| Citygate Apartments Limited | Real estate | 2007 |
| Civicstone Capital Limited | Financial services | 2026 |
| Clare Court Residents (Northwood) Limited | Real estate | 2012 |
| Claren Consulting Limited | Professional & scientific | 2013 |
| CLARITY2 Management Ltd | Professional & scientific | 2011 |
| Clean Farm Limited | Wholesale & retail | 2012 |
| Cleaners END of Tenancy Cleaning Ltd | Administrative & support | 2026 |
| Cleanora END of Tenancy Cleaning Ltd | Administrative & support | 2026 |
| Clear Bridge Group Limited | Real estate | 2018 |
| Clearview Developments Limited | Construction | 1994 |
| Clearview Holdings Ltd | Professional & scientific | 2019 |
| Clearview Homes (Carew Road) Limited | Real estate | 2016 |
| Clearview Homes (Horton Road) Ltd | Construction | 2014 |
| Clearview Homes (Sutton Court Road) Limited | Construction | 2016 |
| Clearview Homes (Western Avenue) Ltd | Real estate | 2016 |
| Clearview Homes Limited | Construction | 1991 |
| Clearview House Limited | Real estate | 2016 |
| Clearview Property Group Limited | Construction | 2018 |
| Clearview Residential (Bourne Court) Limited | Construction | 2018 |
| Clearview Residential (Crooked Billet) Limited | Construction | 2018 |
| Clearview Residential (Cunningham Park) Limited | Construction | 2016 |
| Clearview Residential (London Road) Limited | Construction | 2019 |
| Clearview Residential Ltd | Construction | 2017 |
| Clifford Consulting Limited | Professional & scientific | 2010 |
| Clifton Gate Development Limited | Construction | 2022 |
| Clifton House (Northwood) Management Company Limited | Households | 2021 |
| Clive Johnson Consulting Limited | Professional & scientific | 2018 |
| Cloister Properties Limited | Real estate | 2019 |
| Clou Engineering Ltd | Construction | 2014 |
| Clou Properties Ltd | Real estate | 2022 |
| Cloud Nine MI Ltd | Information & communication | 2011 |
| Club Coco Coffee Ltd | Hospitality | 2026 |
| Cmcg Financial Limited | Professional & scientific | 2010 |
| Cmcl Limited Partnership | | 2016 |
| CNX Capital Limited | Professional & scientific | 2014 |
| Coastal Dentacare Ltd | Health & social care | 2019 |
| Cochrane Leadership Development Limited | Professional & scientific | 2022 |
| Cocoyaya UK Ltd | Wholesale & retail | 2022 |
| Codet Construction Limited | Extraterritorial | 2021 |
| Codhaddock Limited | Hospitality | 2025 |
| Colindale Estates Limited | Real estate | 2006 |
| Collingwood House Holding Ltd | Real estate | 2026 |
| Coln River Lodges Limited | Households | 2011 |
| Columbia Executive Coaching Limited | Administrative & support | 2015 |
| Comm SI Networks Limited | Information & communication | 2004 |
| Community Healthcare Solutions Ltd | Health & social care | 2023 |
| Community Support Action Ltd | Other services | 2026 |
| Compare Dynamics Ltd | Administrative & support | 2018 |
| Complete Accounting Services Limited | Professional & scientific | 2008 |
| Complete Golfer Limited | Administrative & support | 2007 |
| Complete Space Ltd | Professional & scientific | 2018 |
| COMPLIANCE2AML Limited | Professional & scientific | 2023 |
| Complylens Limited | Information & communication | 2023 |
| Comvec Properties Limited | Construction | 1993 |
| Concert Square Management Company 2010 Limited | Real estate | 2010 |
| Concord IT Services Ltd | Information & communication | 2006 |
| Congress Team International (UK) Limited | Administrative & support | 1983 |
| Coninca Ltd | Wholesale & retail | 2023 |
| Coniston Estates Ltd | Real estate | 2021 |
| Consilia Ltd | Health & social care | 2021 |
| Constance Hathaway Limited | Real estate | 2014 |
| Construction Contract Consulting Limited | Construction | 2016 |
| Constructional Exports (London) Limited | Real estate | 1966 |
| Contour Design Studio Ltd | Professional & scientific | 2023 |
| Cooksparaphernalia Limited | Wholesale & retail | 2004 |
| Coolhall Limited | Administrative & support | 1992 |
| Copper Beech Management Limited | Real estate | 1990 |
| Copse Wood Investments Limited | Real estate | 2004 |
| Core Gym Training Limited | Arts & recreation | 2020 |
| Corebridge Consulting Limited | Information & communication | 2025 |
| Corfton Properties Limited | Hospitality | 2012 |
| Corsega Productions Ltd | Other services | 2017 |
| Cosmetic Smile Studio Limited | Health & social care | 2019 |
| Cosmin Palamariu Ltd | Construction | 2016 |
| Coste + Beno Ltd | Construction | 2020 |
| COUNSEL4U Ltd | Professional & scientific | 2025 |
| Country Compost Limited | Water & waste | 2000 |
| Courtlink Ltd | Construction | 2025 |
| CP Corporate Consulting Limited | Professional & scientific | 2016 |
| CPI Consultants Limited | Professional & scientific | 2023 |
| Creators of Design International Limited | Real estate | 2017 |
| Creators of Design Limited | Extraterritorial | 2021 |
| Credit and Political Risk Consultants Ltd | Financial services | 2010 |
| Crestbury Investments 1 Limited | Real estate | 2018 |
| Crimsonplace Limited | Wholesale & retail | 2000 |
| Cristal DE Settat (UK) Limited | Real estate | 2000 |
| Crossberry Limited | Real estate | 1981 |
| Crow Fourteen Limited | Real estate | 2020 |
| Crunch Concepts Limited | Financial services | 2025 |
| Crusher Hire UK Limited | Construction | 2014 |
| Crystal Clear Property Management Ltd | Construction | 2015 |
| CS Drylining Ltd | Construction | 2011 |
| Cube Telecom Services Ltd | Information & communication | 2019 |
| Cubelynx Limited | Professional & scientific | 2019 |
| Cubix Ltd | Information & communication | 2022 |
| Cuddly Cubs Montessori Limited | Health & social care | 2023 |
| Cunningham Equine Services Ltd | Agriculture & fishing | 2024 |
| Cuproban Systems Limited | Professional & scientific | 1983 |
| Cura Advanced Technologies Limited | Information & communication | 2014 |
| Cura Systems International Limited | Information & communication | 2012 |