| Comtegrity Systems Solutions Ltd | Information & communication | 2018 |
| Conation Data Limited | Wholesale & retail | 2006 |
| Concept (MK) Ltd | Construction | 2019 |
| Concept Clean Limited | Administrative & support | 2019 |
| Concept Companions Ltd | Administrative & support | 2026 |
| Concept Fireplaces Limited | Construction | 2025 |
| Concept Solutions (MK) Ltd | Manufacturing | 1999 |
| Conceptave Limited | Information & communication | 2021 |
| Conceptfour M&E Limited | Construction | 2022 |
| Concorde Properties Limited | Real estate | 1994 |
| Concordia Capital Investments Limited | Real estate | 2018 |
| Concrete Cars Ltd | Transport & logistics | 2017 |
| Concrete Cows Limited | Real estate | 2017 |
| CONDOR68 Ltd | Transport & logistics | 2019 |
| Conducive Developments Ltd | Real estate | 2025 |
| Confexpro Ltd | Administrative & support | 2021 |
| Conlift Ltd | Administrative & support | 2026 |
| Connaught Escapes Ltd | Real estate | 2021 |
| Connaught Security Ltd | Construction | 2010 |
| Connect and Flow Group Ltd | Wholesale & retail | 2025 |
| Connect Corporate Accommodation Ltd | Hospitality | 2024 |
| Connect Medical Solutions Limited | Administrative & support | 2021 |
| Connect Public Affairs Limited | Professional & scientific | 1997 |
| CONNECT2TALENT Limited | Administrative & support | 2011 |
| Connected CX Ltd | Professional & scientific | 2023 |
| Connectedness Limited | Professional & scientific | 2005 |
| Connection Hub Canada Ltd. | Information & communication | 2026 |
| Connectrans Logistics Limited | Transport & logistics | 2021 |
| Connex Systems Limited | Real estate | 2012 |
| Connex Telecoms Consulting Ltd | Information & communication | 2023 |
| Conniburrow Community Fridge Community Interest Company | Hospitality | 2025 |
| Connolly Accountants & Business Advisors Ltd | Professional & scientific | 1999 |
| Connolly Electrical Holdings Limited | Financial services | 2025 |
| Connolly Electrical Limited | Construction | 2010 |
| Connolly Probate Limited | Administrative & support | 2020 |
| Connolly Wills Limited | Administrative & support | 2023 |
| Conquer Tutoring Ltd | Education | 2023 |
| Conquerers Solution Ltd | Professional & scientific | 2017 |
| Consab Cleaning Services Ltd | Administrative & support | 2025 |
| Conscient Intelligence Ltd | Information & communication | 2025 |
| Conscious Choice Consulting Limited | Professional & scientific | 2018 |
| Conseb Services Limited | Education | 2014 |
| Consejo FS Ltd | Financial services | 2021 |
| Conserium Ltd | Wholesale & retail | 2022 |
| Conserva-Glaze Home Improvements Ltd | Construction | 2019 |
| Conseti UK Ltd | Professional & scientific | 2025 |
| Consilia Connect Ltd | Transport & logistics | 2024 |
| Consilia Global Ltd | Professional & scientific | 2018 |
| Consilium Design Limited | Information & communication | 2006 |
| Consilo Ltd | Professional & scientific | 2025 |
| Consistent Unit Trust Management Company Limited | Financial services | 1987 |
| Consium Limited | Information & communication | 2010 |
| Constable Construction Limited | Construction | 2003 |
| Constantin Prints Ltd | Manufacturing | 2021 |
| Constantine & Co Ltd | Professional & scientific | 2011 |
| Constantinovlad Ltd | Construction | 2022 |
| Constellation Technology Services Ltd | Information & communication | 2021 |
| CONSTRUCT4LYFE Ltd | Wholesale & retail | 2017 |
| Construction CPD Limited | Information & communication | 2019 |
| Construction Maintenance Repairs Limited | Construction | 2025 |
| Construction Management Training Ltd | Education | 2011 |
| Construction MK Ltd | Construction | 2019 |
| Construction South East Ltd | Construction | 2012 |
| CONSTRUCTION-C1 Ltd | Construction | 2025 |
| Constructive Communications Limited | Professional & scientific | 2010 |
| Constructive Resources Holdings Limited | Administrative & support | 2024 |
| Constructive Resources Limited | Administrative & support | 2002 |
| Consultancy Services of Technology Ltd. | Information & communication | 2010 |
| Consultant Cosmetic Centre Limited | Health & social care | 2014 |
| Consultant Swag Ltd | Wholesale & retail | 2020 |
| Consultavia Limited | Professional & scientific | 1995 |
| Consultdsai Ltd | Information & communication | 2020 |
| Consulting & Training Partnership Limited | Professional & scientific | 2016 |
| Consulting-Connect Ltd | Professional & scientific | 2024 |
| Consultz Global Ltd | Information & communication | 2025 |
| Consumer Dispute Resolution Limited | Households | 2014 |
| Consumer Law Limited | Professional & scientific | 2012 |
| Contact Clothing Ltd | Manufacturing | 2026 |
| Contact Studios Ltd | Wholesale & retail | 2026 |
| Contemporary Interiors Ltd | Construction | 2019 |
| Content DEV Limited | Professional & scientific | 2014 |
| Content Exchange Limited | Information & communication | 2002 |
| Contentcopilot Ltd | Wholesale & retail | 2025 |
| Contente (UK) Ltd | Wholesale & retail | 2021 |
| Contentisking Limited | Professional & scientific | 2000 |
| Contestor Legal Ltd | Other services | 2019 |
| Context Services Ltd | Construction | 2025 |
| Contingo Ltd | Professional & scientific | 2025 |
| Continio Ltd | Information & communication | 2022 |
| Continual Improvement Ltd | Professional & scientific | 2018 |
| Continuflow Ltd | Other services | 2024 |
| Contour Beauty Ltd | Other services | 2024 |
| Contract and Expand Limited | Information & communication | 2015 |
| Contract Procurement Solutions Ltd | Professional & scientific | 2010 |
| Contractiv Global Resourcing Ltd | Administrative & support | 2025 |
| Contraeez IT Limited | Administrative & support | 2016 |
| Control Print Solutions Ltd | Manufacturing | 2013 |
| Conuma Coal Limited | Extraterritorial | 2019 |
| Convergence College | Information & communication | 2019 |
| Conversationware Ltd | Administrative & support | 2007 |