| Chris Cars Sales Ltd | Wholesale & retail | 2023 |
| Chris Gomes Landscapes Ltd | Administrative & support | 2025 |
| Chris Lowrie Jointing Services Ltd | Energy | 2025 |
| Chris' Accident Repairs Ltd | Wholesale & retail | 2017 |
| Christopher Thomas & Co Limited | Real estate | 2005 |
| Christowe Ltd | Administrative & support | 2025 |
| Chumakan Limited | Other services | 2025 |
| Churchill Court Management (Harrow) Ltd | Households | 2002 |
| Churleswood Court Management Company Limited | Households | 2008 |
| Ciel Aesthetics Limited | Other services | 2025 |
| CIS Management Limited | Real estate | 2004 |
| Citrine Pharma Limited | Wholesale & retail | 2024 |
| City Escape Homes Ltd | Real estate | 2025 |
| Civic Constructions & Developments Ltd | Construction | 2005 |
| CJC Energy Tech Limited | Professional & scientific | 2020 |
| Cjlogs Limited | Administrative & support | 2018 |
| CJW Props Limited | Administrative & support | 2024 |
| CK 1699 Ltd | Professional & scientific | 2020 |
| Cladbrook Ltd | Construction | 2020 |
| Clare Management Company (1987) Limited | Households | 1987 |
| Claremont Road Ltd | Real estate | 2010 |
| Clarence Business Transformations Ltd | Professional & scientific | 2010 |
| Clarence Court Management Company Limited | Real estate | 1982 |
| Clarence Partnership Ltd | Health & social care | 2022 |
| Clarence Place Management Company Limited | Households | 2014 |
| Clarendon Court (Windsor) Management Company Limited | Households | 2000 |
| Clarendon Gate (Ottershaw) Resident Management Company Limited | Households | 1996 |
| Clarke Brothers Ltd | Construction | 2017 |
| Class 50 Alliance Heritage Ltd | Transport & logistics | 2009 |
| Class 50 Alliance Limited | Transport & logistics | 1992 |
| Class Fifty Operations Limited | Transport & logistics | 2006 |
| Class Mercedes Limited | Transport & logistics | 2023 |
| Clatterbrook Films Ltd. | Information & communication | 2017 |
| Clean Clothes Limited | Other services | 2017 |
| Clean Daffodil Ltd | Administrative & support | 2021 |
| Clean Gloucestershire Limited | Administrative & support | 2023 |
| Clean Lily of the Valley Ltd | Administrative & support | 2025 |
| Clear Hearing Windsor Ltd | Health & social care | 2024 |
| Clearpower Limited | Professional & scientific | 2007 |
| Clearsite Security Services Limited | Administrative & support | 2021 |
| Clearwater Care (Group) Limited | Health & social care | 2004 |
| Clearwater Care (Hackney) Limited | Health & social care | 2004 |
| Clearwater Specialist Care Enterprise Limited | Health & social care | 2009 |
| Clearwater Specialist Care Group Limited | Health & social care | 2009 |
| Clearwater Specialist Care Partners Limited | Health & social care | 2009 |
| Clere Suntime Company Limited(The) | Administrative & support | 1982 |
| Clever Animal Marketing Ltd | Professional & scientific | 2025 |
| Clevestyle Limited | Professional & scientific | 1984 |
| Clewer and Dedworth Together CIC | Health & social care | 2025 |
| Clewer Boatyard Limited | Manufacturing | 1943 |
| Clewer Hill Management Company Limited | Households | 1988 |
| Clinx Limited | Information & communication | 2025 |
| Cliveden Village Management Company Limited | Households | 2006 |
| Cloisters DFO Ltd | Professional & scientific | 2025 |
| Closeplace Limited | Households | 2002 |
| Clothify Wear Ltd | Wholesale & retail | 2026 |
| Clough Computer Consultants Limited | Information & communication | 1995 |
| Clover Commercial Consulting Ltd | Professional & scientific | 2024 |
| Clover Films Ltd | Information & communication | 2008 |
| Clover King Ltd | Real estate | 2026 |
| Clover Productions UK Limited | Information & communication | 2024 |
| Club One (Ascot) Limited | Hospitality | 2002 |
| Clyngwyn Limited | Hospitality | 2021 |
| CM Finance Limited | Financial services | 2021 |
| CMB Holdings NO2 Limited | Real estate | 2025 |
| CMN Property Limited | Real estate | 2023 |
| Cmnm Property Limited | Real estate | 2023 |
| Coaction Recruitment Limited | Administrative & support | 2020 |
| Coburg House (Windsor) Management Limited | Households | 2004 |
| Coco Great Property Ltd | Real estate | 2019 |
| Coco Johnston Ltd | Professional & scientific | 2026 |
| Coforge SF Limited | Information & communication | 2008 |
| Coglin Cottages Ltd | Households | 2014 |
| Cogs Accountancy Services Limited | Professional & scientific | 2014 |
| Coko Properties Ltd | Real estate | 2019 |
| Colco Coffee Ltd | Manufacturing | 2020 |
| Cole Education Recruitment Ltd | Professional & scientific | 2026 |
| Colemans Corner Ltd | Hospitality | 2025 |
| College Green Consulting Limited | Professional & scientific | 2007 |
| Collins Construct Limited | Construction | 2015 |
| Columbus United Ltd | Extraterritorial | 2023 |
| Colvin Building Consultants Limited | Professional & scientific | 1986 |
| Comer Build Interiors Limited | Construction | 2010 |
| Cometa Management Limited | Households | 2008 |
| Comfort Eating Ltd | Information & communication | 2005 |
| Commercial DNA Ltd | Extraterritorial | 2012 |
| COMMS360 Ltd | Information & communication | 2011 |
| Complete Care Windsor Limited | Health & social care | 2005 |
| Complete Conveyancing Services Limited | Information & communication | 2008 |
| Complex Claims International (Group) Ltd | Financial services | 2025 |
| Compton Taylor Limited | Administrative & support | 2006 |
| Computer Factotum Limited | Other services | 2009 |
| Computewell Limited | Information & communication | 2006 |
| Concept Living Care Services Ltd | Health & social care | 2022 |
| Concorde Energy Limited | Professional & scientific | 2013 |
| Connected Life Limited | Health & social care | 2012 |
| Conscious Clarity Ltd | Health & social care | 2022 |
| Considered Facades Limited | Construction | 2015 |
| Considered Position Ltd | Professional & scientific | 2024 |
| Constellation Aviation Consultants Limited | Professional & scientific | 2024 |