| Algonee Limited | Information & communication | 2015 |
| Ali's Wokingham Limited | Hospitality | 2018 |
| Align & Flow Limited | Arts & recreation | 2025 |
| Alis Mart Ltd | Wholesale & retail | 2021 |
| Aliseni Holding Ltd | Financial services | 2026 |
| Alive IT Consultancy Ltd | Information & communication | 2011 |
| ALL Bespoke by Simon Dowling Ltd | Wholesale & retail | 2023 |
| ALL Builds (Berkshire) Ltd | Construction | 2012 |
| ALL Clean Restoration Limited | Administrative & support | 2023 |
| ALL Occasion Flowers Ltd | Wholesale & retail | 2019 |
| Allbluemass Ltd | Information & communication | 2024 |
| Allegro Finance Limited | Financial services | 2024 |
| Allen Consulting Limited | Professional & scientific | 2006 |
| Allensons Mortgage Advisors Limited | Financial services | 2001 |
| Alleyne Design Ltd | Extraterritorial | 2024 |
| Allfolio Property Ltd | Real estate | 2025 |
| Alliance Accounting Services Ltd | Professional & scientific | 2024 |
| Alliance Motors & Body Repairs Ltd | Manufacturing | 2012 |
| Alloro Restaurants Ltd | Hospitality | 2019 |
| Allternet Limited | Professional & scientific | 2015 |
| Alluri Estates Limited | Real estate | 2024 |
| Ally Barrow Ltd | Professional & scientific | 2023 |
| Allyson Grace Limited | Health & social care | 2021 |
| Alma Court Management Company Limited | Households | 1972 |
| Alnico Ltd | Professional & scientific | 2019 |
| Alore Accounting Limited | Professional & scientific | 2020 |
| Alpha Flying Limited | Arts & recreation | 1981 |
| Alpha Helix Limited | Professional & scientific | 2015 |
| Alpha RHO NU Ltd | Real estate | 2026 |
| Alphablocks Limited | Information & communication | 2010 |
| Alphaland Ltd. | Arts & recreation | 1998 |
| Alphanet Limited | Wholesale & retail | 1994 |
| Alpine Retreat Ltd | Other services | 2018 |
| ALS Global Solution Limited | Transport & logistics | 2022 |
| ALT BI Consultancy Limited | Professional & scientific | 2023 |
| Alternatives (GB) Limited | Professional & scientific | 2011 |
| Altimetrik UK Ltd | Information & communication | 2021 |
| Alton & Jones Heating Solutions Ltd | Construction | 2023 |
| Altuena Limited | Administrative & support | 2021 |
| ALW IMP Pharma Ltd. | Professional & scientific | 2014 |
| Always & Beyond Limited | Health & social care | 2024 |
| AM Homecare Services Ltd | Health & social care | 2023 |
| AM Move Ltd | Manufacturing | 2025 |
| Am-Spotless Cleaning Ltd | Administrative & support | 2024 |
| AM2PM Fitness Ltd | Administrative & support | 2023 |
| AMA Concepts Limited | Administrative & support | 2017 |
| Amaraayaz Limited | Other services | 2017 |
| Ambanja Pictures Limited | Information & communication | 2011 |
| Ambarrow Courtyard Management Limited | Households | 1995 |
| Amber Tax & Accounting Ltd | Professional & scientific | 2025 |
| Amberlodge Limited | Arts & recreation | 1972 |
| Ambition Creative Limited | Information & communication | 2008 |
| AMC Lets Limited | Real estate | 2026 |
| AMD Technologies Limited | Information & communication | 2015 |
| Amenity Warehouse Limited | Wholesale & retail | 2019 |
| American Amusements Limited | Arts & recreation | 1997 |
| American Amusements Property Limited | Real estate | 2005 |
| Amesbury Locks Limited | Manufacturing | 2012 |
| Ameya Realty Ltd | Real estate | 2024 |
| AMF Events Ltd | Professional & scientific | 2015 |
| AMF Ventures Limited | Financial services | 2002 |
| AMG Bathroom & Plumbing Services Limited | Construction | 1996 |
| AMH Admin Limited | Administrative & support | 2003 |
| AMH Workwear Ltd | Wholesale & retail | 2024 |
| Amicus VMS Limited | Construction | 2003 |
| Amitek Limited | Information & communication | 2013 |
| Amkris Consulting Limited | Information & communication | 2018 |
| AMO United Kingdom Limited | Manufacturing | 2002 |
| Amogh Technologies Limited | Information & communication | 2014 |
| Amors Auto Solutions Limited | Wholesale & retail | 2011 |
| AMR Data Management Services Ltd | Information & communication | 2012 |
| Amro Kitchens Ltd | Wholesale & retail | 2022 |
| Amrut Solutions Limited | Information & communication | 2015 |
| AMY Bartlett Training Limited | Health & social care | 2023 |
| Amyra & Co Properties Ltd | Real estate | 2021 |
| AMZ Auto Services Ltd | Wholesale & retail | 2025 |
| ANA Cars Sales Limited | Manufacturing | 2024 |
| Anagag Ltd | Professional & scientific | 2012 |
| Analytical Intelligence Ltd | Administrative & support | 2024 |
| Anderson Aviation Limited | Transport & logistics | 2017 |
| Anderson Contractors Limited | Construction | 2001 |
| Anderson Enterprises Limited | Wholesale & retail | 2017 |
| Anderson Homes Limited | Agriculture & fishing | 2017 |
| Andi Vehicle Services Ltd | Wholesale & retail | 2013 |
| Andl Consulting Ltd | Professional & scientific | 2020 |
| Andrade Smith and SON LLP | | 2011 |
| Andralex Limited | Professional & scientific | 2022 |
| Aneela Hoey Limited | Wholesale & retail | 2024 |
| Anelvey Marketing Limited | Professional & scientific | 2010 |
| Angel Beauty Lounge Ltd | Other services | 2024 |
| Angel Outpost Ltd | Information & communication | 2018 |
| Angel Tree Homes Limited | Real estate | 2019 |
| Anisha Osbourne Consulting Limited | Professional & scientific | 2024 |
| Anjani Private Ltd | Information & communication | 2024 |
| Anjish Estates Ltd | Real estate | 2023 |
| Ankh Developments Ltd | Real estate | 2021 |
| Annabel Kaur Ltd | Professional & scientific | 2020 |
| Anneshon Ltd | Wholesale & retail | 2024 |
| Annette Power Limited | Other services | 2011 |
| Ansintell Advisory Ltd | Professional & scientific | 2025 |