| Astrixx Limited | Health & social care | 2021 |
| AT Ceramics Ltd | Construction | 2010 |
| Atarah Mayhew Ltd | Information & communication | 2019 |
| Athelney Developments Limited | Financial services | 2024 |
| Athwal Group Holdings Limited | Professional & scientific | 2023 |
| Atlas Fitness Ltd | Arts & recreation | 2019 |
| Atlas Nine Nine Ltd | Administrative & support | 2025 |
| Atlas Talent Limited | Administrative & support | 2025 |
| Atom Heart Consulting Ltd | Professional & scientific | 2013 |
| Atom Systems Limited | Information & communication | 2008 |
| ATR Engineering Services Limited | Professional & scientific | 2024 |
| Atwell Construction Limited | Construction | 2016 |
| AU Graphic Ltd | Professional & scientific | 2023 |
| Auckland Court (Southsea) Management Limited | Households | 2007 |
| Audberna Ltd | Construction | 2020 |
| Audiolock.Net Limited | Information & communication | 2010 |
| Auger Media Technology Limited | Professional & scientific | 2021 |
| Augerrf Ltd | Information & communication | 2025 |
| August Clarke Ltd | Administrative & support | 2011 |
| Augusta Property Group Limited | Financial services | 2021 |
| Aura Popa Limited | Wholesale & retail | 2022 |
| Aurora Essentials Limited | Wholesale & retail | 2025 |
| Aurora Pacific Ltd | Wholesale & retail | 2021 |
| Authentic Building and Roofing Ltd | Construction | 2022 |
| Authors Reach Ltd | Information & communication | 2015 |
| Auto Forum Developments Limited | Other services | 1970 |
| Auto Tech MAX Ltd | Wholesale & retail | 2024 |
| Autocontact Limited | Professional & scientific | 2023 |
| Autodriveuk Limited | Professional & scientific | 2026 |
| Autogleam (Southampton) Limited | Other services | 2005 |
| Automate Everything Limited | Information & communication | 2019 |
| Automotive Accessories Limited | Professional & scientific | 2002 |
| Automotive Glass Ltd | Wholesale & retail | 2022 |
| Automotive Services International (U.K.) Limited | Professional & scientific | 1998 |
| AUTOTEK21 Limited | Professional & scientific | 2011 |
| Autumn Electrical Services Limited | Construction | 2010 |
| Av-Pro Services Ltd | Information & communication | 2019 |
| AVA Financial Limited | Professional & scientific | 2026 |
| AVA Louise Bridal Wear Limited | Wholesale & retail | 2015 |
| AVA Recreation Holdings Limited | Financial services | 2024 |
| AVA Recreation Limited | Arts & recreation | 2013 |
| Avalla Limited | Administrative & support | 2021 |
| Avalonage Limited | Arts & recreation | 2013 |
| Avante Tax Ltd | Professional & scientific | 2026 |
| Aviso Business Services Limited | Professional & scientific | 2009 |
| Avni SUB Ltd | Hospitality | 2023 |
| Avyaan SUB Ltd | Hospitality | 2024 |
| Avyaan Trading Limited | Wholesale & retail | 2024 |
| Awaaz FM Community Radio CIC | Extraterritorial | 2011 |
| Awardresin Ltd | Construction | 2017 |
| Away on Business Ltd | Hospitality | 2019 |
| Awesome Architectural Glazing Solutions Ltd | Construction | 2008 |
| Awlp Limited | Financial services | 2024 |
| Axamplify Ltd | Information & communication | 2025 |
| Axim Global Limited | Professional & scientific | 2014 |
| AY Plastering Limited | Construction | 2014 |
| AYA Smile Ltd | Health & social care | 2018 |
| Ayres Chiropractic Limited | Health & social care | 2006 |
| Azebabydream Ltd | Wholesale & retail | 2023 |
| Aztec Facilities Limited | Arts & recreation | 2002 |
| B & L a Jupe Limited | Other services | 2019 |
| B Goggin Limited | Wholesale & retail | 2016 |
| B K Wright Ltd | Manufacturing | 2019 |
| B M Eldridge Consultancy Ltd | Professional & scientific | 2026 |
| B MEW Limited | Construction | 2015 |
| B W Electrical & Energy Limited | Construction | 2012 |
| B&B Enterprises Limited | Real estate | 2021 |
| B&B Laundry Limited | Financial services | 2015 |
| B&Hvr Holdings Ltd | Financial services | 2010 |
| B&Q Foundation | Other services | 2019 |
| B&Q Limited | Wholesale & retail | 1970 |
| B&Q Properties Chesterfield Limited | Real estate | 2010 |
| B&Q Properties Farnborough Limited | Real estate | 2011 |
| B&Q Properties Limited | Real estate | 1999 |
| B&Q Properties New Malden Limited | Real estate | 2000 |
| B&Q Properties South Shields Limited | Real estate | 2010 |
| B&Q Properties Sutton-In-Ashfield Limited | Real estate | 2011 |
| B&Q Properties Swindon Limited | Real estate | 2010 |
| B&Q Properties Witney Limited | Real estate | 2011 |
| B&Q Properties Wrexham Limited | Real estate | 2010 |
| B&S Carpentry Ltd | Construction | 2021 |
| B.Grange Holdings Limited | Financial services | 2025 |
| BA Yaldren Limited | Construction | 2019 |
| Baboo JI Drinks Company Ltd | Manufacturing | 2022 |
| Babooji South Limited | Hospitality | 2024 |
| Baby Squids East Hampshire Limited | Arts & recreation | 2021 |
| BABY2K.COM Limited | Wholesale & retail | 2006 |
| Babylon Hair Ltd | Other services | 2018 |
| Backi Ltd | Transport & logistics | 2012 |
| Baffi Coffee Company Ltd | Manufacturing | 2025 |
| Bahuchar Ltd | Wholesale & retail | 2022 |
| Baifield Fabrications Limited | Manufacturing | 2014 |
| Bainthorne Advisory Ltd | Extraterritorial | 2025 |
| Baird Associates Limited | Administrative & support | 2022 |
| Baker & Associates Ltd | Professional & scientific | 2013 |
| Bakers Arms 2019 Limited | Hospitality | 2019 |
| Balanced 4 U Ltd | Wholesale & retail | 2019 |
| BAM Media Marketing Ltd | Professional & scientific | 2021 |
| Bams Properties Ltd | Real estate | 2023 |
| Banister Grange RTM Company Ltd | Households | 2020 |