| Combustion Partners Limited | Professional & scientific | 2016 |
| Comco Limited | Information & communication | 1994 |
| Comet Homes Limited | Construction | 2021 |
| Comfort D Ltd | Education | 2014 |
| Comic Book Auctions Limited | Arts & recreation | 1992 |
| Commerce Catalyst Ltd | Information & communication | 2024 |
| Commonside Healthcare Limited | Wholesale & retail | 2025 |
| Commz Ltd | Information & communication | 2010 |
| Company 360 Ltd | Wholesale & retail | 2019 |
| Compass Event Services Ltd | Transport & logistics | 2025 |
| Complete Aquariums Limited | Wholesale & retail | 2013 |
| Complete Consultancy Limited | Administrative & support | 2015 |
| Comsys LLP | | 2012 |
| Concept Patisserie Limited | Manufacturing | 2018 |
| Cone Entertainment Limited | Information & communication | 2007 |
| Confident Cubs Limited | Health & social care | 2025 |
| Conix.Ai Ltd | Information & communication | 2021 |
| Conjuvo Ltd | Information & communication | 2023 |
| Connect Travels & Tours Ltd | Administrative & support | 2025 |
| Connvertex Technologies UK Limited | Information & communication | 2023 |
| Conrad Bell Associates Limited | Administrative & support | 2002 |
| Conscious Exchange Limited | Professional & scientific | 2025 |
| Consilior Limited | Professional & scientific | 2013 |
| Constant Gardener Limited | Administrative & support | 2013 |
| Constantine Properties Limited | Real estate | 2019 |
| Construction Centre Ltd | Construction | 2012 |
| Consultancy House Limited | Professional & scientific | 2003 |
| Consultancy World Limited | Other services | 2019 |
| Consultant Pain Management Ltd | Health & social care | 2011 |
| Consultare Solutions Ltd | Construction | 2024 |
| Consulting by Waterfords Limited | Professional & scientific | 2015 |
| Consulting Z Limited | Information & communication | 2022 |
| Controls Engine Ltd | Professional & scientific | 2017 |
| Coobail Real Estates Limited | Real estate | 2023 |
| Cookie Cloud Limited | Hospitality | 2024 |
| Coomtata Ltd | Health & social care | 2021 |
| Cooper Associates Financial Ltd | Professional & scientific | 2023 |
| Cooplay Ltd | Administrative & support | 2023 |
| Coordinator Ltd | Administrative & support | 2025 |
| Coppersun Creations Ltd | Hospitality | 2024 |
| Copyrightimage Limited | Professional & scientific | 2003 |
| Coral Pharmacy Limited | Wholesale & retail | 2003 |
| Coranwat Limited | Wholesale & retail | 1979 |
| Corato Holdings Limited | Energy | 2010 |
| Core Team Limited | Financial services | 2019 |
| Coredata Labs Limited | Information & communication | 2025 |
| Coren's Canines Ltd | Other services | 2019 |
| CORETE4M Ltd | Professional & scientific | 2019 |
| Cosec Management Ltd | Professional & scientific | 2000 |
| Cosmetic Solutions Properties Ltd | Real estate | 2014 |
| Cosmetic Solutions UK Limited | Financial services | 2008 |
| Cosmic Reliable Limited | Information & communication | 2014 |
| Cossac Ltd | Other services | 2014 |
| Costcloud Ltd | Professional & scientific | 2023 |
| Coucal Property Ltd | Real estate | 2009 |
| Cougar 1 Limited | Real estate | 2015 |
| Countrywide Estates Ltd | Real estate | 2025 |
| Cowling Security Ltd | Administrative & support | 2010 |
| Cowper Road Developments Limited | Real estate | 2026 |
| Cozybricks Ltd | Real estate | 2020 |
| CP Rowlands Limited | Financial services | 2021 |
| CR Handon Ltd | Hospitality | 2025 |
| Craft Design Construction Ltd | Wholesale & retail | 2012 |
| Craftmark Homes Limited | Construction | 2025 |
| Crasna Foods Ltd | Wholesale & retail | 2014 |
| Crasnacumar Enterprise Ltd | Real estate | 2023 |
| Cray Hill Pharmaceuticals Limited | Administrative & support | 2011 |
| Crbl Investments Limited | Real estate | 2022 |
| CRC Removal Consultants Limited | Transport & logistics | 2017 |
| Crcg Holdings Limited | Financial services | 2024 |
| Create Gifts Ltd | Wholesale & retail | 2022 |
| Create Innovate Ltd | Extraterritorial | 2018 |
| Createmore Healthcare Limited | Wholesale & retail | 2021 |
| Createmore Investments Limited | Real estate | 2022 |
| Creation Click Ltd | Administrative & support | 2013 |
| Creative Channels Ltd | Administrative & support | 2017 |
| Creative EYE Media Limited | Manufacturing | 2012 |
| Creative Secure Solutions Limited | Administrative & support | 2022 |
| Creative VIZ Ltd | Professional & scientific | 2025 |
| Creativedge Bespoke Furniture Limited | Manufacturing | 2013 |
| Creativity Rooms Ltd | Professional & scientific | 2023 |
| Credibl Ltd | Professional & scientific | 2020 |
| Cremex (UK) Ltd | Real estate | 2014 |
| Crescent IT Consulting Ltd | Information & communication | 2012 |
| Cricklewood Holdings Ltd | Real estate | 2024 |
| Cristian Construction Paving Ltd | Construction | 2024 |
| CRM Books Ltd | Professional & scientific | 2019 |
| Crocker Hickey Ltd. | Real estate | 2017 |
| Crooked Kitchens Limited | Hospitality | 2017 |
| Crosbie Care Limited | Health & social care | 2012 |
| Crossbridge Global Ltd | Wholesale & retail | 2026 |
| Crosshatch Projects Ltd | Construction | 2020 |
| Crossway Colindale (Block a) Management Company Limited | Households | 1992 |
| Crossway Colindale (Block B) Management Company Limited | Households | 1992 |
| Crossway Colindale (Block C) Management Company Limited | Households | 1992 |
| Crown Stays Ltd | Real estate | 2026 |
| Crown Stone Developments Limited | Construction | 2021 |
| Crownstone Cyber Security (UK) Limited | Information & communication | 2025 |
| Crownvent Limited | Real estate | 2000 |
| Crucible Bar Collective Limited | Professional & scientific | 2017 |