| Clare James Automotive Limited | Wholesale & retail | 2004 |
| Clare James Trade Parts LLP | | 2007 |
| Clarence House Management (Milton Keynes) Limited | Real estate | 2004 |
| Clarendon Security Ltd | Administrative & support | 2024 |
| Clares Horses Central Bedfordshire Limited | Agriculture & fishing | 2009 |
| Clarity Digital Limited | Administrative & support | 2006 |
| Clarity Flow Ltd | Administrative & support | 2026 |
| Clarity Insights (Europe) Limited | Professional & scientific | 2016 |
| Clarity Legal Services Limited | Professional & scientific | 2018 |
| Clarity of Sight Ltd | Wholesale & retail | 2010 |
| Clarity People Ltd | Professional & scientific | 2017 |
| Clarity Technology Holdings Limited | Extraterritorial | 2003 |
| Clarity Unfolding Limited | Health & social care | 2025 |
| Clariwell UK Ltd | Wholesale & retail | 2025 |
| Clark & SON Electrical Service Limited | Other services | 2001 |
| Clark Construction (ALL Aspects) Ltd | Construction | 2020 |
| Clarke-Rendall Business Furniture Limited | Manufacturing | 1992 |
| Clarkes Carpentry Limited | Manufacturing | 2016 |
| Clarkson Consultancy Limited | Professional & scientific | 2025 |
| Class 1 Driver Ltd | Transport & logistics | 2025 |
| Classic House Ltd | Wholesale & retail | 2019 |
| Classic Stockcars Ltd | Arts & recreation | 2023 |
| Classic Transport Consultancy Ltd | Transport & logistics | 2004 |
| Classical Style Designs Ltd | Manufacturing | 2024 |
| Classicmobilia Limited | Wholesale & retail | 2009 |
| Classroom Adventures Ltd | Arts & recreation | 2016 |
| Clauclem Limited | Professional & scientific | 2025 |
| Claude Bosi Investments Ltd | Financial services | 2023 |
| Claude Bosi Limited | Professional & scientific | 2018 |
| Claude Trade Ltd | Transport & logistics | 2021 |
| CLAVER01 Ltd | Health & social care | 2013 |
| Claxton Trading Limited | Real estate | 2021 |
| Clay Records Limited | Other services | 1989 |
| Claybell Limited | Financial services | 2012 |
| Claydon Equestrian Limited | Agriculture & fishing | 2026 |
| Claydon Partners Limited | Financial services | 2014 |
| Clays Developments Ltd | Real estate | 2025 |
| Clays Estates Ltd | Real estate | 2021 |
| Clays Vehicle Repairs Limited | Wholesale & retail | 2013 |
| Clayton's of Mansfield Limited | Wholesale & retail | 2008 |
| CLB Restaurant Limited | Hospitality | 2025 |
| CLCH25 Limited | Households | 2025 |
| Cldperformance Limited | Health & social care | 2023 |
| CLE Consulting Limited | Information & communication | 2015 |
| Clean & Sparklie Ltd | Administrative & support | 2024 |
| Clean 24 Seven Ltd | Administrative & support | 2024 |
| Clean 32 Ltd | Administrative & support | 2021 |
| Clean and Tidy Services Ltd | Administrative & support | 2025 |
| Clean Bright Limited | Administrative & support | 2025 |
| Clean Environment Services Limited | Administrative & support | 2012 |
| Clean Tech Events Ltd | Administrative & support | 2022 |
| Cleandeer Ltd | Administrative & support | 2015 |
| Cleanedbymilla Ltd | Administrative & support | 2024 |
| Cleaner Bins MK Limited | Administrative & support | 2009 |
| Cleaner Bins NN Ltd | Administrative & support | 2017 |
| Cleaner MK Limited | Administrative & support | 2021 |
| Cleaner Windows MK Ltd | Administrative & support | 2024 |
| Cleaning Care Limited | Other services | 2006 |
| Cleaning Holdings Limited | Administrative & support | 2018 |
| Cleaning Lovers MK Ltd | Administrative & support | 2026 |
| Cleaning Tools Limited | Wholesale & retail | 2016 |
| Cleanpro Facilities Management Ltd | Administrative & support | 2024 |
| Cleanslate F.C. C.I.C. | Arts & recreation | 2013 |
| Clear Aperture Media Ltd | Information & communication | 2021 |
| Clear Complexions Ltd | Other services | 2023 |
| Clear Horizon Energy Ltd | Professional & scientific | 2023 |
| Clear Mode Studio Ltd | Information & communication | 2026 |
| Clear Project Direction Limited | Professional & scientific | 2010 |
| Clear Property Direction Limited | Real estate | 2016 |
| Clear Sight Windows & Doors Limited | Construction | 2023 |
| Clear Sites Consultancy Ltd | Professional & scientific | 2014 |
| Clearbus Enterprises Limited | Real estate | 2020 |
| Clearer Clinics Ltd | Health & social care | 2019 |
| Clearer Training Limited | Education | 2024 |
| Clearfume U.K. Limited | Manufacturing | 2007 |
| Clearly Secure Limited | Construction | 1995 |
| Clearminds Education Limited | Education | 2015 |
| Clearpath Solutions Consulting Ltd | Professional & scientific | 2026 |
| Clearpath Solutions Ltd | Transport & logistics | 2024 |
| Clearsettle Limited | Transport & logistics | 2025 |
| Clearsight Visioncare Limited | Wholesale & retail | 2018 |
| Clearsights Limited | Real estate | 2008 |
| Clearskye Ventures Ltd. | Hospitality | 2013 |
| Clearsolve Ltd | Water & waste | 2025 |
| Cleartrace Consultants Ltd | Professional & scientific | 2025 |
| Clearview Drainage Ltd | Water & waste | 2025 |
| Clearview Intelligence Group Limited | Manufacturing | 1995 |
| Clearview Intelligence Limited | Manufacturing | 1987 |
| Clearview Pressure Washing Ltd | Administrative & support | 2022 |
| Clearview Roofing & Glazing Limited | Construction | 2025 |
| Clearware 2000 Limited | Transport & logistics | 1998 |
| Clearwater Event People Ltd | Administrative & support | 2019 |
| Clearwater People Ltd | Administrative & support | 2009 |
| Clearwater Stud Limited | Agriculture & fishing | 2018 |
| Cleek Railway Solutions Limited | Transport & logistics | 2003 |
| Clement Developments Limited | Construction | 2021 |
| Clendon Services Limited | Education | 2018 |
| Clenz Beauty Ltd | Other services | 2023 |
| Cleo Skin Limited | Health & social care | 2024 |
| Cleonix Ltd | Administrative & support | 2026 |