| City Airport Travels Ltd | Transport & logistics | 2024 |
| City and County Accountants Limited | Professional & scientific | 2013 |
| City Legal Consultants Limited | Professional & scientific | 2014 |
| Ciuf Ltd | Transport & logistics | 2018 |
| Ciupy Ltd | Construction | 2022 |
| Civi Holdings Ltd | Wholesale & retail | 2020 |
| CJ Retail Ltd | Wholesale & retail | 2025 |
| CJB Bookkeeping Services (Dunstable) Ltd | Professional & scientific | 2026 |
| Cjcooper Ltd | Construction | 2019 |
| CJD Services Limited | Construction | 2024 |
| Cjriggingservices Ltd | Construction | 2025 |
| Cjsb Investments Limited | Real estate | 2023 |
| CJW Projects Ltd | Construction | 2023 |
| CK Brickwork Services Limited | Construction | 2004 |
| CK Housing Ltd | Real estate | 2023 |
| Cks-Dlr Ltd | Health & social care | 2018 |
| CLA Fire Consultancy Ltd | Administrative & support | 2020 |
| CLA55 Limited | Transport & logistics | 2019 |
| Claire Penny Consulting Ltd | Professional & scientific | 2025 |
| Clare Bear Ltd | Manufacturing | 2026 |
| Claridge Interiors Limited | Construction | 2018 |
| Clark and Brown Ltd | Other services | 2023 |
| Clark Electrical Engineers Ltd | Construction | 2025 |
| Clarks Camera Centre(St.Albans)Limited | Real estate | 1971 |
| Classic Build Limited | Construction | 2013 |
| Classic Car Prizes Ltd | Wholesale & retail | 2024 |
| Classique Communitycare Services Limited | Health & social care | 2023 |
| Classirides Ltd | Transport & logistics | 2026 |
| Claud Construct Ltd | Construction | 2018 |
| Claudiu Anghel Ltd | Transport & logistics | 2025 |
| Claveyco Ltd | Information & communication | 2017 |
| Clay Kite Limited | Real estate | 2022 |
| Clayton Living Ltd | Real estate | 2019 |
| Clean Genie (Cambridge) Limited | Administrative & support | 2015 |
| Clean Team Bedfordshire Limited | Administrative & support | 2016 |
| Cleanall Supplies Ltd | Administrative & support | 2005 |
| Cleanfix Services Ltd | Administrative & support | 2026 |
| Cleaning Business Growth Academy Ltd | Extraterritorial | 2024 |
| Cleaning Innovations Ltd | Administrative & support | 2019 |
| Clearly Technical Solutions Limited | Professional & scientific | 2007 |
| Cleave Recruitment Limited | Administrative & support | 2023 |
| Clements END Farm (Studham) Management Company Limited | Households | 2022 |
| Cleopatra Cottons Limited | Wholesale & retail | 2025 |
| Click to Study Ltd | Professional & scientific | 2026 |
| Clickzy Ltd | Wholesale & retail | 2025 |
| Cliftown Limited | Hospitality | 2024 |
| Climate Action Services International LLP | | 2025 |
| Clindavis Ltd | Real estate | 2024 |
| Clinicoding Limited | Health & social care | 2026 |
| Cloud Agile Ltd | Information & communication | 2020 |
| Cloud OUT Ltd | Professional & scientific | 2015 |
| Cloudfable Ltd | Information & communication | 2026 |
| Cloudfeeder Ltd | Information & communication | 2019 |
| Cloudon IT Services Ltd | Information & communication | 2025 |
| Clouds Choice Limited | Information & communication | 2019 |
| Cloudy Cosmetics Ltd | Wholesale & retail | 2021 |
| CM Floor Screeding Limited | Construction | 2014 |
| Cm(Uk) Ltd | Hospitality | 2022 |
| CMD Facilities Ltd | Construction | 2020 |
| CMI Aylesbury Limited | Real estate | 2021 |
| CMI Beds Limited | Real estate | 2020 |
| CMI Daventree Limited | Real estate | 2021 |
| CMI Herts Limited | Real estate | 2025 |
| CMI JV Limited | Real estate | 2023 |
| CMI Luton Limited | Real estate | 2023 |
| CMI Northamptonshire Limited | Real estate | 2025 |
| CMI Wellingborough Limited | Real estate | 2022 |
| CMK Property Services Ltd | Real estate | 2017 |
| CMV Solutions Ltd | Transport & logistics | 2025 |
| CMW Compliance Solutions Limited | Professional & scientific | 2015 |
| CMW Heating Limited | Construction | 2020 |
| CNA333 Transport Ltd | Transport & logistics | 2019 |
| CNF Projects Limited | Professional & scientific | 2024 |
| Cnvv Properties Ltd | Real estate | 2025 |
| Co Tops Holdings Limited | Financial services | 2022 |
| CO2TKN Ltd | Information & communication | 2026 |
| CO5MIN Solutions Ltd | Administrative & support | 2017 |
| Coach.Jph Ltd | Other services | 2024 |
| Coakley Brickwork Ltd | Construction | 2018 |
| Coconutgrass Ltd | Arts & recreation | 2011 |
| Codevista Ltd | Professional & scientific | 2025 |
| Coffeforeveryone Ltd | Wholesale & retail | 2026 |
| Cohin-Uk Ltd | Administrative & support | 2021 |
| Coinify Limited | Real estate | 2024 |
| Cola Projects Ltd | Professional & scientific | 2021 |
| Colbeco Limited | Information & communication | 1993 |
| Cold Space Limited | Administrative & support | 2004 |
| Colemans Building Services Ltd | Construction | 2016 |
| Colin Walsh Studio Limited | Professional & scientific | 2019 |
| Collabhub Limited | Education | 2021 |
| College Farm (Chalgrave) Management Company Limited | Households | 2023 |
| Colourcourt Limited | Arts & recreation | 1997 |
| COM Church | Other services | 2017 |
| Combined Care Ltd | Health & social care | 2018 |
| Comforter Properties Ltd | Real estate | 2024 |
| Comforter Supported Services Ltd | Health & social care | 2022 |
| Comfy Spaces Development Limited | Real estate | 2023 |
| Common Road (Kensworth) Management Company Limited | Households | 2018 |
| COMMUNIC8 Wayfinding Ltd | Professional & scientific | 2026 |
| Communicate Worldwide Limited | Information & communication | 2003 |