| Colag Insulations Limited | Construction | 2016 |
| Colchester Radio Ltd | Information & communication | 2018 |
| Cold Digital Limited | Professional & scientific | 2023 |
| Coleforce Limited | Construction | 2010 |
| Colin Waggon Consultants Ltd | Professional & scientific | 2023 |
| Collector Cubes Ltd | Wholesale & retail | 2024 |
| College of Business and Science UK Ltd | Administrative & support | 2022 |
| Collins Brothers Property Limited | Real estate | 2015 |
| Collins Joinery & Building Contractors Limited | Construction | 2009 |
| Collinson Contracts Limited | Manufacturing | 2007 |
| Collinson Fencing Limited | Extraterritorial | 2013 |
| Columbus One Thousand Limited | Financial services | 2019 |
| Colvill Moon Store Limited | Wholesale & retail | 2025 |
| Colville Haulage Limited | Transport & logistics | 2017 |
| Combi-Tech Ltd. | Manufacturing | 2013 |
| Come Shine With ME Billericay Ltd | Administrative & support | 2019 |
| Come Shine With ME on Sea Ltd | Administrative & support | 2020 |
| Comet Way Hatfield Limited | Construction | 2019 |
| Comfy Denture Ltd | Manufacturing | 2013 |
| Commercial Catering Equipment & Refrigeration Ltd | Manufacturing | 2024 |
| Commercial Catering Services (Catercare) Ltd | Professional & scientific | 2022 |
| Commercial Drainage Services (Essex) Ltd | Water & waste | 2017 |
| Commercial Drainage Services Limited | Water & waste | 2018 |
| Community Childcare Alliance CIC | Professional & scientific | 2023 |
| Community Healthcare Partnerships Limited | Public administration | 2021 |
| Community Solutions Point C.I.C. | Other services | 2022 |
| Comodo Workwear Ltd | Manufacturing | 2020 |
| Company Group UK Limited | Professional & scientific | 2016 |
| Compare Cosmetic Limited | Other services | 2024 |
| Compertrix Ltd | Real estate | 2021 |
| Compete Sports Group Ltd | Arts & recreation | 2023 |
| Complete Online Media Limited | Information & communication | 2008 |
| Complete Urban Solutions Limited | Extraterritorial | 2000 |
| Complete Vehicle Leasing Limited | Administrative & support | 2018 |
| Compliance & General Careers Limited | Administrative & support | 2016 |
| Compliance & General Consult Ltd | Information & communication | 2014 |
| Computus UK Limited | Information & communication | 1986 |
| Conatii UK Limited | Wholesale & retail | 2009 |
| Concat Tech Ltd | Information & communication | 2020 |
| Concept Loft Rooms Ltd | Construction | 2013 |
| Concrete Building Systems(Cbs) Limited | Construction | 2023 |
| Concrete Rendering Terrazzo Limited | Construction | 2019 |
| Connect Ceramics Limited | Health & social care | 2020 |
| Connect Floors Group Limited | Construction | 2021 |
| Connect Floors Limited | Construction | 2006 |
| Connect Logistics 365 Ltd | Administrative & support | 2019 |
| Connect Plumbing & Heating Supplies Ltd | Wholesale & retail | 2006 |
| CONNECT365GROUP Limited | Transport & logistics | 2020 |
| Connie Canty Ltd | Professional & scientific | 2023 |
| Connolly Professional Services Ltd Limited | Professional & scientific | 2018 |
| Conquer Properties Limited | Real estate | 2008 |
| Conquest Contracts Ltd | Construction | 2005 |
| Conrad Consultants Limited | Professional & scientific | 2006 |
| Consisto Ltd | Financial services | 2021 |
| Consitech Ltd | Professional & scientific | 2014 |
| Consortium Construction Ltd | Real estate | 2021 |
| Constant Development Ltd | Real estate | 2017 |
| Construct CVM Limited | Construction | 2016 |
| Constructcrest Builders Ltd | Construction | 2024 |
| Construction Consultant Services U.K Limited | Other services | 2025 |
| Construction Engineering & Management Ltd | Construction | 2023 |
| Construction Facades Limited | Construction | 2022 |
| Construction Guidance Limited | Construction | 2019 |
| Construction Robotics Systems Ltd | Manufacturing | 2025 |
| Construction Wizards Ltd | Construction | 2024 |
| Constructix Limited | Construction | 2025 |
| Consult England Limited | Professional & scientific | 2022 |
| Consulting Service for YOU Ltd | Construction | 2023 |
| Consy Healthcare Ltd | Health & social care | 2022 |
| Container Trans Ltd | Administrative & support | 2007 |
| Contavia Limited | Administrative & support | 2018 |
| Contechs Asset Management Limited | Administrative & support | 2006 |
| Contechs Consulting Limited | Information & communication | 1997 |
| Contechs Group Holdings Limited | Financial services | 2022 |
| Contechs Group Limited | Financial services | 2020 |
| Contechs Holdings Limited | Professional & scientific | 2006 |
| Contechs Materials Handling Ltd | Information & communication | 2005 |
| Contechs Technical Resourcing Ltd | Administrative & support | 2006 |
| Continental Villas Limited | Extraterritorial | 1982 |
| Contingency Planning Limited | Administrative & support | 2010 |
| Control Valve Services Ltd | Manufacturing | 2007 |
| CONVERSE7 Ltd. | Professional & scientific | 2012 |
| Conveyancing Matters Limited | Professional & scientific | 2021 |
| Coobabyboo Ltd | Manufacturing | 2018 |
| Cooksons Contracts Ltd | Construction | 2020 |
| Cooksons Electrical Services Limited | Construction | 2023 |
| Coolpanda Air Conditioning Group Ltd | Energy | 2023 |
| Coolworkwear Limited | Manufacturing | 2023 |
| Cooper Tuff Consultants Limited | Administrative & support | 2000 |
| Coopers Cleaning Services Limited | Administrative & support | 2024 |
| Coppen, Rata Limited | Professional & scientific | 1993 |
| Coppice Consulting Limited | Professional & scientific | 2022 |
| Corbu Trans Limited | Transport & logistics | 2019 |
| Cordery Construction Limited | Construction | 2002 |
| Core Engineering Services Group Ltd | Energy | 2023 |
| Core Link Recruitment Ltd | Administrative & support | 2022 |
| Corebuild Construction Ltd | Construction | 2018 |
| Corebyte Solution Limited | Information & communication | 2025 |
| Corecolumn Constructions Ltd | Construction | 2024 |
| Corecraft Dynamics Ltd | Construction | 2024 |