| Cine Lighting Limited | Information & communication | 2015 |
| Citadel Design & Build Ltd | Professional & scientific | 2019 |
| City & Commercial Property Company Limited | Real estate | 1980 |
| City Capital Consulting Ltd | Administrative & support | 2006 |
| Ckip Ltd | Hospitality | 2021 |
| Clair Hall Ltd | Professional & scientific | 2017 |
| Claire Hogg Mortgages & Protection Limited | Financial services | 2019 |
| Clapamo Limited | Professional & scientific | 2025 |
| Clapham Road Properties Ltd | Real estate | 2023 |
| Clara Learning Ltd | Information & communication | 2026 |
| Clarendon Court (KEW) Management Company Limited | Households | 1967 |
| Clarity SMC Limited Liability Partnership | | 2006 |
| Clark Traffic Ltd | Construction | 2023 |
| Clarke Waller Limited | Professional & scientific | 2002 |
| Classic Experiences (Pitlochry) Limited | Real estate | 2005 |
| Classic Experiences Limited | Construction | 2004 |
| Classic Properties ( Southport ) Ltd | Extraterritorial | 2023 |
| Cleanbooks Ltd | Professional & scientific | 2018 |
| Clear Choice Services Ltd | Transport & logistics | 2025 |
| Clear EAR Surrey Ltd | Health & social care | 2024 |
| Clear Partners Limited | Administrative & support | 2004 |
| Clearafix Ltd | Health & social care | 2017 |
| Clearafix Solutions Ltd | Information & communication | 2018 |
| Clearpath Labs Ltd | Information & communication | 2026 |
| Clearthought Solutions Limited | Professional & scientific | 2006 |
| Clearwood Holdings Ltd | Financial services | 2024 |
| Cleeve Lodge Care Limited | Health & social care | 2006 |
| Clennell Plant Repairs Limited | Manufacturing | 2007 |
| Cleskan Ltd | Professional & scientific | 2026 |
| Cleveland Court (KEW) Tenants Association Limited | Households | 1961 |
| Cleveland Readymix Limited | Manufacturing | 2019 |
| Clhm Limited | Real estate | 2016 |
| Clipgate Limited | Professional & scientific | 2005 |
| Clipstone Cottages Ltd | Real estate | 2023 |
| Cloud Apartments Limited | Wholesale & retail | 2015 |
| Cloud Nine Real Estate Limited | Real estate | 2019 |
| Cloud Officer Limited | Information & communication | 2016 |
| Cloud Resourcing Ltd | Administrative & support | 2024 |
| CLOUD9 Software Limited | Information & communication | 2015 |
| Cloverfield Services Limited | Administrative & support | 2021 |
| CLP TM Limited | Construction | 2026 |
| Club Avandra Limited | Professional & scientific | 2025 |
| CN2UK Ltd | Manufacturing | 2013 |
| Cnc-It Limited | Manufacturing | 2000 |
| CNS Engineering Ltd | Professional & scientific | 2024 |
| CO13RA Exterior Cleaning Services Ltd | Administrative & support | 2025 |
| COA Network Ltd | Information & communication | 2021 |
| Coates Westfield LLP | | 2023 |
| Cobden Park Limited | | 2010 |
| Cobraflow Limited | Information & communication | 2000 |
| Cocoa Plantations Limited | Real estate | 2016 |
| Coddiwomple Tours Limited | Administrative & support | 2016 |
| Codern Technology UK Ltd | Information & communication | 2025 |
| Coffee and Cake Co Limited | Hospitality | 2015 |
| Cogenesis Ltd | Financial services | 2002 |
| Coggrave Holdings Limited | Financial services | 2026 |
| Cogital Limited | Construction | 2014 |
| Cole Contracting Ltd | Agriculture & fishing | 2026 |
| Colin Ferns 25 Ltd | Wholesale & retail | 2025 |
| Colin Ferns Limited | Wholesale & retail | 2008 |
| Colin Ford Bespoke Joinery Limited | Manufacturing | 2005 |
| Collins Waterage & Lighterage Limited | Administrative & support | 2008 |
| Color Automatic Limited | Arts & recreation | 2017 |
| Colour House Management Limited | Households | 2020 |
| Coltan Consulting Limited | Professional & scientific | 2013 |
| COM Agency Group Ltd | Professional & scientific | 2023 |
| Commerce AZ Ltd | Wholesale & retail | 2024 |
| Communal Aerials Limited | Information & communication | 2007 |
| Communicate With Purpose Limited | Administrative & support | 2024 |
| Community Housing and Therapy | Health & social care | 1994 |
| Community Planning Alliance Limited | Professional & scientific | 2022 |
| Compass Box Holdings Limited | Financial services | 2022 |
| Compass Box Whisky Supply Ltd | Manufacturing | 2012 |
| Compass, MAP and Key Ltd | Information & communication | 2025 |
| Competitive Thinking Ltd | Professional & scientific | 2025 |
| Complete Animal Health Limited | Agriculture & fishing | 2004 |
| Completely Crush Limited | Information & communication | 2013 |
| Comrades Live Entertainment Ltd | Hospitality | 2025 |
| Concepte Ltd | Information & communication | 2016 |
| Concierge Yacht Consignment Ltd | Transport & logistics | 2022 |
| Confirmdata Ltd | Information & communication | 2019 |
| Conifers School Holdings Limited | Financial services | 2023 |
| Conker Advisory Ltd | Financial services | 2020 |
| Conker Design Limited | Information & communication | 2000 |
| Connect Telecom UK Limited | Information & communication | 2001 |
| CONNECT2LAW Limited | Other services | 2004 |
| Connectere Technologies Limited | Information & communication | 2025 |
| Connective Capital Limited | Professional & scientific | 2024 |
| Connoisseur of Malvern Limited | Extraterritorial | 2015 |
| Conservation and Technical Services Limited | Professional & scientific | 1989 |
| Conservation Technology & Machinery Limited | Wholesale & retail | 2001 |
| Consilium AMS Limited | Professional & scientific | 2011 |
| Consolidated Automotive International Limited | Wholesale & retail | 2023 |
| Consolidated Investment and Trading Limited | Professional & scientific | 2012 |
| Constantia Computing Limited | Information & communication | 2000 |
| Constanze Interior Projects Limited | Other services | 2002 |
| CONSTRUCT365 Limited | Information & communication | 2015 |
| Construction Project Management Consultants Limited | Construction | 2000 |
| Consulting Cloud Ltd | Information & communication | 2015 |
| Consultiqa Limited | Information & communication | 2012 |