| Briggs Interior Design Limited | Construction | 2020 |
| Bright Spark Group Limited | Construction | 2024 |
| Brighter Electrical Solutions Ltd | Construction | 2020 |
| Brilliant Textile Ltd | Wholesale & retail | 2024 |
| Brioso Agencies Limited | Wholesale & retail | 2012 |
| Britannis Limited | Information & communication | 2016 |
| Brixora Limited | Wholesale & retail | 2025 |
| Broadbent & Webb Limited | Professional & scientific | 2011 |
| Broadway Van Centre Limited | Wholesale & retail | 2007 |
| Broadwaypontypridd Ltd | Other services | 2016 |
| Brookfield Agriculture Ltd | Agriculture & fishing | 2025 |
| Brookhousecare Ltd | Health & social care | 2026 |
| Brown Bear Technology (UK) Ltd | Wholesale & retail | 2025 |
| Bryju Ltd | Construction | 2019 |
| Bryn Investments Limited | Financial services | 2021 |
| Brynmawr DC Ltd | Health & social care | 2023 |
| BS Medical Consultant Ltd | Wholesale & retail | 2020 |
| BS Renovations Limited | Real estate | 2019 |
| Bugsonabudget Ltd | Wholesale & retail | 2017 |
| Buildrite Roofrite Limited | Construction | 2017 |
| Bulbs Landscaping and Tree Services Limited | Agriculture & fishing | 2013 |
| Bullys Barbers Limited | Other services | 2011 |
| Bunch of Grapes Holdings Limited | Financial services | 2016 |
| Bunch of Grapes Restaurant and PUB Limited | Hospitality | 2016 |
| Bungalow Restaurant (Cardiff) Limited(The) | Real estate | 1968 |
| Butaran Limited | Information & communication | 2012 |
| Bvcl Ltd | Information & communication | 2015 |
| Bycudo Mobile-Private Chef Ltd | Hospitality | 2021 |
| C & L Windows Limited | Construction | 2018 |
| C a COX Pvcu Ltd | Construction | 2006 |
| C J Walton Properties Limited | Real estate | 2015 |
| C R Autos Limited | Wholesale & retail | 2018 |
| C S Phillips Property Developments Ltd | Construction | 2010 |
| C&Coleary Ltd | Real estate | 1988 |
| C. Williams Motor Company Limited | Professional & scientific | 2004 |
| C.B. Crook & Co. (Transport) Limited | | 1966 |
| C.G. Hygiene Services Limited | Health & social care | 2017 |
| C2 Interior Solutions Ltd | Construction | 2025 |
| Cabin Cwtch Limited | Hospitality | 2018 |
| Caerleon House Care 2024 Limited | Financial services | 2024 |
| Caerleon House Care Limited | Health & social care | 2020 |
| Cafe MAO Limited | Hospitality | 2002 |
| Cafelavista Limited | Wholesale & retail | 2018 |
| Cal's Flooring Solutions Ltd | Construction | 2025 |
| Caleb Private Company Limited | Health & social care | 2011 |
| Calibre Contracting Limited | Construction | 2003 |
| Calibre Equip Limited | Construction | 2014 |
| Calvitia Limited | Information & communication | 2024 |
| Camau Cyntaf I Ddysgu C.B.C | Professional & scientific | 2014 |
| Cambria Waste Solutions Ltd | Water & waste | 2023 |
| Cameron Properties SW Ltd | Real estate | 2026 |
| Campervan Hire Wales Limited | Administrative & support | 2022 |
| Cando Consultancy Services Limited | Professional & scientific | 2024 |
| Capel Rhondda Cyfyngedig | Other services | 2025 |
| Capel Y Tabernacl, CYF. | Other services | 2007 |
| Capital Property South Wales Ltd | Real estate | 2020 |
| Car Champ Ltd | Wholesale & retail | 2023 |
| Car Paint Experts Ltd | Wholesale & retail | 2020 |
| Carbelle Developments Ltd | Real estate | 2025 |
| Carbis Partnership Homes Ltd | Real estate | 2011 |
| Carbis Properties Limited | Construction | 1991 |
| Cardiff Bay Homes LLP | | 2014 |
| Cardiff Boating Limited | Extraterritorial | 2017 |
| Cardiff Construction Company Limited | Construction | 1981 |
| Cardiff Ground Specialists Ltd | Construction | 2019 |
| Cardiff Groundcare Limited | Administrative & support | 2011 |
| Cardiff Metropolitan Limited | Education | 2003 |
| Cardiff Research Solutions Ltd | Professional & scientific | 2020 |
| Cardiff Yachting Limited | Arts & recreation | 2017 |
| Cardiff/Glamorgan Metropolitan Limited | Education | 2003 |
| Care-Com Systems (SW) Ltd | Manufacturing | 2013 |
| Carl Lewis Carpentry & Drylining Ltd | Construction | 2023 |
| Caroline Rees Ltd | Education | 2018 |
| Carparms Limited | Hospitality | 2019 |
| Cartlab Ltd | Wholesale & retail | 2026 |
| Cartrefi Limited | Construction | 2017 |
| Carw CYF | Information & communication | 2016 |
| Castle Court Funeral Home Limited | Administrative & support | 2002 |
| Castleline Holdings Limited | Financial services | 2024 |
| Castleline Properties Limited | Real estate | 2025 |
| Castoc Business Hub Ltd | Hospitality | 2025 |
| Catesby Developments Limited | Construction | 1982 |
| CCR Maintenance Limited | Administrative & support | 2006 |
| CCR Motor Co. Ltd. | Wholesale & retail | 1991 |
| CD2 Limited | Real estate | 2025 |
| CDS General Ltd | Health & social care | 2024 |
| Ceda Retail Limited | Wholesale & retail | 2007 |
| Cefnef CYF | Information & communication | 2023 |
| Celt Student Services Ltd | Education | 2008 |
| Celtech Systems Ltd | Information & communication | 2003 |
| Celtic Arms Limited | Construction | 2002 |
| Celtic Dwellings Ltd | Real estate | 2024 |
| CEM Contractors Limited | Professional & scientific | 2014 |
| Central Fish Bar (Cymru) Limited | Hospitality | 2012 |
| Centreline Construction & Development Limited | Construction | 2019 |
| Centric Security Limited | Administrative & support | 2018 |
| Cenvue Ltd | Wholesale & retail | 2024 |
| Ceyloncap Limited | Wholesale & retail | 2024 |
| CF Flooring (South Wales) Ltd | Administrative & support | 2016 |
| CF24 JIU Jitsu Limited | Arts & recreation | 2016 |