| CMJ Real Estate Limited | Real estate | 2016 |
| CMS International Network Ltd | Professional & scientific | 2022 |
| Cnrg Ltd | Professional & scientific | 2008 |
| Co-Lab Solutions Ltd | Arts & recreation | 2023 |
| Coachere Ltd | Professional & scientific | 2020 |
| Coachworks Limited | Wholesale & retail | 2013 |
| Coco Ltd | Administrative & support | 2019 |
| Cocoon AI Limited | Information & communication | 2026 |
| Coda Tech Limited | Administrative & support | 2021 |
| Coda Technology Services Ltd | Administrative & support | 2017 |
| Codesbee Ltd | Information & communication | 2021 |
| Coffee & Weights Limited | Health & social care | 2018 |
| Coffee Signs Investments Ltd | Real estate | 2025 |
| Coffee Vocabulary Limited | Other services | 2023 |
| Cohart Asbestos Disposal Limited | Water & waste | 2005 |
| Cohart Properties Ltd | Real estate | 2025 |
| Cohart Property Ltd | Real estate | 2025 |
| Cokyasar Limited | Wholesale & retail | 2026 |
| Coldharbour Road Real Estates Ltd | Real estate | 2021 |
| Colebrook Garden Services Limited | Administrative & support | 2022 |
| Coles Copying Services Limited | Administrative & support | 2006 |
| Colindale TS Ltd | Administrative & support | 2025 |
| Collectors Card CON Ltd | Wholesale & retail | 2023 |
| Collins & Collins Ltd | Professional & scientific | 2020 |
| Collins Accounting Ltd | Professional & scientific | 2015 |
| Collins Commerce Ltd | Wholesale & retail | 2022 |
| Colossal Property Ltd | Real estate | 2023 |
| Colson Construction Limited | Construction | 2025 |
| Colson Landscapes Limited | Administrative & support | 2025 |
| Come 'N' Play Cafe Limited | Arts & recreation | 2017 |
| Comfort Eats Ltd | Hospitality | 2025 |
| Comfyzone Ltd | Wholesale & retail | 2026 |
| Commandment Limited | Wholesale & retail | 2006 |
| Common Good Transport Limited | Transport & logistics | 2025 |
| Community Transport Solutions Ltd | Transport & logistics | 2020 |
| Companies That Care Limited | Professional & scientific | 2025 |
| Compare Smart Devices Limited | Extraterritorial | 2026 |
| Complete Property Maintenance & Management Services Ltd | Administrative & support | 2026 |
| Complete Waste Services London Ltd | Water & waste | 2019 |
| Completely Driven Ltd | Wholesale & retail | 2026 |
| Compton Pharma Consulting Limited | Professional & scientific | 2025 |
| Concept Building Repair Ltd | Construction | 2009 |
| Concept Cleaning Services Limited | Other services | 2009 |
| Confero Consulting Limited | Professional & scientific | 2023 |
| Conformance Group Ltd | Construction | 2020 |
| Coningsby Holdings (Hertfordshire) Limited | Professional & scientific | 2014 |
| CONNECT4 Properties Ltd | Real estate | 2018 |
| Connell Plumbing and Heating Ltd | Construction | 2018 |
| Conoley & Co Ltd | Hospitality | 2024 |
| Consilience Strategy Consulting Ltd | Professional & scientific | 2023 |
| Consilium Land (Swanley) Limited | Construction | 2021 |
| Consilium Security Systems PLC. | Professional & scientific | 1990 |
| Construction Finance Limited | Financial services | 2019 |
| Construction Resource Recycling Ltd | Water & waste | 2025 |
| Construction Solving Solutions Limited | Construction | 2017 |
| Construction Trades Academy Ltd | Education | 2024 |
| CONSTRUCTION72 Limited | Construction | 2023 |
| Constructum Code Ltd | Construction | 2023 |
| Consulting Point Ltd | Professional & scientific | 2020 |
| Contego Search Limited | Administrative & support | 2016 |
| Content Cure Ltd | Professional & scientific | 2020 |
| Contract Management Matters Limited | Administrative & support | 2017 |
| Conwaycash Ltd | Real estate | 2026 |
| Cookery School Limited | Hospitality | 2006 |
| Cool Venues Limited | Construction | 2012 |
| Cooper Paul Accountants Limited | Professional & scientific | 2025 |
| Cooper Paul Audit Limited | Professional & scientific | 2025 |
| Cooper Paul Limited | Professional & scientific | 1996 |
| Coopers Court RTM Company Ltd | Households | 2020 |
| Coopersale Hall School Limited | Administrative & support | 1998 |
| Coopersale Real Estate Ltd | Real estate | 2024 |
| Copal Properties (UK) 2021 Limited | Real estate | 2020 |
| Coperor Limited | Administrative & support | 2019 |
| Copper Beech Court (Freehold) Limited | Real estate | 2011 |
| Copper Beech Court Management Limited | Real estate | 1981 |
| Corality Ltd | Information & communication | 2024 |
| Corbbs Limited | Real estate | 2018 |
| Cormax Group Ltd | Professional & scientific | 2026 |
| Corner 5 Limited | Construction | 2011 |
| Corner House ALE & Cider Investments Limited | Hospitality | 2016 |
| Corporate Sort Limited | Professional & scientific | 2001 |
| Corporate Travel & Management Services Limited | Transport & logistics | 2007 |
| Cosmetics by Michelle Ltd | Other services | 2022 |
| Cosmoglobal Ltd | Wholesale & retail | 2025 |
| Cothaulage Ltd | Construction | 2025 |
| Cottage Flooring Limited | Construction | 2011 |
| Cottonwood Holding Ltd | Real estate | 2021 |
| Coulman Executive Cars Ltd | Transport & logistics | 2024 |
| Count Energy Distribution Limited | Wholesale & retail | 2001 |
| Country Links Ltd | Real estate | 2019 |
| Countywide Drizone Ltd | Construction | 2025 |
| Countywide Insulations Ltd | Construction | 2023 |
| Courier Team Limited | Transport & logistics | 2012 |
| Courtney Transport Services Ltd | Transport & logistics | 2017 |
| Couteau (Property) Limited | Construction | 1973 |
| Couturiosity Ltd | Manufacturing | 2021 |
| Cowley Court Freehold Limited | Households | 2010 |
| Cowley Court Management Company Limited | Households | 1997 |
| Cowley Property Investment Limited | Real estate | 2016 |
| COX Bros.(Ilford)Limited | Real estate | 1956 |