| City Tyres and Mechanics Limited | Wholesale & retail | 2025 |
| Cityline Roofing Ltd | Construction | 2025 |
| Civil Electrical & Security Ltd | Construction | 2025 |
| Clanco Franko London Ltd | Wholesale & retail | 2023 |
| Classic Miniatures Limited | Manufacturing | 1977 |
| Classy Bedrooms and Kitchens Ltd | Manufacturing | 2026 |
| Clausen Carpentry Ltd | Construction | 2018 |
| Cleanant Ltd | Wholesale & retail | 2018 |
| Cleango Services Limited | Administrative & support | 2025 |
| Cleanmysole Ltd | Administrative & support | 2023 |
| Clear OUT London Ltd | Transport & logistics | 2025 |
| Clhen Limited | Wholesale & retail | 2025 |
| Clic Amazon Ltd | Wholesale & retail | 2026 |
| Clic Tyres Ltd | Wholesale & retail | 2021 |
| Clicked Tech Ltd | Wholesale & retail | 2023 |
| Clicknest Technologies Ltd | Information & communication | 2025 |
| Clinquant Business Solutions Ltd | Professional & scientific | 2021 |
| Clockwork Accounts Limited | Professional & scientific | 2012 |
| Clothing XL Plus Limited | Wholesale & retail | 2017 |
| Cloudfinity Global Solutions Limited | Information & communication | 2023 |
| Cloudtonic Ltd | Information & communication | 2022 |
| Clued Detection Limited | Manufacturing | 2025 |
| Cluedapp Limited | Professional & scientific | 2019 |
| Cluxes Limited | Wholesale & retail | 2020 |
| CM Metalwork Services Ltd | Manufacturing | 2025 |
| Cmap Holdings Ltd | Real estate | 2026 |
| CMB Venture Ltd | Wholesale & retail | 2024 |
| CMO Interiors Ltd | Construction | 2022 |
| CMT Scaffolding Services Ltd | Construction | 2026 |
| Coalo Limited | Administrative & support | 2016 |
| Codeanode Ltd | Information & communication | 2024 |
| Coffeemax Limited | Hospitality | 2023 |
| Cognai Solutions Ltd | Information & communication | 2009 |
| Cognitive Dissidents Limited | Information & communication | 2025 |
| Coin Wallet Ltd | Information & communication | 2024 |
| Colbrans Home Solutions Ltd | Water & waste | 2023 |
| Collabrum Ltd | Construction | 2024 |
| Columnae Limited | Information & communication | 2016 |
| Comet Digital Services Ltd | Information & communication | 2023 |
| Comfort London Cars Ltd | Administrative & support | 2022 |
| Comincom Ltd | Professional & scientific | 2025 |
| Comm Tyres Ltd | Wholesale & retail | 2015 |
| Commerce Infinity Ltd | Wholesale & retail | 2025 |
| Community of Yahweh Worldwide London Limited | Other services | 1997 |
| Compare Scooters Limited | Wholesale & retail | 2020 |
| Compass Learning ARC Ltd | Education | 2025 |
| Complete Potential Ltd | Information & communication | 2022 |
| Concept Balloons Limited | Wholesale & retail | 2010 |
| Concept Inn Ltd | Administrative & support | 2025 |
| Concept Transport Ltd | Transport & logistics | 2024 |
| Concord Technologies Limited | Wholesale & retail | 2015 |
| Concrete Sealing Ltd | Construction | 2017 |
| Concur Technologies (UK) Limited | Information & communication | 1996 |
| Congs Ltd | Professional & scientific | 2025 |
| Connect Fuel Limited | Wholesale & retail | 2011 |
| Connect to Communicate Therapies Limited | Health & social care | 2026 |
| Connectboards Ltd | Information & communication | 2026 |
| Connexpos Ltd | Wholesale & retail | 2023 |
| Consolidated Logistics Services Limited | Water & waste | 2008 |
| Constalex Services Ltd | Construction | 2020 |
| Construct-Equip Limited | Real estate | 1989 |
| Consultingpro Ltd | Professional & scientific | 2024 |
| Content Connnect HQ Ltd | Information & communication | 2026 |
| Content Corp Ltd | Wholesale & retail | 2025 |
| Continuity at Infinity Ltd | Professional & scientific | 2023 |
| Cordelia Enterprise Ltd | Wholesale & retail | 2022 |
| Cordial Electrical Ltd | Construction | 2021 |
| Core Education Tuition Limited | Education | 2018 |
| Core Heating Ltd | Construction | 2022 |
| Core Services Provider Ltd | Construction | 2025 |
| Core Wholesale Ltd | Wholesale & retail | 2023 |
| Coregrid Dynamics Ltd | Transport & logistics | 2026 |
| Corereach Solutions Ltd | Wholesale & retail | 2026 |
| Cornerstone Lane Ltd | Real estate | 2025 |
| Corporate Acquisitions and Investments Ltd | Financial services | 2014 |
| Corporate Furniture & Interiors Limited | Manufacturing | 1997 |
| Correct Way Limited | Transport & logistics | 2019 |
| Cosmic DNA Ltd | Information & communication | 2021 |
| Cosmiccrowna.A Ltd | Information & communication | 2026 |
| Cosmin Plumbing and Maintenance Ltd | Construction | 2025 |
| Cosmoss Services Limited | Information & communication | 2023 |
| Cosmotrans International Ltd | Transport & logistics | 1991 |
| Cosy Burrows Limited | Real estate | 2023 |
| Covark Limited | Real estate | 2020 |
| CRAFT7 Ltd | Construction | 2024 |
| Craneconnect Ltd | Construction | 2024 |
| Crankstar UK Ltd | Wholesale & retail | 2008 |
| Crash OUT Collectibles Ltd | Wholesale & retail | 2026 |
| Crave Kart Ltd | Hospitality | 2026 |
| Cravoury Limited | Hospitality | 2025 |
| Crawfords Butchers and Catering Ltd | Wholesale & retail | 2023 |
| Creabea Ltd | Wholesale & retail | 2017 |
| Create Art London Ltd | Education | 2026 |
| Creative Art Installations Ltd | Construction | 2022 |
| Creative IT Better Ltd | Construction | 2026 |
| Creative Properties Management Ltd | Real estate | 2017 |
| Crendon Court Ltd | Real estate | 2014 |
| Creo Construction & Maintenance Limited | Construction | 2011 |
| Crestwel UK Limited | Administrative & support | 2016 |
| Crimson Comma Limited | Wholesale & retail | 2021 |