| Almond Boxing Academy C.I.C. | Education | 2018 |
| Alomain Ltd | Transport & logistics | 2020 |
| ALP International Ltd | Wholesale & retail | 2023 |
| Alpaho International Ltd | Information & communication | 2025 |
| Alpha Development Management Solutions Ltd | Construction | 2019 |
| Alpha Dispatch Services Ltd | Transport & logistics | 2025 |
| Alpha Domain Development Ltd | Professional & scientific | 2008 |
| Alpha Integrated Management Systems Ltd | Extraterritorial | 2024 |
| Alpha Life Cleaning Limited | Administrative & support | 2024 |
| Alpha Safety Team Ltd | Professional & scientific | 2019 |
| Alphadata Technology Limited | Professional & scientific | 1997 |
| Alpina Motor Ltd | Wholesale & retail | 2025 |
| Alport Opportunities Ltd | Construction | 2014 |
| Already Ltd | Information & communication | 2024 |
| Alrian Industries Limited | Information & communication | 1986 |
| ALS Retail Ltd | Professional & scientific | 2020 |
| Alsalam Medical Ltd | Health & social care | 2025 |
| Alsat Ltd | Wholesale & retail | 2025 |
| Altavista Holdings Ltd | Real estate | 2025 |
| Alternative Identity Limited | Other services | 2017 |
| Alti Access Limited | Construction | 2024 |
| Altico (Holdings) Ltd | Wholesale & retail | 2021 |
| Altico Garden Products Ltd | Wholesale & retail | 2013 |
| Altitude Rope Access Limited | Construction | 2011 |
| Altitude Tattoo Limited | Arts & recreation | 2019 |
| Altivon Labs Ltd | Extraterritorial | 2026 |
| Alto Construct Ltd | Construction | 2016 |
| Alto Plant Limited | Administrative & support | 2019 |
| Alucor Limited | Manufacturing | 2021 |
| Aluminium First Limited | Manufacturing | 2017 |
| Alverra Holdings Ltd | Extraterritorial | 2026 |
| Alwaliy Limited | Real estate | 2021 |
| ALY IAN Ltd | Transport & logistics | 2019 |
| ALY VIC Ltd | Transport & logistics | 2022 |
| Alycidon Homes Limited | Construction | 2015 |
| Alzbeta Retail Ltd | Wholesale & retail | 2025 |
| AM Fitness and Health Ltd | Arts & recreation | 2026 |
| AM Island Koncept Ltd | Real estate | 2024 |
| AM Rail Services UK Limited | Construction | 2025 |
| AM Rigging Ltd | Construction | 2021 |
| AMA Engineering Consultants Ltd | Professional & scientific | 2015 |
| Amaar One Ltd | Administrative & support | 2025 |
| Amack Consulting Ltd | Professional & scientific | 2015 |
| Amadeus Enterprises Limited | Information & communication | 2017 |
| Amajust Limited | Administrative & support | 2024 |
| Aman Healthcare Ltd | Health & social care | 2015 |
| Amanda Jayne Thompson Ltd | Health & social care | 2023 |
| Amans Vape Outlet Ltd | Wholesale & retail | 2022 |
| Amar Dhami Limited | Wholesale & retail | 2006 |
| Amar Zarif Limited | Professional & scientific | 2017 |
| Amara Care Solutions Ltd | Administrative & support | 2023 |
| Amasya Transport Ltd | Transport & logistics | 2019 |
| Amatransport Logistic Ltd | Transport & logistics | 2025 |
| Amaze Estates Limited | Construction | 2020 |
| Amaze Group Ltd | Financial services | 2026 |
| Amazecard Limited | Information & communication | 2026 |
| Amazing IOT Systems Limited | Information & communication | 2022 |
| Amazone Developments Ltd | Construction | 2014 |
| Amazone Limited | Wholesale & retail | 1982 |
| Ambagarth Holdings Limited | Professional & scientific | 2016 |
| Ambar Subway Limited | Hospitality | 2014 |
| Ambassador Seafoods Limited | Manufacturing | 2009 |
| Amber Care (East Anglia) Ltd | Health & social care | 2003 |
| Amberstone Developments (Northern) Limited | Real estate | 2002 |
| Amberstone Developments Limited | Construction | 2001 |
| Ambilicious LLP | | 2016 |
| Ambispace Limited | Manufacturing | 2016 |
| Ambitious Supported Living Ltd | Health & social care | 2021 |
| Ambo Ltd | Professional & scientific | 2002 |
| AMC Rail Training Ltd | Education | 2024 |
| AMC Yorkshire Ltd | Construction | 2022 |
| Amcb Consultancy Services Limited | Transport & logistics | 2021 |
| Amco of Doncaster Limited | Wholesale & retail | 2009 |
| Amcss Ltd | Health & social care | 2025 |
| AMDEL17 Limited | Transport & logistics | 2017 |
| AME Contracting Ltd | Construction | 2020 |
| Ameg-Group Limited | Professional & scientific | 2021 |
| Amelia Rose Children's Wear Limited | Wholesale & retail | 2020 |
| Amen House Ltd | Real estate | 2025 |
| Amet Group Limited | Administrative & support | 2020 |
| Amethyst Business Consulting Ltd | Professional & scientific | 2025 |
| AMF Roofing Contractors Limited | Construction | 1998 |
| AMG Automotive Services Ltd | Wholesale & retail | 1995 |
| AMG Contracting Limited | Professional & scientific | 2015 |
| AMH Accountancy Services Limited | Professional & scientific | 2002 |
| AMI Golf Limited | Arts & recreation | 2025 |
| Amir Properties (UK) Limited | Real estate | 2007 |
| Amjad Holdings Ltd | Real estate | 2024 |
| AML Juratek Limited | Financial services | 2019 |
| Ammad Hassan Ltd | Wholesale & retail | 2026 |
| Ammini's Kitchen Ltd | Wholesale & retail | 2024 |
| Amnack Limited | Manufacturing | 1996 |
| Amongst Others Ltd | Arts & recreation | 2011 |
| Amore Luxe Collection Ltd | Wholesale & retail | 2025 |
| AMP Contract Office Ltd | Administrative & support | 2025 |
| AMP Contract Solutions Ltd | Administrative & support | 2025 |
| AMP Contract Support Ltd | Construction | 2025 |
| AMP Renewable Energy Ltd | Construction | 2020 |
| AMP5 Contracts Limited | Construction | 2012 |
| Ample Power Electrical Limited | Construction | 2019 |