| Concise Care Concepts Private Limited | Wholesale & retail | 2019 |
| Concord Asset Management Ltd | Financial services | 2012 |
| Concord Building Services Ltd | Construction | 2014 |
| Conde Consulting Limited | Professional & scientific | 2018 |
| Condomondo Ltd | Real estate | 2014 |
| Condor Solutions Ltd | Real estate | 2017 |
| Confetti & Couture Limited | Wholesale & retail | 2010 |
| Confides Consulting Limited | Professional & scientific | 2017 |
| Connect 4 Change CIC | Education | 2023 |
| Connect Drainage Limited | Construction | 2018 |
| Connect UK Electrical Contractors Ltd | Construction | 2021 |
| Connection Building Services Limited | Construction | 2017 |
| Connection Electrical & Alarm Services Limited | Construction | 2003 |
| Connective Technologies Limited | Information & communication | 2013 |
| Connectx Global Ltd | Information & communication | 2020 |
| Connolly Associates Limited | Extraterritorial | 1990 |
| Conroy Sand Ltd | Transport & logistics | 2025 |
| Cons JOB Limited | Construction | 2025 |
| Consimmons Mechatronics Ltd | Construction | 2018 |
| Consolidare Audit Limited | Professional & scientific | 2011 |
| Consolidated Storage Services Limited | Administrative & support | 2004 |
| Conson Facilities Management Consulting Limited | Administrative & support | 2025 |
| Consortium Healthcare Ltd | Health & social care | 2019 |
| Consortium Properties (Harlow) Ltd | Real estate | 2007 |
| Consortium Properties (UK) Limited | Real estate | 1997 |
| Consortium Properties PLO Ltd | Real estate | 2000 |
| Constance Amelia Limited | Administrative & support | 2025 |
| Construart Ltd | Construction | 2014 |
| Construct One Limited | Construction | 2020 |
| Construct Seer Ltd | Construction | 2025 |
| Construction B2B Ltd | Professional & scientific | 2025 |
| Construction Crafters Ltd | Construction | 2020 |
| Construction House Ltd | Construction | 2025 |
| Construction Materials Technology Ltd | Information & communication | 2024 |
| Construction Safety Consultants Ltd | Professional & scientific | 2015 |
| Construction Style Ltd | Construction | 2025 |
| Constructland Limited | Construction | 2023 |
| Consult a PM Limited | Professional & scientific | 2018 |
| Consultancy Elec Ltd | Construction | 2024 |
| Consultants' Consortium Ltd | Hospitality | 2017 |
| Consulting Direct UK Limited | Information & communication | 2003 |
| Consultingx Limited | Professional & scientific | 2024 |
| Consus Ltd | Construction | 2008 |
| Contact Construction Ltd | Construction | 2022 |
| Content Creators Ltd | Professional & scientific | 2018 |
| Content Growth Consultants Ltd | Professional & scientific | 2024 |
| Content House Media Ltd | Information & communication | 2024 |
| Continental Meat Traders Limited | Manufacturing | 2022 |
| Continental Sales Emporium Limited | Hospitality | 2003 |
| Continental Ship Services Ltd | Wholesale & retail | 2025 |
| Continuity Electrical Services Ltd | Construction | 2020 |
| Contour Privé Aesthetics Ltd | Health & social care | 2025 |
| Contour Privé Clinics Ltd | Health & social care | 2026 |
| Contract Flooring Services (London) Limited | Construction | 2005 |
| Control ALT Delete Group Limited | Information & communication | 2023 |
| Controlled Limited | Administrative & support | 1998 |
| Converge Accountants Limited | Professional & scientific | 2016 |
| Conveyance Wise Ltd | Real estate | 2024 |
| Conveyancing Quotes 4U Limited | Information & communication | 2018 |
| Conwy Multiplex Services Limited | Construction | 2020 |
| Cool & Gang Ltd. | Manufacturing | 2017 |
| Cool Rowings Ltd | Education | 2024 |
| Cool Systems Limited | Manufacturing | 2023 |
| Cool Under Fire Ltd | Arts & recreation | 2013 |
| Cooper Refurbs Ltd | Construction | 2023 |
| COP & Painters Ltd | Construction | 2019 |
| Copet Vision Ltd | Construction | 2025 |
| Copier-Fax Systems Limited | | 1984 |
| Copper Properties Ltd | Extraterritorial | 2019 |
| Coppice Yard (Block 1) RTM Company Limited | Households | 2024 |
| Coppice Yard (Block 2) RTM Company Limited | Households | 2024 |
| Coppice Yard Block Management Limited | Households | 2024 |
| Coppins Maison Ltd | Real estate | 2018 |
| Copstel Building Services Limited | Construction | 2017 |
| Coral Commerce Limited | Professional & scientific | 2019 |
| Coralex Limited | Construction | 2024 |
| Cordery Heating Services Ltd | Administrative & support | 2008 |
| Core Logic Path Ltd | Information & communication | 2025 |
| Corekonnect Ltd | Wholesale & retail | 2019 |
| Corellian Global Investments Ltd. | Information & communication | 2016 |
| Coremetrix UK Ltd | Information & communication | 2016 |
| Corenutri Ltd | Health & social care | 2025 |
| Corepath Systems Ltd | Information & communication | 2026 |
| Corepoint Construction Consultants Ltd | Wholesale & retail | 2024 |
| Coreserve Cleaning Management Ltd | Administrative & support | 2026 |
| Coresite Cleaning Ltd | Administrative & support | 2026 |
| Corevia Edge Ltd | Construction | 2018 |
| Corevital Ltd | Health & social care | 2020 |
| Corley + Woolley Limited | Construction | 2012 |
| Cornerstone Care Services Professionals Ltd | Health & social care | 2012 |
| Cornerstone Chauffeur Drive Limited | Transport & logistics | 2017 |
| Cornerstone Education Ltd | Education | 2025 |
| Cornerstone Health and Care Support Ltd | Health & social care | 2026 |
| Cornerstone Management London Limited | Construction | 2026 |
| Cornerstone Personnel NR Ltd | Construction | 2018 |
| Cornerstone Retail Group Ltd | Wholesale & retail | 2025 |
| Corporate Plus Accountancy Limited | Professional & scientific | 2009 |
| Corporate Power Limited | Energy | 2011 |
| CORPV3 Ltd | Information & communication | 2022 |
| Corr DRY Wall Limited | Construction | 2003 |