| Bright Seam Limited | Information & communication | 2012 |
| Brightseed Development Ltd | Information & communication | 2015 |
| Brightview Accountancy LLP | | 2025 |
| Brilliant Driving School UK Ltd | Education | 2022 |
| Brinjal Indian Diner (Swansea) Ltd | Wholesale & retail | 2016 |
| Brisco Hire Services Limited | Extraterritorial | 1980 |
| Brisco Truck Rental Limited | Administrative & support | 1980 |
| Brisco Waste Disposal Limited | Other services | 1980 |
| Brisco Williams & Sons Limited | Other services | 1976 |
| Brisco Williams (GAS) Limited | Other services | 1980 |
| Brisco Williams (Shareholder) Limited | Financial services | 2024 |
| Bristol Channel Swimming Ltd | Public administration | 2022 |
| Bristol Civils Ltd | Construction | 2021 |
| Bristol Live Magazine Ltd | Information & communication | 2015 |
| Bristol Steel Stockholders Limited | Wholesale & retail | 1976 |
| Brit Blend Ltd | Wholesale & retail | 2019 |
| Britannia Commercial Brokers Ltd | Financial services | 2015 |
| Britannia Inn (Gower) Limited | Hospitality | 2006 |
| Britannia Towbars Ltd | Wholesale & retail | 2010 |
| Briton Ferry Childcare Limited | Health & social care | 2016 |
| Briton Ferry Healthcare Limited | Wholesale & retail | 2023 |
| Briton Ferry Salvage Limited | Administrative & support | 2009 |
| BRM Physiques Ltd | Arts & recreation | 2024 |
| BRO Blade Barber Ltd | Other services | 2024 |
| Broadband UN Limited | Extraterritorial | 2013 |
| Broadmead Holdings Limited | Financial services | 2023 |
| Broadoak Conservatory Conversions Ltd | Construction | 2021 |
| Broadreach Integrity Ltd | Manufacturing | 2024 |
| Broadstone Construction (Swansea) Ltd | Construction | 2012 |
| Broadway Social Enterprise Limited | Other services | 2017 |
| Broadwood Cyber Security Services Limited | Information & communication | 2018 |
| Broawel MMR Ltd | Construction | 2025 |
| Bromham Leisure Limited | Arts & recreation | 1991 |
| Brook Innovations Ltd | Real estate | 2018 |
| Brook Mill Group Ltd | Financial services | 2023 |
| Brook Mill Property Ltd | Real estate | 2025 |
| Brookborough Trading Limited | Wholesale & retail | 2022 |
| Brookles Ltd | Manufacturing | 2020 |
| Brooklyn's Hospitality Ltd | Hospitality | 2026 |
| Brookman Fittings Limited | Wholesale & retail | 2018 |
| Brooks Property Group Ltd | Real estate | 2019 |
| Brookside Energy Consulting Limited | Professional & scientific | 2015 |
| Brooksmith Building Limited | Construction | 2024 |
| Brooksmith Properties Limited | Real estate | 2025 |
| Brookson (5084K) Limited | Administrative & support | 2007 |
| Brookson (5393P) Limited | Professional & scientific | 2007 |
| Brother Engineering Ltd | Manufacturing | 2009 |
| Brothers Cash & Carry Limited | Wholesale & retail | 2015 |
| Brothers Development Wales Ltd | Real estate | 2023 |
| Brothers Takeaway Ltd | Hospitality | 2018 |
| Brown Stone Ltd | Hospitality | 2025 |
| Brownhill Nurseries Limited | Agriculture & fishing | 1985 |
| Browning Medicolegal Associates Limited | Health & social care | 2016 |
| Browns Barbering Ltd | Other services | 2020 |
| BRP Capital Limited | Professional & scientific | 2022 |
| Brp-Uk Limited | Real estate | 2020 |
| BRS Jewellers Ltd | Wholesale & retail | 2025 |
| Bruant Ltd | Real estate | 2022 |
| Bruckland and Spencer Property Management Limited | Real estate | 2019 |
| Brunae Body UK Ltd | Wholesale & retail | 2026 |
| Bruneberg Management Ltd | Wholesale & retail | 2021 |
| Brush in Hand Spraying and Decorators Limited | Construction | 2008 |
| Bruv's Bar Limited | Hospitality | 2019 |
| Bryg Associates UK Limited | Professional & scientific | 2016 |
| Brylea Haulage (Swansea) Limited | Transport & logistics | 2016 |
| Bryn Farm Engineering Limited | Manufacturing | 2012 |
| Bryn Illtyd Care Home Ltd | Health & social care | 2025 |
| Brynawael 1964 Limited | Extraterritorial | 2014 |
| Bryncarlen Limited | Financial services | 2018 |
| Bryngelli Ltd | Financial services | 2015 |
| Brynglas Property Partners Ltd | Construction | 2025 |
| Brynhyfryd Car Sales Limited | Wholesale & retail | 2006 |
| Brynhyfryd Community Centre Limited | Education | 2024 |
| Bryniau Bach Ltd | Real estate | 2024 |
| Brynllan Ltd | Agriculture & fishing | 2002 |
| Brynmead Court Management Company Limited | Households | 2016 |
| Brynmill Coffee House Limited | Hospitality | 2024 |
| Brynmill Coffee Limited | Hospitality | 2016 |
| Brynmill Ground Rents Limited | Real estate | 2021 |
| Brynsiriol CYF | Professional & scientific | 2014 |
| Bryntirion (Block D) RTM Company Limited | Households | 2020 |
| Brynway Limited | Hospitality | 2013 |
| Brynymor Barbers Ltd | Other services | 2023 |
| Brynymor Digital Ltd | Manufacturing | 2003 |
| Brynymor Mailbox Limited | Manufacturing | 2015 |
| Brynymor Puffs Ltd | Wholesale & retail | 2025 |
| BS Prop Co Ltd | Financial services | 2022 |
| BSB Hair Ltd | Other services | 2023 |
| BSC (Swansea) Ltd | Professional & scientific | 2021 |
| BSL Decorations Ltd | Construction | 2023 |
| Bsquared Consulting Engineers Ltd | Professional & scientific | 2024 |
| BSR Dental Limited | Health & social care | 2023 |
| Btmc Group Limited | Transport & logistics | 2025 |
| Bucataria Bunicii Ltd | Hospitality | 2025 |
| Bucephalus Property Ltd | Households | 2023 |
| Buckland Hall Farms Limited | Real estate | 2020 |
| Buckmaster Batcup Architects Limited | Professional & scientific | 2004 |
| Bud&Bay General Store Ltd | Wholesale & retail | 2023 |
| Buddan Limited | Extraterritorial | 2016 |
| Buddug Y BYD Ltd | Information & communication | 2021 |