| City Audiology Limited | Health & social care | 2019 |
| City Barbers Greenford Ltd | Other services | 2024 |
| City Marble Ltd | Manufacturing | 2019 |
| City Properties (U.K.) Limited | Construction | 1985 |
| City Stay Suites Ltd | Real estate | 2025 |
| City Style Barber Ltd | Other services | 2023 |
| Civix Limited | Construction | 2026 |
| Clarence Gate Investment Ltd | Real estate | 2023 |
| Clarendon Professional Services Limited | Real estate | 1984 |
| Claris Housewares & Stationery Solutions Limited | Wholesale & retail | 2012 |
| Claritypath Group Ltd | Information & communication | 2025 |
| Classic Catering Services Ltd | Hospitality | 2019 |
| Clcr Limited | Construction | 2015 |
| Clean & Simple Design Limited | Professional & scientific | 2015 |
| Clean Genie London West Ltd | Administrative & support | 2018 |
| Clean Genius Ltd | Administrative & support | 2023 |
| Clean Laundry & Drycleaners Limited | Other services | 2013 |
| Cleanover Ltd | Administrative & support | 2025 |
| Clear Imports Limited | Wholesale & retail | 2025 |
| Clear Lifestyle Limited | Wholesale & retail | 2021 |
| Clearpos London Limited | Manufacturing | 2020 |
| Clearpos Ltd | Information & communication | 2020 |
| Clearwater VN Ltd | Real estate | 2021 |
| Clearway Clearances Limited | Water & waste | 2021 |
| Cleveland Anderson International Artists Ltd | Arts & recreation | 2011 |
| Click&Ship Ltd | Wholesale & retail | 2024 |
| CLICK2MOVES Ltd | Transport & logistics | 2025 |
| Clive Michael Shepherd Ltd | Extraterritorial | 2023 |
| Close Watch Elite Ltd | Administrative & support | 2025 |
| Cloud Professionals Ltd | Professional & scientific | 2022 |
| Clukp Ltd | Manufacturing | 2021 |
| CM89 Capital Ltd | Real estate | 2025 |
| CML UK Private Limited | Information & communication | 2008 |
| Cmop Limited | Administrative & support | 2024 |
| CMX Culturemetrix Group Ltd | Professional & scientific | 2026 |
| CN Concept Construction Ltd | Manufacturing | 2025 |
| Cnmz Contracts Ltd | Construction | 2025 |
| Coaching Lens Limited | Professional & scientific | 2018 |
| Cobalt Cloud Ltd | Health & social care | 2020 |
| Codegen (UK) Limited | Extraterritorial | 2006 |
| Codegen Limited | Information & communication | 2000 |
| Codegen Services Limited | Extraterritorial | 2006 |
| Codence Labs Ltd | Information & communication | 2025 |
| Coffee Beans Haven Ltd | Wholesale & retail | 2024 |
| Coleai Limited | Information & communication | 2026 |
| Collective Cashflow Ltd | Professional & scientific | 2025 |
| College Tyres Perivale Ltd | Wholesale & retail | 2013 |
| Colonel TOM Touring Limited | Arts & recreation | 2009 |
| Comestibles & Victuals FBO Ltd | Professional & scientific | 2024 |
| Comfort Engineering and Maintenance Limited | Administrative & support | 2004 |
| Comfortair Hire & Sales (UK) Limited | Other services | 1999 |
| Commercial Property 365 Limited | Real estate | 2025 |
| Community Travel CIC | Administrative & support | 2001 |
| Compact Joinery Limited | Manufacturing | 2020 |
| Compact Project Ltd | Construction | 2018 |
| Compare My Insurances TOO Limited | Financial services | 2020 |
| Compare the Suppliers Limited | Information & communication | 2020 |
| Compassion PVT Ltd | Health & social care | 2018 |
| Competitive Limited | Information & communication | 2020 |
| Completely Licensed Limited | Education | 2024 |
| Compliance World Ltd | Professional & scientific | 2022 |
| Conclusive Solutions Limited | Administrative & support | 1987 |
| Concrete United Limited | Wholesale & retail | 2020 |
| Confluence Africa Ltd | Financial services | 2022 |
| Connaught Pubs Ltd | Hospitality | 2008 |
| Connect Distribute Ltd | Transport & logistics | 2024 |
| Conought Development Ltd | Construction | 2025 |
| Conservative Friends of Israel Limited | Administrative & support | 2012 |
| Conservative India Policy Forum Ltd | Professional & scientific | 2025 |
| Consolidated Road Sea Logistics UK Ltd | Transport & logistics | 2009 |
| Consort Contractor Property Services Limited | Real estate | 2020 |
| Construction West London Ltd | Construction | 2024 |
| Consultis International Limited | Professional & scientific | 2015 |
| Contabile Limited | Administrative & support | 2016 |
| Cooll Ltd | Construction | 2015 |
| Cor-Bus DR Ltd | Wholesale & retail | 2019 |
| Cordial HR Limited | Professional & scientific | 2025 |
| Corecon Limited | Construction | 2016 |
| Coreus Ltd | Administrative & support | 2020 |
| Cork Express Ltd | Transport & logistics | 2024 |
| Cornel Utility Solutions Ltd | Construction | 2021 |
| Corporate Messengers Worldwide Limited | Transport & logistics | 2000 |
| Cosmin Constructions Ltd | Construction | 2017 |
| Cosmin Property Management Ltd | Real estate | 2020 |
| Costa Miron Limited | Construction | 2016 |
| Cotton the Motorcycle Masterpiece Ltd | Wholesale & retail | 2021 |
| Coughlan Group Ltd | Financial services | 2021 |
| Coughlan Plant Limited | Administrative & support | 2019 |
| Country Club Trading Limited | Households | 2023 |
| Cowley News Ltd | Wholesale & retail | 2019 |
| Coydon Properties Limited | Real estate | 2026 |
| Coyle Equipment Services Limited | Manufacturing | 2011 |
| CP Express Limited | Financial services | 2004 |
| Craft Studio London Ltd | Arts & recreation | 2026 |
| Craftwell Ltd | Construction | 2020 |
| Crafty Kids at Work Ltd | Wholesale & retail | 2013 |
| Crafty Kidz at Work Ltd | Wholesale & retail | 2013 |
| Crana Welding Services Limited | Construction | 2013 |
| Crave Simply Ltd | Manufacturing | 2018 |
| CRE8TIVE Sports Ltd | Arts & recreation | 2016 |