |
| Asbury Mechanical Estimating Services Limited | Professional & scientific | 2014 |
| ASC Ebridge Limited | Information & communication | 2023 |
| Ascetic Focus Ltd | Information & communication | 2025 |
| Asclepius Medicare Ltd | Health & social care | 2021 |
| Ascot MOT Centre Ltd | Wholesale & retail | 2022 |
| ASD Homes Limited | Real estate | 2020 |