| Connections (Interiors) Limited | Construction | 1990 |
| Connections South East Ltd | Construction | 2021 |
| Connor Hayes Consulting Limited | Professional & scientific | 2024 |
| Connor Holdings Limited | Real estate | 2022 |
| Connor Mitchell Limited | Arts & recreation | 2025 |
| Conridge Limited | Hospitality | 2005 |
| Consensus Distributors LLP | | 2008 |
| Consentium Consulting Limited | Professional & scientific | 2014 |
| Conserve Paintings Ltd | Arts & recreation | 2025 |
| Considine London LLP | | 2025 |
| Consors Developments Limited | Construction | 2019 |
| Consors Group Limited | Financial services | 2023 |
| Consors Investments Limited | Real estate | 2023 |
| Construct 19 Limited | Construction | 2019 |
| Construct, Concrete Structures Group Limited | Construction | 1994 |
| Construction Compliance Ltd | Construction | 2026 |
| Construction General Masters Ltd | Construction | 2021 |
| Consultantbox Ltd | Administrative & support | 2012 |
| Consultatio Limited | Professional & scientific | 2022 |
| Consumer Watch Ltd | Other services | 2014 |
| Contar Resins Limited | Manufacturing | 2015 |
| Conteh Collection Limited | Real estate | 2022 |
| Continental Financial Management Limited | Administrative & support | 1999 |
| Continente Cafe Limited | Hospitality | 2020 |
| Contract Transport Services Limited | Transport & logistics | 2012 |
| Convurt Smart Systems Ltd | Construction | 2019 |
| Cookie Design & Print Limited | Professional & scientific | 2013 |
| Cooks Carriages Limited | Other services | 2018 |
| Cooks Property Holdings Limited | Real estate | 2020 |
| Cool & Cute Ltd | Wholesale & retail | 2022 |
| Cool Bride Co Limited | Wholesale & retail | 2025 |
| Coolair Installations Limited | Construction | 2011 |
| Coole Investments Ltd | Real estate | 2025 |
| Cooper & Parks Financial Services Limited | Financial services | 2005 |
| Cooper Lingard Solicitors Limited | Professional & scientific | 2022 |
| Cooper Sheldrick Ltd | Financial services | 2015 |
| Cooper Steel Ltd | Construction | 2020 |
| Coopers Coins & Medals Ltd | Wholesale & retail | 2026 |
| Coopers Concrete Structures Ltd | Construction | 2019 |
| Coopers Plumbing Services Ltd | Construction | 2025 |
| Coopers Roofing Limited | Construction | 2025 |
| Copping Joyce Surveyors Limited | Administrative & support | 2013 |
| Copyright Repro Solutions Ltd | Information & communication | 2019 |
| Coran O Sullivan Construction Consultancy Limited | Professional & scientific | 2012 |
| Corby Property Group Ltd | Financial services | 2025 |
| Corby Property Limited | Real estate | 2025 |
| Cordbray Management Ltd | Administrative & support | 2006 |
| Core Fire Security Limited | Administrative & support | 2025 |
| Core FSI Ltd | Construction | 2024 |
| Cori-Seal Systems Ltd | Construction | 2019 |
| Corinium Limited | Professional & scientific | 2002 |
| Corniche Ventures Ltd | Financial services | 2024 |
| Cornwall Supplies Cleaning Limited | Other services | 2012 |
| Corporation Fire Ltd | Public administration | 2010 |
| Corringham Bull Public House Ltd | Extraterritorial | 2024 |
| Cosmetic Laser Removal Ltd | Extraterritorial | 2012 |
| Costello Estates Limited | Real estate | 2022 |
| Costs Worldwide Ltd | Construction | 2021 |
| Costy's Electrical Services Ltd | Construction | 2019 |
| Cosy Coffehouse Ltd | Hospitality | 2025 |
| Cotswold Aesthetics Clinic Ltd | Health & social care | 2022 |
| Cotswold Aviation Consultants Ltd | Professional & scientific | 2019 |
| Cottle Properties Limited | Real estate | 2024 |
| Countryside Style Limited | Construction | 2016 |
| County Air Conditioning Ltd | Construction | 2025 |
| County Building and Property Ltd | Administrative & support | 2016 |
| County Group Services Limited | Construction | 2026 |
| County Water Testing Ltd | Professional & scientific | 2025 |
| Courage Energy (U.K.) Limited | Mining & quarrying | 1997 |
| Courageous Leaders Limited | Professional & scientific | 2024 |
| Course Academy Ltd | Education | 2025 |
| Covent Garden Naturals Limited | Health & social care | 2017 |
| Cover Call Building Services Limited | Construction | 1996 |
| Coversearch Ltd | Real estate | 2023 |
| Coverstaff Limited | Administrative & support | 1982 |
| Cowboys & Ranchers Ltd | Hospitality | 2025 |
| CP Property Solutions Ltd | Construction | 2017 |
| Cpdr Limited | Manufacturing | 2023 |
| Cra-Con Consulting Limited | Professional & scientific | 2024 |
| Craft Solutions Essex Limited | Construction | 2026 |
| Cramak Limited | Professional & scientific | 2025 |
| Crandon (M & E) Limited | Construction | 2008 |
| Cranfield Partners Limited | Professional & scientific | 2010 |
| Crashworks Business Consulting Limited | Professional & scientific | 2025 |
| Crave Concessions Ltd | Hospitality | 2024 |
| Crays Hill 1 Ltd | Financial services | 2025 |
| Crays Hill Ltd | Construction | 2025 |
| CRB Financial Ltd | Financial services | 2023 |
| Creams and Coffees Limited | Hospitality | 2020 |
| Createpay Group Holdings Limited | Financial services | 2026 |
| Createpay Merchant Services Limited | Administrative & support | 2026 |
| Creative Commercial Contracts & Procurement Ltd | Professional & scientific | 2026 |
| Creative Homes (Essex) Limited | Construction | 2022 |
| Creative Plastic Design Limited | Manufacturing | 2019 |
| Creative Woodworks (Joinery) Ltd | Construction | 2023 |
| Creators and Makers Limited | Information & communication | 2018 |
| Credit Landscapes Ltd | Financial services | 2003 |
| Crest Select Limited | Real estate | 2026 |
| Cricketfield Car Sales Ltd | Administrative & support | 2019 |
| Cricketfield Leigh Ltd | Households | 2019 |