| Clarity Within Cognitive Behavioural Therapy Limited | Public administration | 2025 |
| Clark Smith Partnership Limited | Professional & scientific | 2000 |
| Clarke Support Company Limited | Information & communication | 1998 |
| Clarke's Carpets (Romford) Limited | Wholesale & retail | 1977 |
| Clarkes Electrical Limited | Construction | 2014 |
| Class One Driving Limited | Transport & logistics | 2007 |
| Classic Cars of Essex Ltd | Transport & logistics | 2018 |
| Classic Code Creation Ltd | Information & communication | 2024 |
| Classic Systems Limited | Information & communication | 2001 |
| Classique Deals Limited | Wholesale & retail | 2025 |
| Clau Solutions Ltd | Professional & scientific | 2024 |
| Clauruns Ltd | Transport & logistics | 2017 |
| Claya Investments Ltd | Other services | 2010 |
| Claydon Heating Group Limited | Construction | 2019 |
| Clean & Glossy Cleaning Services Ltd | Administrative & support | 2025 |
| Clean Energy & Climate Adaptation Foundation Ltd | Professional & scientific | 2026 |
| Clean Macs Ltd | Administrative & support | 2021 |
| Clean Slate Exterior Cleaning Ltd | Administrative & support | 2023 |
| Clean Tock Limited | Administrative & support | 2025 |
| Cleanco KM Limited | Administrative & support | 2008 |
| Cleaner Zone Ltd | Construction | 2024 |
| Cleaners of London Services Limited | Information & communication | 2023 |
| Cleanest Services Limited | Administrative & support | 2018 |
| Cleanfield Ltd | Construction | 2019 |
| Cleaning Bros Ltd | Other services | 2009 |
| Cleaning Tech Ltd | Administrative & support | 2026 |
| Cleansation Limited | Administrative & support | 2024 |
| Cleanxperts Limited | Administrative & support | 2025 |
| Clear Canal Clinic Ltd | Health & social care | 2025 |
| Clearance Connect Ltd | Information & communication | 2020 |
| Clearance Traders Ltd | Wholesale & retail | 2026 |
| Clearpath Compliance Ltd | Professional & scientific | 2025 |
| Clearpath Logistics Ltd | Transport & logistics | 2025 |
| Clearrend Ltd | Construction | 2025 |
| Cleartechglobal Limited | Information & communication | 2026 |
| Clearview Creative AI Limited | Information & communication | 2026 |
| Clearview Sales & Consulting Ltd | Professional & scientific | 2026 |
| Clearview Window Cleaning Services Limited | Administrative & support | 2000 |
| Clearwave Creative Ltd | Information & communication | 2026 |
| Cleaver Rowan Finishings Ltd | Construction | 2021 |
| Cleiman Records Ltd | Construction | 2025 |
| Cleo Costa Hair Studio Ltd | Other services | 2017 |
| Cleon Properties Limited | Real estate | 2023 |
| Click & Shop 1 Stop Ltd | Wholesale & retail | 2025 |
| Click and Buy U.K Ltd | Wholesale & retail | 2025 |
| Click Boom & Profit Ltd | Information & communication | 2025 |
| Click Dealz Ltd | Wholesale & retail | 2025 |
| Clickhomes Limited | Construction | 2022 |
| Clifford's Consultants Ltd | Professional & scientific | 2025 |
| Clinical Pharmsolutions Ltd | Professional & scientific | 2020 |
| Cliosport Limited | Other services | 2012 |
| Clipsham Properties Limited | Administrative & support | 1997 |
| Clive Anderson Furniture Ltd | Manufacturing | 2012 |
| Clive Hemming Productions Limited | Administrative & support | 2014 |
| Clive Morris Consulting Limited | Extraterritorial | 2014 |
| Cliveden Four Limited | Extraterritorial | 1985 |
| Clobber Ltd | Wholesale & retail | 2026 |
| Clock Removal Ltd | Construction | 2025 |
| Clock Work Recovery Ltd | Transport & logistics | 2025 |
| Clockhouse Construction Ltd | Professional & scientific | 2011 |
| Clonmore Property Investments Ltd | Professional & scientific | 2020 |
| Cloud College Ltd | Education | 2026 |
| Cloud First Marketing Agency Limited | Information & communication | 2024 |
| Cloud Kitchen Franchise Limited | Wholesale & retail | 2021 |
| Cloud Logix Ltd | Information & communication | 2013 |
| Cloud Pro Fixing Ltd | Construction | 2026 |
| Cloudbridge Software Ltd | Wholesale & retail | 2025 |
| Cloudcide Limited | Information & communication | 2022 |
| Cloudit Solutions Limited | Information & communication | 2010 |
| Cloudlink Solutions Ltd | Information & communication | 2025 |
| Cloudonic Services Ltd | Wholesale & retail | 2022 |
| Cloudstock Limited | Information & communication | 2019 |
| Cloudware Cluster Technologies Limited | Professional & scientific | 2021 |
| Cloudwave Technologies Ltd | Information & communication | 2024 |
| Cloudwey Ltd | Information & communication | 2022 |
| Cloudy People Ltd | Information & communication | 2019 |
| Clove Eastes Ltd | Real estate | 2025 |
| Clover Cottage Limited | Administrative & support | 2007 |
| Clovermead Limited | Administrative & support | 2004 |
| CLS Design Ltd | Professional & scientific | 2025 |
| Club Cricket Academy Ltd | Education | 2021 |
| Club Cricket Ltd | Wholesale & retail | 2021 |
| Club Edge Limited | Arts & recreation | 2025 |
| CM Construct Ltd | Construction | 2016 |
| CM Healthcare Construction Ltd | Construction | 2019 |
| Cm&C Design Ltd | Construction | 2017 |
| Cmarkets Limited | Information & communication | 2017 |
| CMB Security Ltd | Administrative & support | 2019 |
| CMD Transport and Recovery Ltd | Professional & scientific | 2025 |
| Cmlh Health Care Services Ltd | Health & social care | 2025 |
| CMP Consult Ltd | Professional & scientific | 2025 |
| CMS Building & Maintenance Limited | Construction | 2021 |
| CNB Solutions Ltd | Manufacturing | 2025 |
| CNG Cars Ltd | Wholesale & retail | 2020 |
| CNN Construct Ltd | Construction | 2020 |
| Cnnctin Ltd | Administrative & support | 2023 |
| CNP Install Ltd | Construction | 2021 |
| Co Investment Management Limited | Administrative & support | 2010 |
| Co Propco Limited | Real estate | 2021 |
| Coach to Teach Ltd | Professional & scientific | 2018 |