| Circuit Moor Property Ltd | Real estate | 2025 |
| Circuit Property Limited | Real estate | 2022 |
| Circuithinking Limited | Professional & scientific | 2017 |
| Citation Cyber Limited | Information & communication | 2012 |
| Citation Fire & Electrical Limited | Extraterritorial | 2002 |
| Citation Hero Limited | Financial services | 2023 |
| Citation Holdings Limited | Information & communication | 2000 |
| Citation ISO Certification Limited | Administrative & support | 2015 |
| Citation Limited | Professional & scientific | 1995 |
| Citrus Medical Ltd | Health & social care | 2023 |
| City Island Properties Limited | Real estate | 2018 |
| City Point (Derby) Management Company Limited | Households | 2006 |
| City Project Consulting Limited | Professional & scientific | 2015 |
| CJ Analytica Ltd | Information & communication | 2024 |
| CJ Whiten Anaesthesia Limited | Health & social care | 2019 |
| Cjbm Property Ltd | Real estate | 2012 |
| CJC Walton Limited | Information & communication | 2010 |
| CJE Flooring Ltd | Construction | 2021 |
| CJG Medical Ltd | Health & social care | 2022 |
| Cjlc Ltd | Hospitality | 2019 |
| CJR Group Bristol Ltd | Water & waste | 2016 |
| Cjsi Limited | Households | 2016 |
| CJT Projects Ltd | Information & communication | 2025 |
| CK Anaesthetics Limited | Health & social care | 2021 |
| CK Property Assets Limited | Real estate | 2016 |
| Ckem Limited | Professional & scientific | 2017 |
| CKP Design Ltd | Wholesale & retail | 2024 |
| Ckpn Limited | Financial services | 2025 |
| CKS Property Group Ltd | Real estate | 2025 |
| Claith Holdings Limited | Financial services | 2025 |
| Clare Coffey Consulting Limited | Professional & scientific | 2025 |
| Clarel Investments Limited | Real estate | 2025 |
| Claremont Healthcare Ltd | Administrative & support | 2019 |
| Claremont Lodge Care Limited | Health & social care | 2008 |
| Clarity Capital Group Limited | Financial services | 2025 |
| Clarity Digital Marketing Ltd | Administrative & support | 2015 |
| Clarity EOR Limited | Administrative & support | 2025 |
| Clarity Management Information Ltd | Professional & scientific | 2018 |
| Clarity Outsourcing Group Limited | Administrative & support | 1997 |
| Clarkbeck Law Limited | Extraterritorial | 2019 |
| Clarke Cheadle Holdings Ltd | Real estate | 2025 |
| Clarke Technology Limited | Information & communication | 2019 |
| Clarutec Limited | Professional & scientific | 2023 |
| Classiq Leisure (Kampus) Limited | Real estate | 2019 |
| Classiq Leisure 5 Limited | Professional & scientific | 2022 |
| Classiq Leisure Ltd | Professional & scientific | 2009 |
| Claudia Woodhead Consulting Ltd | Professional & scientific | 2022 |
| Claxton Health Limited | Health & social care | 2023 |
| Clean Wine Limited | Manufacturing | 2020 |
| Clean Wine Retail Ltd | Wholesale & retail | 2021 |
| Clear Ahead Limited | Health & social care | 2014 |
| Clear Marketing Trustees Limited | Administrative & support | 2018 |
| Clear Psychiatry Limited | Health & social care | 2019 |
| Clear Psychology Limited | Health & social care | 2025 |
| Clear Radiology Solutions Limited | Health & social care | 2023 |
| Clear Visions (Stockport) Limited | Wholesale & retail | 2008 |
| Clemens Risk Limited | Professional & scientific | 2007 |
| Clever Beans Ltd | Information & communication | 2011 |
| Clevotec Limited | Information & communication | 2022 |
| Clicksnappy Ltd | Professional & scientific | 2025 |
| Clientsfirst Limited | Professional & scientific | 2010 |
| Clifton Road Limited | Extraterritorial | 2016 |
| Clin-E-Cal Ltd. | Professional & scientific | 2014 |
| Clinical Base Limited | Health & social care | 2024 |
| Clive Westbrook Consulting Limited | Professional & scientific | 1998 |
| CLK Studio Ltd | Information & communication | 2025 |
| Clnc Construction Limited | Construction | 2025 |
| Clocom UK Ltd | Information & communication | 2009 |
| Cloud Software Holdings Limited | Information & communication | 2017 |
| Cloud Umbrella Limited | Financial services | 2019 |
| Cloudage Ltd | Information & communication | 2022 |
| Cloudd Limited | Information & communication | 2023 |
| Cloudfish Services Ltd | Information & communication | 2021 |
| Cloverleaf Acquisitions Limited | Water & waste | 2025 |
| Cloverleaf Metals Limited | Water & waste | 2025 |
| Clustercloud.Uk Ltd | Information & communication | 2023 |
| Clwhj Properties Ltd | Real estate | 2018 |
| Clxr Limited | Arts & recreation | 2025 |
| CMS Brickwork Ltd | Construction | 2019 |
| Coalshaw Green Ltd | Transport & logistics | 2023 |
| Cobmore Holdings Ltd | Professional & scientific | 2022 |
| Codethrive Limited | Real estate | 1990 |
| Codexec Limited | Information & communication | 2017 |
| Coffee & Chit-Chat Limited | Hospitality | 2025 |
| Cogniclick Limited | Information & communication | 2017 |
| Cognition Tech Limited | Information & communication | 2024 |
| Colin Mumford Ltd | Health & social care | 2013 |
| Colin Tench Ltd | Administrative & support | 2009 |
| College Place (ST Helens) Management Company Limited | Households | 2013 |
| Colls Medical Ltd | Health & social care | 2024 |
| Colonsay Paediatrics Limited | Health & social care | 2020 |
| Colony Partners Limited | Real estate | 2015 |
| Colshaw Aircraft Ltd | Manufacturing | 2025 |
| Coltel Solutions Limited | Professional & scientific | 2025 |
| Colton Projects 2 Ltd | Real estate | 2024 |
| Colton Projects Ltd | Real estate | 2023 |
| Comet Medical Limited | Health & social care | 2023 |
| Commercial Coating Solutions Limited | Construction | 2022 |
| Commercial Retail Holdings Limited | Real estate | 2021 |
| Common Hours Ltd | Hospitality | 2025 |