| Cornerstones Wellness Limited | Information & communication | 2026 |
| Cornish Decorators (London) Limited | Construction | 2014 |
| Cornwall Court Management Company Limited | Households | 1985 |
| Corvette Communications Limited | Information & communication | 2003 |
| Coserve Ltd. | Professional & scientific | 2016 |
| Cosmos Recruit Limited | Extraterritorial | 2011 |
| Costin Construction Ltd | Construction | 2020 |
| Cotelea Transport Ltd | Construction | 2017 |
| Cotton Grove Holdings Limited | Real estate | 2016 |
| Cotton Grove Limited | Real estate | 2014 |
| Couches Galore Ltd | Manufacturing | 2016 |
| Counselling First & Emdr Centre Ltd | Health & social care | 2026 |
| County Powder Coaters Limited | Professional & scientific | 1984 |
| Courtel Consulting Ltd | Information & communication | 2023 |
| Cousins Building Services Limited | Construction | 2016 |
| Cozy Nests Development Ltd | Real estate | 2022 |
| CPM Holdings 2024 Limited | Financial services | 2024 |
| CPO Projects Limited | Real estate | 2022 |
| Crane Support Ltd | Construction | 2016 |
| Cranfield Property Limited | Real estate | 2014 |
| Cranthorpe Millner Publishers Limited | Information & communication | 2011 |
| Craytime Limited | Hospitality | 2016 |
| CRB Direct Ltd | Administrative & support | 2019 |
| Creative Acts Limited | Education | 2006 |
| Creative Building London Ltd | Construction | 2018 |
| Creative Nuts Limited | Information & communication | 2006 |
| Creative Scapes Gardening Services Ltd | Administrative & support | 2022 |
| Creattrr Ltd | Information & communication | 2026 |
| Creek Metals Limited | Manufacturing | 1999 |
| Crescent Stables Service Company Limited | Other services | 1988 |
| Crest Contract Interiors Ltd | Wholesale & retail | 1999 |
| Cresta Estates Limited | Real estate | 1952 |
| CRF Partnership Ltd | Professional & scientific | 2015 |
| Cribb Brothers Ltd | Administrative & support | 2017 |
| Cricket Society Limited (the) | Arts & recreation | 1967 |
| Cris Construction Design and Management Ltd | Construction | 2019 |
| Croesus Consultants Limited | Professional & scientific | 2016 |
| Cromwell Lodge Management Company Limited | Households | 1996 |
| Crossfire Enterprises Ltd | Information & communication | 2005 |
| Crossfit Rayleigh Limited | Arts & recreation | 2017 |
| Crosstrak Ltd | Professional & scientific | 2020 |
| Crowdmakers Ltd | Professional & scientific | 2023 |
| Crown Capital Finance Partners Ltd. | Professional & scientific | 2023 |
| Crown Catering Cambridge Holdings Ltd | Hospitality | 2010 |
| Crown Catering Cambridge Limited | Hospitality | 2007 |
| Crown Catering Newmarket Limited | Hospitality | 2013 |
| Crown House London Limited | Real estate | 2022 |
| Crown Karat Ltd | Wholesale & retail | 2026 |
| Crown Outside Catering Limited | Hospitality | 2010 |
| Crowndee Consulting Limited | Professional & scientific | 2023 |
| Crownman Limited | Hospitality | 2013 |
| Crss Group Limited | Administrative & support | 2016 |
| Crux Commercial Advisory Ltd | Professional & scientific | 2025 |
| Crystal Communication Solutions Limited | Information & communication | 2014 |
| Crystal Holdingshk Limited | Manufacturing | 2016 |
| CS Business Training Ltd | Education | 2018 |
| CSF Aylesbury Limited | Real estate | 2022 |
| CSG Capital Limited | Administrative & support | 2025 |
| CSR Managed Services Ltd | Administrative & support | 2020 |
| Ctge Limited | Administrative & support | 2023 |
| Ctrl ALT Done Ltd | Professional & scientific | 2025 |
| CTS Translations Limited | Professional & scientific | 2022 |
| Cube Developments and Investments Limited | Construction | 2004 |
| Cube Essex LLP | | 2007 |
| Cube Hackbridge Limited | Administrative & support | 2017 |
| Cube Land Limited | Administrative & support | 2014 |
| Cube Lewisham LLP | | 2005 |
| Cube London LLP | | 2006 |
| Cube Putney Ltd | Construction | 2023 |
| Cube Retail and Leisure Limited | Administrative & support | 2025 |
| Cuffley Restaurant Limited | Hospitality | 2024 |
| Cumberland Court Woodford Green Freehold Limited | Real estate | 2014 |
| Cura Life Limited | Health & social care | 2026 |
| Curate and Co. London Ltd | Extraterritorial | 2026 |
| Curious Forms Digital Limited | Information & communication | 2025 |
| Curzon Developments Ltd | Construction | 2020 |
| Curzon Property Services Ltd | Administrative & support | 2020 |
| Customer Proposition Limited | Professional & scientific | 2017 |
| CUSTOMMADE4U Ltd | Wholesale & retail | 2026 |
| CUT Marketing Ltd | Professional & scientific | 2024 |
| Cutmore Entertainment Limited | Information & communication | 2022 |
| CX Shanghai Ltd | Hospitality | 2023 |
| Cyber Samurai Ltd | Information & communication | 2024 |
| Cyberjelly Ltd | Wholesale & retail | 2023 |
| Cynergis (UK) Limited | Wholesale & retail | 1999 |
| D & B Inc Ltd | Wholesale & retail | 2013 |
| D & a Interiors Limited | Construction | 2000 |
| D & D 80 Ltd | Construction | 2018 |
| D & I Real Estate Ltd | Real estate | 2022 |
| D C K Construction Limited | Construction | 2008 |
| D Flood Utilities Ltd | Construction | 2021 |
| D H Foods Limited | Wholesale & retail | 1999 |
| D Hatt Hairdressers Limited | Administrative & support | 2005 |
| D J K Construction Limited | Construction | 2015 |
| D J Nichols Electricals Ltd | Construction | 2020 |
| D Jewellery (HG) Ltd | Other services | 2020 |
| D Lewis Plant Hire Limited | Administrative & support | 2009 |
| D Mech Installations Ltd | Construction | 2012 |
| D P W L Stagehand Ltd | Construction | 2016 |
| D S L & Co Limited | Professional & scientific | 2013 |