| Birch Farm Plastics Ltd | Water & waste | 2019 |
| Birchwood Software Consultancy Ltd | Information & communication | 2025 |
| Birla Holdings Ltd | Other services | 2023 |
| BK Retailers Ltd | Wholesale & retail | 2022 |
| Black & Gold Ventures Ltd | Wholesale & retail | 2019 |
| Black Circle Holdings (Swansea) Limited | Administrative & support | 2014 |
| Black Circle Retail Design Ltd | Administrative & support | 2013 |
| Black Oak Motor Company Ltd | Wholesale & retail | 2022 |
| Blackwell Enginering Limited | Construction | 2019 |
| Blakes Popcorn Limited | Hospitality | 2019 |
| Blas Glas CYF | Information & communication | 2025 |
| Blodau Training Ltd | Education | 2020 |
| Blue 360 Limited | Professional & scientific | 2021 |
| Blue Diamond Swansea Limited | Hospitality | 2021 |
| Bluebellandbrambles Ltd | Wholesale & retail | 2026 |
| Bluefreds Limited | Other services | 2017 |
| Bluejacket Firearms Ltd. | Wholesale & retail | 2017 |
| Bluesky Software and Solutions Ltd | Information & communication | 2003 |
| BM Investments Ltd | Construction | 2025 |
| Boba & Tempura Ltd | Hospitality | 2026 |
| Boiler Boyz (South Wales) Limited | Construction | 2026 |
| Bond Mortgage Services Ltd | Financial services | 2018 |
| Booths by the Bridge Ltd | Hospitality | 2024 |
| Booze Express Ltd | Wholesale & retail | 2015 |
| Booze Express Neath Limited | Wholesale & retail | 2020 |
| Boran Ltd | Other services | 2019 |
| Boss Building Contractors Ltd | Construction | 2023 |
| Boss Skips Ltd | Water & waste | 2025 |
| Boston Barberz Ltd | Other services | 2025 |
| BOW WOO Ltd | Other services | 2025 |
| Bowen's Lettings Ltd | Real estate | 2018 |
| BPE Contractors Limited | Energy | 2024 |
| Bravegate Limited | Wholesale & retail | 1980 |
| Bravemore Limited | Health & social care | 1984 |
| Breconview Meats Ltd | Wholesale & retail | 2017 |
| Brew&Co Limited | Hospitality | 2024 |
| Brightlook Limited | Professional & scientific | 1990 |
| Brightside Smoking Limited | Wholesale & retail | 2014 |
| Brilliant Hand Car Wash Ltd | Administrative & support | 2024 |
| Brit Circuit Ltd | Information & communication | 2014 |
| Briton Ferry (Shipping Services) Limited | Real estate | 1993 |
| Briton Ferry Brewing Company Limited | Wholesale & retail | 2016 |
| Briton Ferry Llansawel Limited | Arts & recreation | 2023 |
| Briton Ferry Steel Cricket Club Ltd | Arts & recreation | 2026 |
| Briton Ferry Stevedoring Limited | Transport & logistics | 2003 |
| Briton Ferry Town Sports Association | Arts & recreation | 2003 |
| Bronwen Lodges Ltd | Hospitality | 2022 |
| Broomfield & Alexander Wealth Management Ltd | Financial services | 2011 |
| Bryant Mediation Services Limited | Professional & scientific | 2025 |
| Bryn Newydd Colliery Company Limited | Mining & quarrying | 1966 |
| Bryndulais Inn Limited | Hospitality | 2007 |
| Bryndulais Scaffolding Limited | Administrative & support | 2012 |
| Bryngold Books Limited | Information & communication | 2004 |
| BTP Properties Limited | Real estate | 2023 |
| Bubble Platforms Limited | Information & communication | 2026 |
| Buddytracker Ltd | Information & communication | 2025 |
| Buffoon Media Limited | Manufacturing | 2010 |
| Building Bonds Ltd | Education | 2014 |
| Building Opportunities Learning Disabilities Ltd | Public administration | 2024 |
| Bullybottomrail Supply Limited | Construction | 2020 |
| Bumps & Scuffs Car Care Ltd | Wholesale & retail | 2015 |
| BUN Intended Ltd | Hospitality | 2025 |
| Burnant Shooting Ground Limited | Extraterritorial | 2006 |
| Buttons Property Ltd | Real estate | 2021 |
| Buy ANY Motor Limited | Wholesale & retail | 2017 |
| Buzzbox Creative Limited | Professional & scientific | 2008 |
| Bythesea Solutions Ltd | Information & communication | 2013 |
| C & C Stores Limited | Wholesale & retail | 2017 |
| C & P Building Contractors Ltd | Construction | 2022 |
| C & R Solutions Wales Limited | Construction | 2024 |
| C J ENT UK Ltd | Manufacturing | 2015 |
| C J George Limited | Hospitality | 2023 |
| C J Motors Ltd | Wholesale & retail | 2023 |
| C&G Home Improvements Ltd | Manufacturing | 2020 |
| C&S Engineering Ltd | Professional & scientific | 2025 |
| C&T Eco Consultants Ltd | Construction | 2014 |
| C-Nic Consultants Ltd | Education | 2025 |
| C. & S. (Neath) Steel Services Limited | Manufacturing | 1979 |
| C. & S. (Port Talbot) Limited | Manufacturing | 1959 |
| C. & S. Holdings South Wales Limited | Financial services | 2020 |
| C. Moses Roofing Limited | Construction | 1982 |
| C.A.J. Fielding Engineering Services Ltd | Construction | 2013 |
| C.C.S. Neath Electrics Limited | Construction | 1977 |
| C.M.F. (West) Solid Fuel Centre Limited | Administrative & support | 1970 |
| C.T. Lewis Ltd | Transport & logistics | 2001 |
| Caboome Limited | Information & communication | 2020 |
| Cadarn Information Security Limited | Information & communication | 2026 |
| Cadence Interiors Ltd | Construction | 2009 |
| Cadoxton Community Leisure Limited | Arts & recreation | 2019 |
| Caer Hendy Gardens Limited | Construction | 2005 |
| CAFE46 Ltd | Hospitality | 2024 |
| CAH Ltd | Construction | 1999 |
| Cake Academy Wales Limited | Hospitality | 2017 |
| Cakes Across the Way Ltd | Manufacturing | 2026 |
| Calan Accountants Ltd | Extraterritorial | 2023 |
| Calan DVS | Hospitality | 2011 |
| Caled Bricklaying Ltd | Construction | 2025 |
| Call of the Wild (Development) Limited | Professional & scientific | 1998 |
| Call of the Wild (Holdings) Ltd | Professional & scientific | 2020 |
| Calo Estates Limited | Real estate | 2019 |