| Clear Project & Portfolio Management Limited | Information & communication | 2022 |
| Clear Thought Marketing Consultancy Limited | Professional & scientific | 2020 |
| Clear Wash Window Cleaning Ltd | Administrative & support | 2025 |
| Clearagent Limited | Other services | 1995 |
| Clearance Appliances Outlet Limited | Wholesale & retail | 2026 |
| Clearbridge Technologies Ltd | Information & communication | 2026 |
| Clearcycle Ltd | Wholesale & retail | 2015 |
| Clearflow Engineering & Management Ltd | Administrative & support | 2024 |
| Clearoutcome Limited | Professional & scientific | 2005 |
| Clearscope Surveying Ltd | Administrative & support | 2025 |
| Cleartech Consultancy Limited | Information & communication | 2021 |
| Clem Davies Hygiene Ltd | Hospitality | 2025 |
| Clevaevent Planning Ltd | Administrative & support | 2024 |
| Clevaops Planning Ltd | Administrative & support | 2024 |
| Cleveland Metals Limited | Extraterritorial | 1959 |
| Cleveland Scott Investments Limited | Financial services | 2023 |
| Cleveland Scott Limited | Professional & scientific | 2017 |
| Clever Disk Shop Ltd | Wholesale & retail | 2014 |
| Click 'N' Order Limited | Information & communication | 2010 |
| Click ME Ltd | Wholesale & retail | 2024 |
| Click Trading Limited | Wholesale & retail | 2006 |
| Client Bridge Adult Residential Ltd | Health & social care | 2017 |
| Client Bridge Child Resi Solutions Ltd | Public administration | 2017 |
| Client Bridge Domicilliary Solutions Ltd | Public administration | 2017 |
| Client Bridge Group Ltd | Information & communication | 2015 |
| Client Bridge Holdings Limited | Financial services | 2017 |
| Client Bridge Leaving Care Ltd | Health & social care | 2017 |
| Client Bridge Management Ltd | Professional & scientific | 2021 |
| Client Connect Ltd | Professional & scientific | 2024 |
| CLIENT1ST Software Ltd | Information & communication | 2011 |
| Cliff Box Ltd | Real estate | 2024 |
| Clifford Network Solutions Limited | Administrative & support | 2015 |
| Clifton Building Services Limited | Construction | 2003 |
| Clifton Instrumentation Ltd | Other services | 2002 |
| Clinica Cosmetics Ltd | Other services | 2024 |
| Clinix Technology Limited | Information & communication | 2017 |
| Clinpharma Ltd | Administrative & support | 2014 |
| Clive Bowyer Accountants Limited | Professional & scientific | 2025 |
| Clive Bowyer Limited | Professional & scientific | 2025 |
| Cllas Consulting Ltd | Professional & scientific | 2015 |
| CLM Clinical Research Ltd | Administrative & support | 2023 |
| CLN London Ltd | Other services | 2019 |
| Clock Face Carpets Ltd | Wholesale & retail | 2008 |
| Clockface Holdings Limited | Professional & scientific | 2022 |
| Cloco Clinic Ltd | Other services | 2024 |
| Cloco Hairdressing Limited | Other services | 2025 |
| Cloco Limited | Other services | 2023 |
| Clonwhelan Limited | Administrative & support | 2022 |
| Close Parent Limited | Manufacturing | 2004 |
| Close the Loop Consulting Limited | Professional & scientific | 2023 |
| Cloud 10 Accounting Group Limited | Financial services | 2024 |
| Cloud 10 Accounting Holdings Limited | Financial services | 2026 |
| Cloud 10 Accounting Limited | Professional & scientific | 2021 |
| Cloud Corporate Limited | Information & communication | 2008 |
| Cloud IT Consultancy Ltd | Information & communication | 2019 |
| Cloud Ledger Solutions Ltd | Professional & scientific | 2024 |
| Cloud Native Software Ltd | Extraterritorial | 2021 |
| Cloud Nine Resource Ltd | Administrative & support | 2024 |
| Cloud Objectives Limited | Information & communication | 2016 |
| CLOUD4 Technology Ltd | Information & communication | 2009 |
| CLOUD9 Defence Limited | Administrative & support | 2014 |
| CLOUD9 IT Consultancy Ltd | Information & communication | 2019 |
| Cloudence Limited | Information & communication | 2025 |
| Cloudha Ltd | Information & communication | 2024 |
| Cloudjump Ltd | Information & communication | 2018 |
| Cloudlift Limited | Professional & scientific | 2022 |
| Cloudplex Ltd | Information & communication | 2020 |
| Clouds Wings Food Ltd | Wholesale & retail | 2024 |
| Cloudswing Limited | Administrative & support | 2015 |
| Cloudwissen Ltd | Professional & scientific | 2019 |
| Cloudzzy Ltd | Information & communication | 2019 |
| Clough & Barton Property Ltd | Real estate | 2026 |
| Clovelly Properties Limited | Real estate | 2023 |
| Cloverleaf Media Limited | Information & communication | 2003 |
| Clubhouse Golf Limited | Wholesale & retail | 2003 |
| Clue HQ Ltd | Arts & recreation | 2014 |
| Clump Farm Solar Limited | Construction | 2019 |
| CLW Accounting Solutions Ltd | Professional & scientific | 2016 |
| CLW Building Maintenance Ltd | Water & waste | 2023 |
| CLW Communications Ltd | Professional & scientific | 2025 |
| CM Design Solutions Limited | Administrative & support | 2014 |
| CM Plastering Ltd | Administrative & support | 2025 |
| CM Property Rentals Ltd | Real estate | 2020 |
| CM Syndicate Ltd | Manufacturing | 2020 |
| Cm&C Investment Limited | Real estate | 2023 |
| CMB Renovations Ltd | Construction | 2023 |
| CMC Energy Consultants Limited | Administrative & support | 2015 |
| CMF Projects Limited | Administrative & support | 2023 |
| CMG Tunnelling Limited | Construction | 2023 |
| CMK Software Limited | Information & communication | 2017 |
| Cmnova Ltd | Professional & scientific | 2025 |
| CMQ Solutions Limited | Information & communication | 2015 |
| CMR Jobs Limited | Administrative & support | 2023 |
| CMS Computers Limited | Manufacturing | 1996 |
| CMS Fork Trucks Ltd | Administrative & support | 2011 |
| CMS Network (London) Ltd | Transport & logistics | 1998 |
| CMT Services Limited | Administrative & support | 2013 |
| Cmty Ltd | Financial services | 2022 |
| Cmuk Holdings Limited | Financial services | 2025 |
| CMV Transporter Ltd | Transport & logistics | 2025 |