| Carry on at Your Convenience C.I.C. | Other services | 2024 |
| Cartasia Ltd | Real estate | 2011 |
| Carter BED Company Ltd | Wholesale & retail | 2011 |
| Cartrefi Cwtch Ltd | Health & social care | 2021 |
| Caswell Family Property Ltd | Real estate | 2025 |
| Catalina Diamond Ltd | Hospitality | 2022 |
| Catering & Bar Installations Ltd | Construction | 2010 |
| CB Brickwork & Building Ltd | Construction | 2026 |
| CB Drainage Ltd | Water & waste | 2026 |
| Cedar Technical Services (C.T.S) Ltd | Construction | 2025 |
| Cefn Fforest Rising Stars Childcare Ltd | Health & social care | 2019 |
| Cetro Transport Service Ltd | Transport & logistics | 2025 |
| CH Carpentry and Building Ltd | Manufacturing | 2022 |
| CH DW Property Ltd | Real estate | 2026 |
| Chans Fish Limited | Hospitality | 2024 |
| Chans Kitchen UK Ltd | Hospitality | 2014 |
| Chan’S Foods Ltd | Hospitality | 2026 |
| Chargtech Ltd | Construction | 2023 |
| Chartist Developments Ltd | Professional & scientific | 2024 |
| Chastons Holdings Limited | Real estate | 2025 |
| Chastons Motor Company Limited | Wholesale & retail | 2022 |
| Cheshmedzhi Food Ltd | Hospitality | 2023 |
| Chippy 501 Limited | Hospitality | 2024 |
| Choice Domiciliary Support Agency Limited | Health & social care | 2011 |
| Chong Dynamics Limited | Hospitality | 2025 |
| Chris the Spark Ltd | Construction | 2024 |
| Ciipv Ltd | Professional & scientific | 2026 |
| City Carpets (Newport) Limited | Wholesale & retail | 2012 |
| CKP Property Developments Limited | Extraterritorial | 2012 |
| CLA Rail Ltd | Construction | 2019 |
| Clarity Independent Ltd | Health & social care | 2025 |
| Clarivo Health Ltd | Information & communication | 2025 |
| Claro Hookeye Limited | Manufacturing | 1942 |
| Claro Hookeye Services Limited | Manufacturing | 1972 |
| Classic Canines Dog Grooming Ltd | Other services | 2021 |
| CLC Training Services Ltd | Other services | 2026 |
| Clean Start (Glamorgan) Limited | Administrative & support | 2010 |
| Clean'D Ltd | Administrative & support | 2020 |
| Cleartech Cleaning Services Ltd | Administrative & support | 2025 |
| Cled Williams Coaches Limited | Information & communication | 2000 |
| Clinical Start UP Solutions Limited | Professional & scientific | 2008 |
| Clive's Bakery Limited | Manufacturing | 2003 |
| Clock Tower Estates Limited | Construction | 2005 |
| Coachedbychaney Ltd | Arts & recreation | 2024 |
| Coco Promotions Limited | Administrative & support | 2025 |
| Collaboration INK Ltd | Other services | 2017 |
| Communite Ltd | Information & communication | 2008 |
| Community Active Travel Services Ltd | Transport & logistics | 2021 |
| Complete Solutions Construction Ltd | Construction | 2026 |
| Content Makers Ltd | Information & communication | 2016 |
| Cooling Intelligence Ltd | Professional & scientific | 2026 |
| Coote Financial Planning Ltd | Professional & scientific | 2025 |
| Cornerstone Retail Services Ltd | Other services | 2017 |
| Correct IT and Protect IT Limited | Wholesale & retail | 2018 |
| COSYHOMES2211 Ltd | Construction | 2025 |
| Cosywarmth Windows Limited | Construction | 2023 |
| Country Fields Limited | Other services | 2010 |
| Covenant Consulting Ltd | Professional & scientific | 2025 |
| CP Plastering Services Ltd | Construction | 2020 |
| CR7 Homes Ltd | Real estate | 2024 |
| Craig Project Management Limited | Professional & scientific | 2023 |
| Crosshands Care Limited | Health & social care | 2010 |
| Crosskeys Automotive Ltd | Wholesale & retail | 2024 |
| CRS. Assist & Repairs Ltd | Manufacturing | 2025 |
| Crs.Assist&Repair Services Ltd | Wholesale & retail | 2025 |
| Crystal HCW Ltd | Other services | 2025 |
| CSC Blackwood Ltd | Hospitality | 2025 |
| CSH Contracting Services Limited | Construction | 2026 |
| CT Financial Services Ltd | Financial services | 2026 |
| CT Global Group Ltd | Financial services | 2022 |
| Cupcake Heaven Ltd | Other services | 2016 |
| Curious Pursuits Ltd | Education | 2022 |
| Curley Property Ltd | Construction | 2024 |
| Custom Carpentry Solutions Ltd | Construction | 2025 |
| Cwtch Lettings Limited | Real estate | 2026 |
| CŴL Tech CYF. | Construction | 2025 |
| D & C Carpentry Ltd | Manufacturing | 2025 |
| D & D Substructures Limited | Construction | 2024 |
| D & L Physiotherapy Ltd | Health & social care | 2019 |
| D & M Groundworks & Utilities Ltd | Construction | 2017 |
| D Davies Groundworks Ltd | Construction | 2023 |
| D Ware Transport Ltd | Transport & logistics | 2021 |
| D&L Civils & Plant Hire Ltd | Administrative & support | 2025 |
| D&M Plant Hire & Utilities Limited | Construction | 2020 |
| D.H.S. Construction Services Ltd | Construction | 2017 |
| D.N.A Security Services Ltd | Financial services | 2021 |
| DAK Brickwork Ltd | Construction | 2026 |
| Dakn Property Ltd | Real estate | 2025 |
| Dale Rees Services Limited | Manufacturing | 2002 |
| Daniel Price Carpentry Limited | Construction | 2018 |
| Dark & Hillman Construction Ltd | Construction | 2003 |
| Darren Lewis Transport Limited | Construction | 2013 |
| Davies Plastering and Properties Limited | Construction | 2021 |
| Davies Scaffolding Ltd | Construction | 2025 |
| Delish (Catering) Ltd | Hospitality | 2018 |
| Derek Smith Roughcasters Limited | Construction | 2008 |
| DET4ILED Ltd | Administrative & support | 2024 |
| DEV Studios Limited | Information & communication | 2025 |
| Diamond Racing Limited | Arts & recreation | 1994 |
| Dirt Wheelz UK Limited | Wholesale & retail | 2023 |