| Clark Woodward Hungate & Co Limited | Professional & scientific | 2023 |
| Clarke & Carter (Holdings) Limited | Financial services | 2016 |
| Clarke & Carter Interyacht Limited | Wholesale & retail | 1984 |
| Clarke & Clarke Properties Limited | Real estate | 2016 |
| Clarke Cole Accounting Limited | Professional & scientific | 2013 |
| Clarke Construction (Ipswich) Limited | Construction | 2014 |
| Clarke Development Group Ltd | Real estate | 2025 |
| Clarke Real Estate Ltd | Real estate | 2021 |
| Clarke Renovations Limited | Administrative & support | 2017 |
| Clarkes 24/7 Ltd | Construction | 2014 |
| Clarkson Property Ltd | Real estate | 2019 |
| Clarosoft Solutions Limited | Information & communication | 2017 |
| Classic Yacht Charter Limited | Transport & logistics | 2005 |
| Claudiu Spedition Ltd | Transport & logistics | 2023 |
| Clauss Trans Ltd | Transport & logistics | 2015 |
| Claydon & Barham Local Community Trust Limited | Other services | 2002 |
| Claydon Court Ltd | Real estate | 1992 |
| Claydon Executive Coaches Ltd | Transport & logistics | 2019 |
| Claydon Executive Travel Ltd | Transport & logistics | 2016 |
| Claydon Mortgage Services Limited | Financial services | 2014 |
| Claydon Precision Machining Limited | Manufacturing | 1988 |
| Claydon Skip Hire Ltd | Water & waste | 2006 |
| Claydon Tiling Ltd | Construction | 2010 |
| Claydon Travel Ltd | Transport & logistics | 2020 |
| Clayton Alexander Ltd | Construction | 2023 |
| Clean and Decoratively Ltd | Administrative & support | 2023 |
| Clean Co Prestige Ltd | Administrative & support | 2025 |
| Clean IT Window Cleaning Ltd | Administrative & support | 2021 |
| Clean IT With Holly Ltd | Administrative & support | 2023 |
| Clean Pristine Cleaning Limited | Administrative & support | 2025 |
| Clean Shoes Limited | Professional & scientific | 2000 |
| Clean Show Productions Ltd | Information & communication | 2025 |
| Clean Tech Ltd | Wholesale & retail | 2026 |
| Clean World VBC Ltd | Administrative & support | 2022 |
| Cleandata Systems Limited | Information & communication | 1996 |
| Cleanest Windows Limited | Administrative & support | 2009 |
| Cleanhse Services Ltd | Construction | 2017 |
| Cleaning Beny Ltd | Construction | 2024 |
| Cleaning I Limited | Administrative & support | 2025 |
| Cleaning Services D&A Ltd | Administrative & support | 2022 |
| Cleanse Crew Ltd | Administrative & support | 2026 |
| Cleanup Maintenance Services LLP | | 2007 |
| Clear 7 Consultancy Limited | Information & communication | 2017 |
| Clear Choice Hand Car Wash Ltd | Other services | 2024 |
| Clear Idea Finance Limited | Financial services | 2020 |
| Clear Management Solutions Limited | Real estate | 2001 |
| Clear MUD Media Ltd | Professional & scientific | 2019 |
| Clear Recovery Limited | Other services | 2013 |
| Clearfield Recruitment Ltd | Administrative & support | 2010 |
| Clearframe LLP | | 2026 |
| Clearly Care Ltd | Administrative & support | 2023 |
| Clearly Properties Ltd | Real estate | 2023 |
| Clearscore Limited | Manufacturing | 1978 |
| Clearsound Consulting Limited | Professional & scientific | 2026 |
| Clearsound Hearing Limited | Health & social care | 2012 |
| Clearvoice Nigeria Limited | Other services | 2025 |
| Clements Solicitors Limited | Administrative & support | 2013 |
| Clen WAE Agriculture Ltd | Agriculture & fishing | 2025 |
| Clever Property People Ltd | Real estate | 2026 |
| Clever Property Stays Ltd | Hospitality | 2026 |
| Clever Shield Ltd | Construction | 2021 |
| Click Retail Ltd | Wholesale & retail | 2016 |
| CLICK2GLAZE Limited | Wholesale & retail | 2025 |
| Clickhive Studios Ltd | Professional & scientific | 2025 |
| Cliff Lane Flooring Limited | Wholesale & retail | 2019 |
| Clifford Agharese Ltd | Health & social care | 2019 |
| Clima-Tech Hvac Ltd | Energy | 2019 |
| Clinic Brands Ltd | Wholesale & retail | 2023 |
| Clinical Computing UK Limited | Information & communication | 1995 |
| Clinician.Pa Ltd | Health & social care | 2021 |
| CLN Haulage Ltd | Transport & logistics | 2020 |
| Clocat Limited | Construction | 2016 |
| Clopton Investments Limited | Administrative & support | 2023 |
| CLOTH2COIN LLP | | 2025 |
| Cloud Counting Ltd | Professional & scientific | 2021 |
| Cloud Techees Ltd | Information & communication | 2023 |
| Cloudcraftr LLP | | 2024 |
| Cloudflex Systems Ltd | Information & communication | 2013 |
| Cloudshift Consulting Ltd | Information & communication | 2025 |
| Cloudshop Limited | Information & communication | 2019 |
| Clouting Products Ltd | Wholesale & retail | 2024 |
| Clover Properties East Anglia Limited | Real estate | 2022 |
| Cloverd Trade Limited | Wholesale & retail | 2026 |
| Clowbridge Properties Ltd | Real estate | 2024 |
| CLP Solutions Limited | Information & communication | 1998 |
| Cluck'D Holdings Ltd | Hospitality | 2023 |
| Cluck'D Masters Ltd | Hospitality | 2024 |
| Clueflow Ltd | Professional & scientific | 2023 |
| Cluetopia Ltd | Arts & recreation | 2022 |
| CLW Properties Limited | Construction | 2013 |
| CMA Garden Solution Ltd | Construction | 2017 |
| CMA Tint and Shine Ltd | Manufacturing | 2024 |
| CME GRP Limited | Information & communication | 2026 |
| Cmex Group Ltd | Administrative & support | 2025 |
| CMI Foiling Ltd | Manufacturing | 2023 |
| CMK Transport Ltd | Transport & logistics | 2014 |
| Cmlpropertyservices Limited | Real estate | 2023 |
| CMR Garage Limited | Wholesale & retail | 2016 |
| CMS Logistics Management Ltd | Transport & logistics | 2005 |
| CNA Care Services Ltd | Health & social care | 2020 |