| Bahia Beauty and Hair Ltd | Other services | 2023 |
| Bailey Wright Photography Limited | Professional & scientific | 2025 |
| Baileys Property Development Ltd | Construction | 2019 |
| Baitiwu Ltd | Wholesale & retail | 2025 |
| Baker Ashley Limited | Professional & scientific | 2017 |
| Bakestones Ltd | Manufacturing | 2024 |
| Balance Chiropractic and Wellness Ltd | Health & social care | 2019 |
| Bambinos Nurseries Ltd | Health & social care | 2019 |
| Banh MI Army Ltd | Hospitality | 2026 |
| Bar - Beverages and Entertainment Ltd | Hospitality | 2024 |
| Bar Pro Events Ltd | Manufacturing | 2022 |
| Barod Homes Ltd | Construction | 2026 |
| Barod Plumbing & Heating Ltd | Construction | 2023 |
| Barrie Holden Ltd. | Wholesale & retail | 2022 |
| Barrie Williams Developments Ltd | Construction | 1990 |
| Barrier Medical Ltd | Manufacturing | 2024 |
| Baseline Restoration Ltd | Health & social care | 2012 |
| BBB51T Limited | Information & communication | 2025 |
| BBI Consultants Ltd | Professional & scientific | 2025 |
| BD Vincent Property Limited | Construction | 2025 |
| BDP Accountants Ltd | Professional & scientific | 2024 |
| BE Designs & Technical Ltd | Information & communication | 2022 |
| BE Your Best Academy Ltd | Professional & scientific | 2025 |
| Beacons Business Network Ltd | Other services | 2023 |
| Bear Press Ltd | Information & communication | 2017 |
| Beaufort Commercial Property Ltd | Real estate | 2013 |
| Beddau Motors Ltd | Wholesale & retail | 2025 |
| Beingwell YNG Nghymru CIC | Education | 2025 |
| Bekoz Transport Ticketing Ltd | Manufacturing | 2018 |
| Bela Curi Limited | Transport & logistics | 2026 |
| Bella Nails Bar Ltd | Other services | 2025 |
| Belscan Limited | Administrative & support | 1986 |
| BES Commercial Maintenance Limited | Construction | 2014 |
| Bespoke Flooring Studio Limited | Wholesale & retail | 2018 |
| Best Kebab Ponty Ltd | Hospitality | 2026 |
| Best Square Kebab, Pizza & Burger Limited | Hospitality | 2026 |
| Best Square Pizza & Burger Ltd | Hospitality | 2025 |
| Bettabuys Hardware Limited | Wholesale & retail | 2015 |
| Betty C LLP | | 2011 |
| Between the Trees Limited | Arts & recreation | 2018 |
| Bevans Quality Meats Ltd | Manufacturing | 1980 |
| Bewsh Ltd | Wholesale & retail | 2019 |
| Beyond Developments Ltd | Real estate | 2023 |
| Beyond the CV Limited | Administrative & support | 2025 |
| Big Bear Blondies Ltd | Wholesale & retail | 2025 |
| Bigbing Holdings Limited | Information & communication | 2021 |
| Bigfoot Arts Education (South Wales) Ltd | Education | 2007 |
| Bioha Laboratories Group Ltd | Manufacturing | 2015 |
| Birkemp Limited | Construction | 2000 |
| Bitwerx Ltd | Information & communication | 2022 |
| BJJ Caerphilly Limited | Education | 2025 |
| BJL Welding Limited | Manufacturing | 2023 |
| BK Best Kebab Ltd | Hospitality | 2024 |
| BL - Penarth Ltd | Hospitality | 2024 |
| Black Box Advisory Ltd | Professional & scientific | 2019 |
| Black Forest Forest & Garden Ltd | Agriculture & fishing | 2015 |
| Black Maverick Investments Ltd | Financial services | 2022 |
| Black Mountains DC Ltd | Health & social care | 2026 |
| Blackpool Beauty UK Ltd | Wholesale & retail | 2025 |
| Blacks Engineering Limited | Construction | 2024 |
| Blaenbran Equine Limited | Agriculture & fishing | 2021 |
| Blinghair Fashion Company Ltd | Wholesale & retail | 2025 |
| Blinktex Fashion Ltd. | Manufacturing | 2024 |
| Blissful Life Global Ltd | Wholesale & retail | 2025 |
| Blizz Clothing Ltd | Wholesale & retail | 2016 |
| Bloomin' Marvellous Ltd | Administrative & support | 2019 |
| Blooming Vitality Ltd | Other services | 2026 |
| Blooms "R" US Limited | Wholesale & retail | 2003 |
| Blossom Family Contact Services Limited | Health & social care | 2022 |
| Blue Sky 07 Ltd | Hospitality | 2025 |
| Blue Square Alliance Ltd | Real estate | 2013 |
| Blue Water Recruitment Limited | Administrative & support | 2010 |
| BM Energy Solutions Limited | Construction | 2025 |
| BMA Construction South Wales Limited | Construction | 2025 |
| BOB GAY Plant Hire Limited | Administrative & support | 2018 |
| Body Luxuries Limited | Wholesale & retail | 2025 |
| Boilersure Heating Limited | Construction | 2025 |
| Bondoffer Ltd | Real estate | 2012 |
| Boothman Property Limited | Real estate | 2021 |
| Border Storage & Warehousing Limited | Professional & scientific | 2011 |
| Borma Bakes Ltd | Manufacturing | 2026 |
| Bosley Cleaning Services Limited | Administrative & support | 2018 |
| Bosley Property Maintenance Services Limited | Administrative & support | 2022 |
| Bossa Nova Beers Limited | Wholesale & retail | 2014 |
| Bosuy Limited | Wholesale & retail | 2025 |
| Botaneg Ltd | Wholesale & retail | 2022 |
| Bowden Dethridge Limited | Professional & scientific | 2015 |
| Bowden Dethridge Properties Limited | Real estate | 2025 |
| Box Planet Limited | Manufacturing | 2008 |
| Bradley Morgan Fashion Ltd | Wholesale & retail | 2025 |
| Bramble Construction Bridgend Ltd | Construction | 2002 |
| Braxini's Limited | Hospitality | 2025 |
| Brecon DC Ltd | Health & social care | 2014 |
| Brent Davies Consultancy Limited | Administrative & support | 2015 |
| Brett Davies Limited | Mining & quarrying | 2019 |
| Brice Jones Consulting Ltd | Professional & scientific | 2025 |
| Bricks and Morgan Ltd | Construction | 2022 |
| Bridgend Carpet Binding Services Limited | Wholesale & retail | 2024 |
| Bridgend Floorstyle Limited | Wholesale & retail | 2004 |
| Bridgend Scaffolding Limited | Construction | 2019 |