| Commercial Automotive Guarantee Corporation Limited | Extraterritorial | 1987 |
| Commercially Yours Ltd | Professional & scientific | 2017 |
| Communication Design Partnership Limited | Professional & scientific | 1984 |
| Community Assessment and Therapies Services C.I.C. | Health & social care | 2011 |
| COMPANY52 Ltd | Wholesale & retail | 2019 |
| Compass Business Solutions Limited | Real estate | 2005 |
| Compass Scaffolding Ltd | Construction | 2021 |
| Complete Site Contracts Ltd | Administrative & support | 2016 |
| Composite Machining Academy Ltd | Professional & scientific | 2024 |
| Composite Wood Shop Ltd | Professional & scientific | 2020 |
| Comproom Limited | Construction | 1999 |
| Compudrip Limited | Extraterritorial | 2016 |
| CON Mech Paddocks Limited | Financial services | 2019 |
| CON Mech Suffolk Limited | Financial services | 2019 |
| Conavi Ltd | Wholesale & retail | 2023 |
| Concept Blinds & Shutters Ltd | Wholesale & retail | 2016 |
| Concept Coffee Systems Limited | Wholesale & retail | 2011 |
| Concept Group Services (UK) Ltd | Construction | 2024 |
| CONCEPT2CONSULTING Ltd | Professional & scientific | 2023 |
| Conceptgate Limited | Information & communication | 2015 |
| Concord Capital Limited | Administrative & support | 2007 |
| Concorde 25 Ltd | Transport & logistics | 2025 |
| Conditionaire International Limited | Manufacturing | 2009 |
| Confidence Driving School Limited | Education | 2024 |
| Congestless Limited | Information & communication | 2026 |
| Connect Centre Limited | Real estate | 2014 |
| Connectacard Ltd | Financial services | 2014 |
| Connectaphone Ltd | Information & communication | 1989 |
| Connors Caravan Limited | Hospitality | 2025 |
| Conquers Mediation & Strategic Solutions Limited | Administrative & support | 2011 |
| Consult Electric Limited | Construction | 2010 |
| Consult One Ltd | Information & communication | 2025 |
| Consulting 2U Limited | Professional & scientific | 2001 |
| Contender Gym Apparel Ltd | Wholesale & retail | 2026 |
| Content for Business Limited | Information & communication | 2010 |
| Contractors/Plant Hire (Reading) Ltd | Administrative & support | 1997 |
| Contrologica Limited | Education | 2014 |
| Conversifi Limited | Information & communication | 2025 |
| Convolution SUM Ltd | Financial services | 2018 |
| Conway Aecom Limited | Construction | 2012 |
| Conway Eurovia Industries Limited | Manufacturing | 2025 |
| Conway Minerals Limited | Extraterritorial | 2025 |
| Cook Structural Engineers Limited | Professional & scientific | 2021 |
| Coolings Green & Pleasant Ltd | Wholesale & retail | 2021 |
| Coombe Road Limited | Households | 2010 |
| Cooper & Hopkins Ltd | Arts & recreation | 2019 |
| Cooper Clay Estates Limited | Real estate | 2025 |
| Copella Investment Services Limited | Financial services | 2014 |
| Copers Cope Garage Limited | Extraterritorial | 1956 |
| Copper Lime Limited | Wholesale & retail | 2006 |
| Copy Shop Studios Ltd. | Administrative & support | 2018 |
| Copybee Limited | Professional & scientific | 2018 |
| Coral Spawning International Ltd | Agriculture & fishing | 2025 |
| Coral Spawning LAB Ltd | Professional & scientific | 2020 |
| Coramel Limited | Information & communication | 2026 |
| Corax Insights Ltd | Professional & scientific | 2021 |
| Corban Coffee Ltd | Manufacturing | 2018 |
| Core Belief Ltd | Education | 2019 |
| Core Marketing Partners LLP | | 2016 |
| Coronado Research Ltd | Professional & scientific | 2024 |
| Corporate Creature Productions Ltd | Information & communication | 2018 |
| Corporate Leasing & Finance Limited | Administrative & support | 2000 |
| Corporate Risk Consulting Ltd | Professional & scientific | 2021 |
| Corrion Limited | Real estate | 2003 |
| Corvallis Ltd | Construction | 2023 |
| Cost (Vacations) Limited | Administrative & support | 1999 |
| Costtron Limited | Professional & scientific | 2025 |
| Cotor Flooring Limited | Construction | 2015 |
| Cottage Farm Management Company Limited | Households | 2022 |
| Couchman Group Ltd | Financial services | 2018 |
| Country Home Renovations Ltd | Construction | 2025 |
| Country House Developments Limited | Construction | 2013 |
| Country Kids U.K. Limited | Wholesale & retail | 1990 |
| Countryview Developments Ltd | Construction | 2023 |
| Countrywise Services Limited | Administrative & support | 2018 |
| Court Lodge (Wrotham) Management Company Limited | Households | 2012 |
| Courtland Park Estate Ltd | Real estate | 2024 |
| Courtlands DV Ltd | Real estate | 2018 |
| Courtyard Gardens Management Company Limited | Real estate | 2014 |
| Couttie Limited | Extraterritorial | 2020 |
| Cova Padel Ltd | Wholesale & retail | 2026 |
| CPA (Kent) Ltd | Administrative & support | 2023 |
| CPR Tokyo UK Ltd | Professional & scientific | 2018 |
| CQC Investigations Limited | Professional & scientific | 2020 |
| CQC Readiness Ltd | Information & communication | 2026 |
| Craft Botanical Designs Limited | Professional & scientific | 2019 |
| Cranking Ltd | Wholesale & retail | 2019 |
| Cranmore Property Services Ltd | Real estate | 2023 |
| Crave Solutions Limited | Manufacturing | 2024 |
| Creacean Limited | Professional & scientific | 2023 |
| Creative Electronics Ltd | Professional & scientific | 2016 |
| Creative Flooring 2000 Limited | Construction | 2000 |
| Creative Muscle Ltd | Administrative & support | 2023 |
| Creative Nation Limited | Information & communication | 2008 |
| Creative Resins Distribution Limited | Manufacturing | 2000 |
| Creator Group Ventures Limited | Professional & scientific | 2024 |
| Creef Limited | Wholesale & retail | 1982 |
| Crescent Mechanical Services Ltd | Professional & scientific | 1997 |
| Cress Court Management Company Limited | Households | 2005 |
| Crest Living Limited | Wholesale & retail | 2011 |