| Bater Bar and Restaurant Services Ltd | Hospitality | 2023 |
| Battle Nexus the Hobby Centre Ltd | Wholesale & retail | 2025 |
| Bayliss Projects Ltd | Real estate | 2020 |
| BC and MA Foods Ltd | Hospitality | 2025 |
| Bcma Properties Limited | Real estate | 2022 |
| Beach Training Specialist (BTS) Solutions Limited | Education | 2013 |
| Beak Elevated Limited | Health & social care | 2024 |
| Beastly Media (TGC2) Ltd | Information & communication | 2025 |
| Beastly Media Ltd | Information & communication | 2020 |
| Beau Transport Limited | Transport & logistics | 2025 |
| Beautiful Blinds Curtains Interiors Ltd | Wholesale & retail | 2018 |
| Beauty and Perfection Salon Limited | Other services | 2017 |
| Bedwas Gymnastics Club CIC | Arts & recreation | 2014 |
| Bedwas Rising Stars Childcare Ltd | Health & social care | 2022 |
| Bedwas Rugby 2011 Limited | Arts & recreation | 2011 |
| Bedwasrock Ltd | Wholesale & retail | 2002 |
| Beech Farm Meats Limited | Wholesale & retail | 2015 |
| Belief Sports Ltd | Wholesale & retail | 2011 |
| Bellium Healthcare Limited | Administrative & support | 2020 |
| Belly Scratch Productions Ltd | Arts & recreation | 2018 |
| BEN Isaac Accounting Limited | Professional & scientific | 2025 |
| Benchmark (G.B) Limited | Construction | 2024 |
| Benchmark Scenic Construction Ltd | Manufacturing | 2018 |
| Bertrey Limited | Information & communication | 2004 |
| Best FIX Construction Ltd | Construction | 2024 |
| Beth Williams Photography Ltd | Hospitality | 2022 |
| Beton Bauen Limited | Construction | 2006 |
| Beyond Plastic Global Limited | Information & communication | 2020 |
| BIA Energy Consulting Limited | Professional & scientific | 2019 |
| Big and Small Groundcare Ltd | Administrative & support | 2023 |
| Big Budda Fish & Chips 2 Ltd | Hospitality | 2025 |
| Big Budda Fish & Chips Ltd | Hospitality | 2025 |
| Big Orange Events Limited | Arts & recreation | 2026 |
| Bike Shredz Ltd | Wholesale & retail | 2016 |
| Billingham Holdings Ltd | Extraterritorial | 2015 |
| Biological Preparations Group Limited | Financial services | 2014 |
| Biological Preparations Limited | Professional & scientific | 2008 |
| Birds Properties Limited | Real estate | 2025 |
| Bishop Bayliss Developments (Cardiff Gate) Limited | Construction | 2024 |
| Bison BLU Limited | Information & communication | 2026 |
| Biswg Limited | Other services | 2009 |
| BJM Property Ltd | Real estate | 2013 |
| Black Eight Housing Ltd | Real estate | 2020 |
| Blackbrook Sporthorses Limited | Agriculture & fishing | 2020 |
| Blackcountry Taverns Ltd | Hospitality | 2022 |
| Blackice Trading Ltd | Wholesale & retail | 2013 |
| Blackwood 4X4 Limited | Wholesale & retail | 2025 |
| Blakeon Haulage Ltd | Professional & scientific | 2024 |
| Blakeon Living Spaces Ltd | Construction | 2020 |
| Blonde Sheep Licensing Limited | Professional & scientific | 2015 |
| Bloomin Foods Ltd | Hospitality | 2022 |
| Blossom Early Years | Education | 2022 |
| Blue Diamonds Projects Limited | Wholesale & retail | 2024 |
| Blue Lagoon Arts C.I.C. | Arts & recreation | 2019 |
| Blue Property Holdings Ltd | Real estate | 2026 |
| Bluewave Telecom Limited | Information & communication | 2022 |
| BNE Brickwork Ltd | Construction | 2025 |
| Bomper Studio Limited | Administrative & support | 2014 |
| BON Homie Drinks Ltd | Manufacturing | 2024 |
| Bond Demolition Ltd | Construction | 1999 |
| Bond Technology Ltd | Information & communication | 2020 |
| Bookback Ltd | Information & communication | 2026 |
| Boomerang Dogs Ltd | Other services | 2021 |
| Boomerang Property Investments Limited | Real estate | 2013 |
| Borne Consult Limited | Professional & scientific | 2022 |
| Bossy Lashes Limited | Other services | 2020 |
| Bothware Ltd | Information & communication | 2003 |
| Botifiller Limited | Real estate | 2018 |
| Bowquila Ltd | Hospitality | 2023 |
| Boxmag-Rapid Limited | Professional & scientific | 2001 |
| Bradvale Limited | Construction | 1993 |
| Brathiad O Fywyd Ltd | Health & social care | 2026 |
| Breathtaking Communication Ltd | Professional & scientific | 2024 |
| Brew Monster Limited | Professional & scientific | 2017 |
| Brickcraft Construction Limited | Real estate | 2009 |
| Bricla Management Limited | Real estate | 2012 |
| Bridget Frances Rashid Limited | Extraterritorial | 2022 |
| Briers Property Limited | Real estate | 2016 |
| Bright Sparx Electrical Pontypool Limited | Construction | 2022 |
| Brinsons Limited | Real estate | 2006 |
| Brixley Limited | Information & communication | 2006 |
| Broadoak International Investments Limited | Construction | 2005 |
| Broughton Leys Management Company Limited | Administrative & support | 2002 |
| Bryn Meadows Properties Limited | Real estate | 2008 |
| BSC Tools Limited | Manufacturing | 2021 |
| Bsides OT UK CIC | Administrative & support | 2025 |
| BTX Accountancy Solutions Ltd | Professional & scientific | 2022 |
| Bubbles Domestic Services Ltd | Administrative & support | 2025 |
| Bucket List Adventure Travel Limited | Administrative & support | 2017 |
| Budget Motors Caerphilly Limited | Wholesale & retail | 2021 |
| Building Communities Trustee Limited | Administrative & support | 2014 |
| Building Management Solutions Limited | Construction | 2002 |
| Buln Ltd | Construction | 2025 |
| Bumford Electrical Limited | Construction | 2020 |
| Bursali Towels (UK) Limited | Wholesale & retail | 2005 |
| Bush Whacka Limited | Administrative & support | 2016 |
| Busi-Man Services LP | | 2017 |
| Busy Bees Property Services Limited | Construction | 2016 |
| Butterfly Publishing Limited | Information & communication | 2025 |
| Buttys Bakery Ltd | Manufacturing | 2026 |