| Alexia Capital Management Limited | Financial services | 2015 |
| Alfold (Loxwood Road) Management Company Limited | Households | 2022 |
| Alhassomicrophones Ltd. | Professional & scientific | 2024 |
| Aliance Auto Services Ltd | Wholesale & retail | 2023 |
| Alibuildworkssolutions Limited | Construction | 2025 |
| Alice Otieno Ltd | Administrative & support | 2023 |
| Alifr Ltd | Information & communication | 2025 |
| Alifrp Ltd | Real estate | 2025 |
| Alistair Dance Ltd | Professional & scientific | 2025 |
| Alive Comms Group Limited | Financial services | 2018 |
| Alive Communications Limited | Professional & scientific | 1999 |
| Aljac Fuelling Components Limited | Manufacturing | 1988 |
| ALL About the Product Ltd | Information & communication | 2014 |
| ALL Aspects Outdoors Ltd | Administrative & support | 2025 |
| ALL in Stone (South) Ltd | Wholesale & retail | 2020 |
| ALL Things Artisan Ltd | Construction | 2025 |
| ALL True Fitness Ltd | Wholesale & retail | 2022 |
| ALL Your Computers Limited | Information & communication | 2009 |
| All-Pro Pixel Limited | Professional & scientific | 2024 |
| Allen Estates Limited | Extraterritorial | 1997 |
| Allen Pavitt Contracts Limited | Administrative & support | 1987 |
| Allen's PUB and Kitchen Ltd | Hospitality | 2024 |
| Alliance One International Holdings, Ltd. | Financial services | 2018 |
| Alliance One International Services Limited | Administrative & support | 1997 |
| Alliancehr Limited | Professional & scientific | 2005 |
| Alliances Intelligence Ltd | Information & communication | 2025 |
| Alloway Investments Ltd | Administrative & support | 2004 |
| Alonso-Lopez Accountancy Services Ltd | Professional & scientific | 2023 |
| ALP Heating Ltd | Manufacturing | 2021 |
| Alpha Construction Services Limited | Construction | 2026 |
| Alpha Cups Ltd | Hospitality | 2026 |
| Alpha Cuts Limited | Administrative & support | 2017 |
| Alpha Independent Mortgages LLP | | 2004 |
| Alpha MAX Aviation Ltd | Education | 2026 |
| ALPHA3 Holdings Ltd | Real estate | 2023 |
| Alpine Property Intelligence Ltd | Information & communication | 2017 |
| Alrad Instruments Limited | Manufacturing | 1989 |
| Alsco Linen Services Limited | Administrative & support | 2018 |
| Altrasoft Limited | Professional & scientific | 1992 |
| Aluna Surfacing Limited | Construction | 2016 |
| Alvis Limited | Financial services | 1962 |
| Alvis Pension Scheme Trustees Limited | Extraterritorial | 2001 |
| Alvis Vickers Limited | Extraterritorial | 1997 |
| Always Digging Ltd. | Construction | 2016 |
| Always Forward Brand Ltd | Wholesale & retail | 2025 |
| AM Management Consultancy Ltd | Information & communication | 2022 |
| AM Systems Group Ltd | Construction | 2021 |
| AMA Hair Salon Limited | Other services | 2022 |
| Amaan Taxi Ltd | Transport & logistics | 2023 |
| Amalfi Technology Consulting Limited | Information & communication | 2014 |
| Amass Technology Ltd | Professional & scientific | 2022 |
| Amazingcart Limited | Wholesale & retail | 2025 |
| Amazon Filters Limited | Manufacturing | 1977 |
| Amber Homes (Surrey) Limited | Construction | 2005 |
| Amber Spyglass Limited | Information & communication | 2007 |
| Amberley Park (Tetbury) Management Company Limited | Households | 2016 |
| Amberwood Drive Residents Association Limited | Other services | 1979 |
| Ambjack Consultancy Ltd | Information & communication | 2025 |
| Ambrozie Ltd | Transport & logistics | 2017 |
| AMC Strategic Finance Ltd | Professional & scientific | 2026 |
| Amer Sports UK Limited | Manufacturing | 1992 |
| Americandy Inc Limited | Wholesale & retail | 2011 |
| Americatessen Limited | Wholesale & retail | 2017 |
| Amethyst Lettings Holdings Limited | Extraterritorial | 2015 |
| Amethyst Pharma Limited | Professional & scientific | 2011 |
| Amgk Property Limited | Real estate | 2021 |
| Amica Talent Ltd | Administrative & support | 2021 |
| Amicus Estates Limited | Real estate | 2019 |
| Amicus Management Limited | Real estate | 2023 |
| Amira-Maria Ltd | Administrative & support | 2025 |
| Amlat Ltd | Wholesale & retail | 2023 |
| Ammara Internet Limited | Information & communication | 1999 |
| Ammonite Property Developments Limited | Construction | 2023 |
| Ammos Global Limited | Administrative & support | 2026 |
| Amplify Demand Limited | Professional & scientific | 2025 |
| Amrite Health Ltd | Health & social care | 2021 |
| Amtech Electrical Limited | Construction | 2012 |
| AMV Properties Ltd | Real estate | 2023 |
| AN Evolution Project Limited | Arts & recreation | 2013 |
| AN Houses Private Ltd | Real estate | 2026 |
| ANA Consultants U.K. Limited | Information & communication | 2000 |
| Anako Hair & Beauty Salon Ltd | Other services | 2019 |
| Analysis Electrical Limited | Construction | 1991 |
| Ancva Ltd | Education | 2019 |
| AND Co Financial Services Ltd | Real estate | 2004 |
| AND Co Group Ltd | Households | 2010 |
| AND Co Property Services Ltd | Real estate | 2010 |
| AND Grow International Limited | Professional & scientific | 2022 |
| Anders Pro Valeting (APV) Ltd | Wholesale & retail | 2017 |
| Anderson Plumbers Limited | Construction | 2020 |
| Andover Market Traders Limited | Administrative & support | 2003 |
| Andreas Stihl Limited | Wholesale & retail | 1978 |
| Andrew Malcolm Limited | Professional & scientific | 2017 |
| Andrews & Co Improvements Ltd | Construction | 2022 |
| Andrius Consulting Limited | Information & communication | 2025 |
| Andy Butler Consulting Limited | Professional & scientific | 2023 |
| Andy Quin Music Ltd | Information & communication | 2025 |
| Andy Sims Ltd | Households | 2022 |
| Anewan Limited | Professional & scientific | 2024 |
| Angela Whitty Enterprises Limited | Information & communication | 2024 |