| Beacon Printers (Penarth) Limited | Manufacturing | 1972 |
| Bear PAK | Health & social care | 2008 |
| Bearmont Capital NO.3 Ltd | Real estate | 2025 |
| Bears Head Trading Company Ltd | Wholesale & retail | 2023 |
| Beauty Box (Cowbridge) Limited | Other services | 2022 |
| Beauty Box (Tenby) Limited | Other services | 2021 |
| Bekdo Holdings Ltd | Households | 2026 |
| Bellavista Care (Pontypridd) Limited | Health & social care | 2024 |
| Bellavista Care Centre Ltd | Health & social care | 2019 |
| Belle VUE Maintenance Ltd | Real estate | 2021 |
| Beprimed Limited | Professional & scientific | 2025 |
| Bernice Thomas Letting Limited | Real estate | 2025 |
| Beros Consulting Ltd | Professional & scientific | 2025 |
| Bespoke Goldsmith Ltd | Other services | 2019 |
| Betty Swallocks Limited | Hospitality | 2016 |
| Bevan - Mohaffel Locum Services Ltd | Health & social care | 2011 |
| Bhot Yoga Ltd | Arts & recreation | 2018 |
| Biarritz Ventures Ltd | Real estate | 2020 |
| Bias Property Limited | Real estate | 2006 |
| Big Bear Refrigeration Ltd | Manufacturing | 2021 |
| Big Love Music & Arts C.I.C. | Arts & recreation | 2020 |
| Big TJ International Limited | Wholesale & retail | 2019 |
| Biogen Architecture Ltd | Professional & scientific | 2018 |
| Black Eight Productions Ltd | Information & communication | 2021 |
| Black Ribbon Limited | Wholesale & retail | 2026 |
| Blackstone Partners Estate Planning Ltd | Professional & scientific | 2019 |
| Blake Interpreting Ltd | Professional & scientific | 2026 |
| Blank Space Productions Limited | Information & communication | 2010 |
| BLE MAE Films Limited | Information & communication | 2024 |
| Blenny Media Ltd | Information & communication | 2016 |
| Blossom With Sarah Ltd | Education | 2024 |
| BLU Sapphire Ltd | Hospitality | 2016 |
| Blue Bonbon Ltd | Wholesale & retail | 2022 |
| Blue Dragon Finance Ltd | Financial services | 2014 |
| Blue Moon Paint Services Limited | Manufacturing | 2017 |
| Bluewater CAD Ltd | Wholesale & retail | 2025 |
| Bocc Finance Limited | Financial services | 2021 |
| BOD Property Ltd | Real estate | 2025 |
| Boilertag Ltd | Information & communication | 2025 |
| Bolt Electrical Solutions Ltd | Construction | 2026 |
| Bolwell and Hayward Limited | Construction | 1979 |
| Bolwell and Hayward Properties Limited | Construction | 1988 |
| Bordeaux 12 Limited | Wholesale & retail | 2022 |
| Botham Williams Ltd | Real estate | 2022 |
| Bowden Jones Recruitment Ltd | Administrative & support | 2024 |
| Bowes Financial Services Ltd | Financial services | 2016 |
| Box Office Software Limited | Arts & recreation | 2013 |
| Brazil & Co Holdings Ltd | Financial services | 2025 |
| Brazil & Co Property Group Ltd | Households | 2020 |
| Bridge Accountants Limited | Professional & scientific | 2014 |
| Brighter Graphics Limited | Wholesale & retail | 2000 |
| Bristol Bakeries Ltd | Hospitality | 2024 |
| Britalia Door Products Limited | Manufacturing | 2004 |
| Britalia Doors Limited | Manufacturing | 2017 |
| Brito Media Limited | Information & communication | 2018 |
| Brittens Consulting Ltd | Education | 2026 |
| Brixtech Group Limited | Financial services | 2021 |
| Bron Y Glyn Company Limited | Households | 2012 |
| Brooklands Management Company Limited | Real estate | 1990 |
| Bryn Carw Ltd | Professional & scientific | 2023 |
| Bryn T Jones Cyfyngedig | Arts & recreation | 2013 |
| Bryte Ltd | Professional & scientific | 2020 |
| Btin Limited | Health & social care | 2023 |
| Burger Queen Ltd | Hospitality | 2025 |
| Burning Red Limited | Professional & scientific | 2007 |
| Business Continuity Management & Planning Limited | Professional & scientific | 2020 |
| Business News Wales Limited | Information & communication | 2015 |
| Butterworth Group Limited | Real estate | 2020 |
| Bwyta Bwyd Bombai (3B'S) Limited | Hospitality | 2016 |
| Byrdland Ltd | Real estate | 2018 |
| C L Richards Limited | Administrative & support | 2018 |
| C M Wall Design Services Limited | Professional & scientific | 2004 |
| C&L Lead Sheet Fabrication Limited | Manufacturing | 2011 |
| C.C. Properties Management Limited | Real estate | 2019 |
| Cabot Activated Carbon Holdings UK Limited | Financial services | 2012 |
| Cabot Activated Carbon UK Limited | Financial services | 2012 |
| Cabot Carbon Limited | Manufacturing | 1948 |
| Cabot G.B. Limited | Financial services | 1987 |
| Cabot Performance Materials UK Ltd. | Professional & scientific | 2011 |
| Cabot Plastics Limited | Financial services | 1977 |
| Cabot U.K. Limited | Financial services | 1980 |
| Cabot UK Holdings Limited | Financial services | 2000 |
| Cabs 64 Limited | Administrative & support | 2013 |
| Cadoc Castle Land Developments Limited | Real estate | 2004 |
| Cadre Advisory Holdings Limited | Financial services | 2014 |
| Cadre Advisory Limited | Professional & scientific | 2017 |
| Caerau Vale Trampoline Club Ltd | Arts & recreation | 2024 |
| Caio Properties Limited | Construction | 2019 |
| Cambrella Limited | Construction | 2023 |
| Cambrella Property Holdings Limited | Financial services | 2024 |
| Cambria Consulting Limited | Construction | 2011 |
| Cambria Property Holdings Limited | Real estate | 2013 |
| Cambrian Arts Limited | Wholesale & retail | 2000 |
| Cambrian Property Ltd | Real estate | 2018 |
| Candid Creative Studio Limited | Information & communication | 2014 |
| Canford Heath Holdings Limited | Financial services | 2026 |
| Canna Studio Ltd | Information & communication | 2018 |
| Canton Cross Motors Limited | Professional & scientific | 1993 |
| Capello Barbers City Centre Limited | Other services | 2025 |
| Capital Family Mediation Limited | Professional & scientific | 2014 |