| Clada Scaffolding Limited | Construction | 2013 |
| Cladek Ltd | Construction | 2024 |
| Cladini Studio Ltd | Manufacturing | 2025 |
| Clae Limited | Wholesale & retail | 2024 |
| Claimant Litigation Assistance Limited | Administrative & support | 2021 |
| Claimnotpaiddirect Limited | Professional & scientific | 2009 |
| Claire Hunt Ltd | Health & social care | 2011 |
| Clamp Limited | Information & communication | 2015 |
| Clan Automation Limited | Professional & scientific | 2020 |
| Clarence Hospitality Ltd | Hospitality | 2019 |
| Clarendon Court Flats Co.Limited | Households | 1966 |
| Claret PR Limited | Professional & scientific | 2013 |
| Clario Professional Services Limited | Professional & scientific | 2012 |
| Claris Vehicle Solutions Limited | Administrative & support | 2008 |
| Clariti Hearing Ltd | Health & social care | 2021 |
| Clarity Business Strategies Ltd | Professional & scientific | 2012 |
| Clarity Company Solutions Limited | Professional & scientific | 2009 |
| Clarity Enterprises Ltd | Real estate | 2008 |
| Clarity Glassware Ltd | Wholesale & retail | 2018 |
| Clarity Health Alliance CIC | Health & social care | 2025 |
| Clarity Health Dynamics Ltd | Health & social care | 2011 |
| Clarity Informatics Limited | Information & communication | 2000 |
| Clarity Nails & Beauty Ltd | Other services | 2018 |
| Clarity Optical Group Ltd | Wholesale & retail | 2026 |
| Clarity Personalised Solutions Ltd | Education | 2018 |
| Clarivision AI Ltd | Information & communication | 2025 |
| Clark & Partners Limited | Wholesale & retail | 1963 |
| Clark (Selby) Limited | Professional & scientific | 2004 |
| Clark Developments (Yorkshire) Ltd | Construction | 2024 |
| Clark Residential Rental Ltd | Real estate | 2024 |
| Clark Shopfitters Limited | Construction | 2011 |
| Clarke Building Services Limited | Construction | 2015 |
| Clarke Drive Properties Limited | Households | 1988 |
| Clarke Family Investments Limited | Financial services | 2019 |
| Clarke Plant Limited | Wholesale & retail | 2024 |
| Clarke-Safety Ltd | Professional & scientific | 2014 |
| Clarkegrove Limited | Real estate | 2020 |
| Clarkehouse Education Consultancy Limited | Education | 2025 |
| Class 5 Ltd | Information & communication | 2023 |
| Class a Audio Ltd | Manufacturing | 2019 |
| Class Group Limited | Wholesale & retail | 2015 |
| Class Measures Limited | Education | 2006 |
| Class Student Living Ltd | Real estate | 2016 |
| Classic Business Forms Limited | Manufacturing | 1992 |
| Classic Business Products Limited | Manufacturing | 2016 |
| Classic Detailing Limited | Administrative & support | 2025 |
| Classicar Ltd | Administrative & support | 2017 |
| Classicodes Ltd | Information & communication | 2013 |
| Classio Euro Ltd | Wholesale & retail | 2025 |
| Classique Care Services Limited | Health & social care | 2013 |
| Classique Interiors (Yorkshire) Ltd | Construction | 2002 |
| Classquest Limited | Hospitality | 1992 |
| Classy Glass Ltd | Construction | 2026 |
| Claudia.Nico Limited | Transport & logistics | 2025 |
| Claws Academy Ltd | Administrative & support | 2024 |
| Claws Consultants Ltd | Real estate | 2015 |
| Clay Architectural Designs Limited | Professional & scientific | 2018 |
| Clay Cross Coaches Ltd | Transport & logistics | 2025 |
| Clay Holdings Ltd | Financial services | 2026 |
| Clay Project Management Ltd | Professional & scientific | 2026 |
| Clayborn Construction Ltd. | Construction | 2013 |
| Clayborn Construction Worksop Ltd | Construction | 2019 |
| Clayborn Contracting Limited | Construction | 2025 |
| Claycomms Ltd | Construction | 2026 |
| Claymatic Games Ltd | Information & communication | 2019 |
| Claypenny Property Services Limited | Administrative & support | 1990 |
| Clayton & Co.(Penistone),Limited | Manufacturing | 1933 |
| Clayton Holdings & Investments Limited | Financial services | 2021 |
| Clayton Penistone Group Limited | Manufacturing | 2013 |
| Clayton Project Engineering Limited | Manufacturing | 2001 |
| Clayton Services and Property Limited | Real estate | 2025 |
| Claytons Electrical Contractors Ltd | Construction | 2024 |
| CLB Music Ltd | Arts & recreation | 2022 |
| CLB Solutions (UK) Limited | Professional & scientific | 2015 |
| CLC Digital Ltd | Information & communication | 2013 |
| CLC Grab Hire Ltd | Transport & logistics | 2025 |
| Cldwholesale Ltd | Wholesale & retail | 2025 |
| Cleag Group Ltd | Financial services | 2021 |
| Clean Club London Ltd | Health & social care | 2026 |
| Clean Getaway Carwash Ltd | Administrative & support | 2019 |
| Clean Hydration Ltd | Wholesale & retail | 2024 |
| Clean KAM Ltd | Administrative & support | 2026 |
| Clean Machine and Clearance Limited | Water & waste | 2020 |
| Clean N Clear Ltd | Administrative & support | 2020 |
| Clean Property Management Ltd | Administrative & support | 2025 |
| Clean Sweep Chimneys Limited | Administrative & support | 2025 |
| Clean Workspace Ltd | Administrative & support | 2026 |
| Clean Zone Community Network Community Interest Company | Other services | 2025 |
| CLEAN4CHANGE Ltd | Administrative & support | 2019 |
| Cleanerfix Limited | Other services | 2004 |
| Cleaning Angels Property Management & Maintenance Ltd | Administrative & support | 2016 |
| Cleaning Solutions for YOU Limited | Construction | 2017 |
| Cleaningstreak Ltd | Administrative & support | 2024 |
| Cleanline & Handyman Ltd | Professional & scientific | 2025 |
| Cleanline (South Yorkshire) Ltd | Administrative & support | 2024 |
| Cleanscape Multiglobal Limited | Wholesale & retail | 2025 |
| Cleanwise Carpet Care Limited | Administrative & support | 2014 |
| Clear BEA Consultancy Ltd | Health & social care | 2023 |
| Clear Beau Medical Ltd | Health & social care | 2023 |
| Clear Fibre Limited | Information & communication | 2020 |