| Artium (Russell ST) Developments Limited | Real estate | 2024 |
| Artium (S1) Developments Limited | Real estate | 2023 |
| Artium (York) Developments Limited | Real estate | 2024 |
| Artium Asset Management Limited | Real estate | 2022 |
| Artium Construction Limited | Construction | 2021 |
| Artium Developments Limited | Construction | 2021 |
| Artium Group Limited | Financial services | 2021 |
| Artium Helios (York) Ltd | Real estate | 2026 |
| Artium Homes Limited | Administrative & support | 2023 |
| Artium Investments Limited | Real estate | 2022 |
| Artium Property Management Limited | Real estate | 2023 |
| Artium Student Living (Bath) Ltd | Real estate | 2026 |
| Artos Innovation Ltd | Professional & scientific | 2013 |
| Arts & Flowers Limited | Wholesale & retail | 2000 |
| Artsmix Leeds Limited | Wholesale & retail | 2011 |
| Artswid Ltd | Professional & scientific | 2024 |
| Artur Rodak Ltd | Manufacturing | 2023 |
| Arturix Educ Limited | Information & communication | 2025 |
| Arturo & Rolando's Ltd | Hospitality | 2020 |
| Artwork P.A. Ltd | Professional & scientific | 2025 |
| Artworks Landscapes & Groundworks Limited | Administrative & support | 2016 |
| Arundel Williams & Surplice Limited | Real estate | 1992 |
| Arus Engineering Limited | Professional & scientific | 2016 |
| Aruws Estates Limited | Real estate | 2023 |
| ARV06 Ltd | Real estate | 2024 |
| Arvans Logistics Ltd | Transport & logistics | 2019 |
| Arvast Limited | Construction | 2025 |
| Arvco Limited | Administrative & support | 2010 |
| Arvee Media Ltd | Professional & scientific | 2025 |
| Arvin Food Market Ltd | Wholesale & retail | 2019 |
| Arvinder Hulait Limited | Real estate | 2025 |
| Arwilcox Ltd | Administrative & support | 2014 |
| ARX Magna Limited | Other services | 2026 |
| ARY Autos Ltd | Wholesale & retail | 2026 |
| Aryaan D & B Ltd | Administrative & support | 2022 |
| Aryan Deliveries Ltd | Transport & logistics | 2025 |
| Aryan Group Ltd | Wholesale & retail | 2025 |
| Aryan Properties (Leeds) Ltd | Real estate | 2022 |
| Aryana Cakery Leeds Ltd | Manufacturing | 2024 |
| Aryana Cakery Ltd | Manufacturing | 2021 |
| Aryn Developments Limited | Construction | 2019 |
| Aryza UK Services Limited | Information & communication | 2017 |
| ARZ Electrical Services Ltd | Manufacturing | 2021 |
| AS Build Group Ltd | Construction | 2026 |
| AS Care Group Limited | Financial services | 2020 |
| AS Carveth Ltd | Administrative & support | 2013 |
| AS FDC Limited | Information & communication | 2024 |
| AS Fruit VEG Ltd | Wholesale & retail | 2025 |
| AS Group International Limited | Professional & scientific | 2021 |
| AS Hear Care Solutions Ltd | Health & social care | 2022 |
| AS Incorporation Limited | Real estate | 2025 |
| AS Joinery Ltd | Construction | 2021 |
| AS Living Spaces Ltd | Real estate | 2026 |
| AS Lounge Ltd | Other services | 2025 |
| AS Read Services Ltd | Other services | 2023 |
| AS Roofing Maintenance Ltd | Construction | 2022 |
| AS S Realisations Limited | Mining & quarrying | 2009 |
| As&W Ltd | Real estate | 2024 |
| As-P Northern Ltd | Manufacturing | 2004 |
| ASA Beauty & Fashion Ltd | Wholesale & retail | 2026 |
| ASA Marketing Ltd | Professional & scientific | 2025 |
| Asak Properties Leeds Ltd | Real estate | 2025 |
| Asam Bashir Ltd | Health & social care | 2010 |
| Asam Holdings Limited | Households | 2024 |
| Asap Property Solutions Ltd | Construction | 2025 |
| Asap Retail Ltd | Wholesale & retail | 2023 |
| Asas Analysis Ltd | Information & communication | 2017 |
| Asatec Ltd | Professional & scientific | 2015 |
| ASB Consultancy Limited | Information & communication | 2024 |
| ASB Delivery Services Limited | Transport & logistics | 2015 |
| ASB Investment Holdings Limited | Financial services | 2024 |
| ASB Moss Ltd | Professional & scientific | 2021 |
| ASC (Leeds) Limited | Construction | 2021 |
| ASC Coaching & Counselling Ltd | Health & social care | 2024 |
| ASC Decorators Limited | Construction | 2022 |
| ASC Engineering Limited | Wholesale & retail | 2004 |
| ASC Mobiles Limited | Wholesale & retail | 2022 |
| Ascend Care Group Ltd | Public administration | 2025 |
| Ascend Hospitality Partners Limited | Professional & scientific | 2025 |
| Ascend Media & Marketing Limited | Other services | 2023 |
| Ascenda Group Ltd | Construction | 2025 |
| Ascension Digital Fine Art Ltd | Arts & recreation | 2023 |
| Ascensor Limited | Information & communication | 2007 |
| Ascensus Consulting Ltd | Information & communication | 2025 |
| Ascent Engineering Ltd | Construction | 2007 |
| Ascent Medical Limited | Health & social care | 2021 |
| Ascent Roofing Limited | Construction | 2012 |
| Ascentx Ltd | Real estate | 2025 |
| Ascnd Holding Ltd | Wholesale & retail | 2026 |
| Ascnt Ltd | Arts & recreation | 2026 |
| Ascolta Limited | Education | 2016 |
| Ascot & Morgan Estate Management Limited | Households | 2025 |
| Ascott IT Solutions Ltd | Information & communication | 2018 |
| Ascott Motors Limited | Wholesale & retail | 2003 |
| ASD (North East) Limited | Professional & scientific | 1905 |
| ASD Court Steel Limited | Professional & scientific | 1967 |
| ASD Limited | Wholesale & retail | 1978 |
| ASD RBS Trustee Limited | Financial services | 2021 |
| ASD Westok Limited | Manufacturing | 2002 |
| Asda Delivery Limited | Construction | 1999 |