| Athina Medical Limited | Health & social care | 2013 |
| Atkinson & Kirby Limited | Manufacturing | 1926 |
| Atlantic Hardware Ltd | Manufacturing | 2009 |
| Atlas Northwest Ltd | Professional & scientific | 2014 |
| Atoll Diving Maldives Ltd | Administrative & support | 2022 |
| Atomica Digital Marketing Ltd | Professional & scientific | 2024 |
| Atpbadger Ltd | Professional & scientific | 2015 |
| ATR Property Group Limited | Real estate | 2026 |
| Aubit Computing Limited | Information & communication | 1995 |
| Auralithix Ltd | Information & communication | 2025 |
| Aureve Limited | Manufacturing | 2024 |
| Aurielle Aesthetics Ltd | Health & social care | 2021 |
| Austin Property Group Limited | Construction | 2025 |
| Austin.P Limited | Health & social care | 2020 |
| Autodoorfix Limited | Construction | 2025 |
| Autokit Tyre Services Limited | Wholesale & retail | 2013 |
| Automotive Training Academy Ltd | Education | 2022 |
| Autoshine North Wales Ltd | Administrative & support | 2024 |
| Autozen Wrexham Ltd | Wholesale & retail | 2024 |
| Autumn Leaves Holdings Ltd | Financial services | 2021 |
| AV Garage Services Ltd | Wholesale & retail | 2026 |
| Ava-Tan Sunbeds and Services Ltd | Construction | 2025 |
| Avasin Cafe Ltd | Hospitality | 2026 |
| Avery Group Ltd | Households | 2018 |
| Avery Productions Ltd | Extraterritorial | 2022 |
| Avista Properties Ltd | Real estate | 2008 |
| Avium Studios UK Ltd | Information & communication | 2025 |
| AVL Builders Ltd | Construction | 2025 |
| Avnp Limited | Professional & scientific | 2025 |
| Avondale Plastering Services Ltd | Construction | 2016 |
| AWB Plastics Limited | Manufacturing | 2008 |
| Awdf Properties Limited | Real estate | 2023 |
| AWE Environmental Services Ltd | Manufacturing | 2019 |
| Awel Cymru Gogledd CIC | Arts & recreation | 2024 |
| Awgts Limited | Construction | 2016 |
| Axigma Limited | Wholesale & retail | 2025 |
| Axiotech Automation Limited | Professional & scientific | 2014 |
| Axis Medical Group Ltd | Health & social care | 2023 |
| Axis NDT Limited | Professional & scientific | 2019 |
| Ayodeji Kimlly Limited | Transport & logistics | 2025 |
| AYS Travels Ltd | Transport & logistics | 2023 |
| Aztec Prime Consulting Limited | Information & communication | 2016 |
| B H Heating Services Limited | Construction | 2022 |
| B Homecare & Co Ltd | Health & social care | 2023 |
| B J Clarke Limited | Transport & logistics | 2012 |
| B Street Social Limited | Hospitality | 2018 |
| B&B Furniture Retail Ltd | Wholesale & retail | 2026 |
| B&B UK Investments Ltd | Real estate | 2026 |
| B&D Electrical Services Limited | Construction | 2006 |
| B&N Engineering Limited | Manufacturing | 2019 |
| B'Division Limited | Wholesale & retail | 2019 |
| B. Paletta Limited | Wholesale & retail | 2005 |
| B.B Entertainment Ltd | Hospitality | 2026 |
| B.S. & R. Price (Developers) Limited | Professional & scientific | 1980 |
| B.S. & R. Price (Properties) Limited | Real estate | 1963 |
| BA Nigel Limited | Administrative & support | 2015 |
| BAA BAA Design Limited | Professional & scientific | 2003 |
| Bababalloonist Ltd | Information & communication | 2026 |
| Baby Cloud Group Ltd | Education | 2022 |
| Bace Facilities Group Ltd | Professional & scientific | 2021 |
| Bace Training Ltd | Education | 2025 |
| BAD Apple Beers Ltd | Hospitality | 2023 |
| Baden Health Ltd | Health & social care | 2026 |
| Badshahi Khan Limited | Wholesale & retail | 2025 |
| Bailaby Projects Limited | Administrative & support | 2010 |
| Baker Builders Limited | Construction | 2018 |
| Baker Scaffolding Limited | Construction | 2006 |
| Baker Surgical Limited | Health & social care | 2010 |
| Baldini Properties Limited | Construction | 2008 |
| Baleeria One Ltd | Real estate | 2015 |
| Balmuir Garage Limited | Wholesale & retail | 2025 |
| Bambini Childminding Ltd | Health & social care | 2017 |
| Bambino Babies Ltd | Health & social care | 2023 |
| Bamboo LUO Limited | Hospitality | 2025 |
| Bames Ltd | Manufacturing | 2020 |
| Bamfords Executive Chauffeur Services Limited | Transport & logistics | 2025 |
| Banana Bens Ltd | Hospitality | 2019 |
| Bangor-On-Dee Races Limited | Arts & recreation | 1987 |
| Bank Farm Honey Company Limited | Agriculture & fishing | 2025 |
| Bank Top Management Company Limited | Real estate | 2017 |
| Bant Dental Laboratory Limited | Health & social care | 2017 |
| Baps Food Ltd | Hospitality | 2022 |
| Barberbars Ltd | Hospitality | 2019 |
| Barclub Ltd | Hospitality | 2026 |
| Bardonrich Ltd | Hospitality | 2015 |
| Bargain Trend Limited | Wholesale & retail | 2016 |
| Barlows MOT Station Ltd | Wholesale & retail | 2018 |
| Barnes Cooper Limited | Professional & scientific | 2008 |
| Barnes Enterprises Group Limited | Professional & scientific | 2025 |
| Barnes Stitch Studio Limited | Other services | 2026 |
| Barnett Engineering Limited | Manufacturing | 1989 |
| Barnwood Management Limited | Other services | 1993 |
| Barriga Mcdonald Solicitors Limited | Professional & scientific | 2011 |
| Bart & 4 Dogs Ltd | Hospitality | 2023 |
| Bart & the Horse & Jockey Ltd | Hospitality | 2024 |
| Barton - Fancott & Streatly Consultants Ltd | Construction | 2007 |
| Barwise Commercial Ltd | Financial services | 2023 |
| Basc Direct Limited | Other services | 2014 |
| Basc Limited | Other services | 2003 |
| Basea Limited | Wholesale & retail | 2024 |