| Alexander Heating Installations Ltd | Construction | 2025 |
| Alexander Projects Limited | Construction | 2016 |
| Alexandra Noble Design Ltd | Other services | 2020 |
| Alexeiconstruct Limited | Construction | 2019 |
| Alextanks Ltd | Construction | 2026 |
| Alexym Transport Solutions Ltd | Transport & logistics | 2025 |
| Alfresco Air Limited | Construction | 2012 |
| Alger Investment Company | Financial services | 2022 |
| Aliaman Properties Limited | Real estate | 2024 |
| Aliboma Ltd | Other services | 2023 |
| Alicatjam | Financial services | 2018 |
| Alice Lascelles Limited | Professional & scientific | 2026 |
| Alice Thomas Family Law Limited | Professional & scientific | 2020 |
| Alices Swim School Limited | Education | 2026 |
| Alien Heist Ltd | Wholesale & retail | 2025 |
| Aling Maring Ltd | Wholesale & retail | 2024 |
| Alisha Faith Interiors Ltd | Wholesale & retail | 2019 |
| Alkelv Limited | Real estate | 2012 |
| ALL About Alpacas Ltd | Agriculture & fishing | 2024 |
| ALL About Community CIC | Education | 2024 |
| ALL Aspects Roofing Contractors Limited | Construction | 2025 |
| ALL Broadcast Wireless Limited | Information & communication | 2016 |
| ALL DRY Damp Proofing Limited | Construction | 2011 |
| ALL DRY Properties Ltd | Real estate | 2020 |
| ALL in One Group Limited | Construction | 2004 |
| ALL in One Group of Companies Limited | Construction | 2023 |
| ALL of US Investments Ltd | Real estate | 2022 |
| ALL Smart Training Ltd | Education | 2017 |
| ALL Star Property and Development Ltd | Real estate | 2025 |
| ALL Stripes Ltd | Information & communication | 2022 |
| ALL Things Procurement Limited | Professional & scientific | 2019 |
| Allatt Lettings Limited | Real estate | 2001 |
| Allatt’S Haulage Limited | Transport & logistics | 2021 |
| Allen Building & Joinery Services Limited | Construction | 2022 |
| Allen Design Limited | Professional & scientific | 2000 |
| Allen Gardens Management Company Limited | Households | 2002 |
| Allendale Fisheries Limited | Hospitality | 2025 |
| Allendale Store Ltd | Wholesale & retail | 2016 |
| Alliance Business Computers Limited | Information & communication | 1983 |
| Alliance Computer Holdings Limited | Information & communication | 1996 |
| Alliance Document Solutions Limited | Information & communication | 1996 |
| Alliance Roofing Yorkshire Ltd | Construction | 2021 |
| Allied Associates Care Services Ltd | Health & social care | 2024 |
| Allied Excel Limited | Real estate | 2006 |
| Allied Textile Companies Limited | Professional & scientific | 1904 |
| Allied Textiles Limited | Administrative & support | 2000 |
| Alligator Signs Ltd | Manufacturing | 2015 |
| Allisgoodyorkshire Ltd | Wholesale & retail | 2021 |
| Allister Lines Ltd | Transport & logistics | 2026 |
| Allora Creative Ltd | Wholesale & retail | 2023 |
| Allott's Gates Limited | Manufacturing | 2023 |
| Alltek Plastering & Rendering Ltd | Construction | 2026 |
| Allto Limited | Construction | 2018 |
| ALM Property Developments Limited | Construction | 2013 |
| Alma Spine Ltd | Health & social care | 2026 |
| Almaznaz Ltd | Other services | 2019 |
| ALN Property Services Ltd | Hospitality | 2026 |
| Alnahhal.Ortho Limited | Health & social care | 2021 |
| ALO Ball Properties Ltd | Real estate | 2022 |
| ALO Electrical Ltd | Construction | 2025 |
| ALP Productions Limited | Arts & recreation | 2006 |
| Alpa Reale International Limited | Wholesale & retail | 2005 |
| Alpha Joinery & Carpentry Ltd | Construction | 2023 |
| Alpha Joinery & Timberframe Specialists Limited | Construction | 2020 |
| Alpha Leads Operations Limited | Transport & logistics | 2024 |
| Alpha Roof Coatings Limited | Construction | 2024 |
| Alpha-Lead Ltd | Transport & logistics | 2020 |
| Alpharisk Ltd | Financial services | 2019 |
| Alpine Scaffolding Access Ltd | Construction | 2026 |
| Alpro Group Ltd | Administrative & support | 2021 |
| Alreyt Ltd | Wholesale & retail | 2025 |
| Alta Engineering Ltd | Manufacturing | 2002 |
| Altair Roofing Ltd | Construction | 2025 |
| Alteos Partners Limited | Administrative & support | 2020 |
| Altera Design & Build Ltd | Construction | 2025 |
| Altura Build Group Ltd | Construction | 2025 |
| Alturium Ltd | Real estate | 2024 |
| Alusec Architectural Aluminium Limited | Manufacturing | 2011 |
| Alusec UK Limited | Manufacturing | 1993 |
| Always Networks Ltd | Information & communication | 2014 |
| Alymica Trans Ltd | Transport & logistics | 2024 |
| Alyn & Alyna Ltd | Wholesale & retail | 2023 |
| Alyssa Trans Ltd | Transport & logistics | 2022 |
| AM Autos (Barnsley) Ltd | Wholesale & retail | 2020 |
| AM Building & Developments Ltd | Manufacturing | 2019 |
| AM Houses Ltd | Real estate | 2019 |
| AM Scaffolding Ltd | Construction | 2025 |
| AMA Wakefield Limited | Hospitality | 2019 |
| Amary Yoga Retreats Ltd | Arts & recreation | 2025 |
| Amazelab Ltd | Education | 2020 |
| Amazing Helping Hands Limited | Other services | 2021 |
| Amazon Rainwater Systems Limited | Construction | 2004 |
| AMB Electrical Contractors Ltd | Construction | 2023 |
| AMB Engineering (UK) Limited | Manufacturing | 2006 |
| Amberstar Landscapes Ltd | Professional & scientific | 2025 |
| Amber’S Home Luxury Designs Limited | Professional & scientific | 2024 |
| Ambient Home & Garden Limited | Wholesale & retail | 2023 |
| Ambro Property Management Ltd | Real estate | 2021 |
| Amco Corporation Limited | Construction | 2008 |
| Amco of Barnsley Limited | Wholesale & retail | 2009 |