| Connected Property Services Ltd | Administrative & support | 2022 |
| Connectedbycommerce Ltd | Professional & scientific | 2023 |
| Connectere Limited | Real estate | 2022 |
| Connecting Culture Limited | Professional & scientific | 2009 |
| Connectworld Limited | Information & communication | 2025 |
| Conneely Construction Ltd | Construction | 2006 |
| Conquer and Learn Limited | Education | 2004 |
| Conscious Coffee Grinders Limited | Wholesale & retail | 2025 |
| Conspiracy (Multimedia) Limited | Manufacturing | 1997 |
| Constantine Construct Solution Ltd | Construction | 2015 |
| Constructaa Ltd | Information & communication | 2024 |
| Construction Brickwork Ltd | Construction | 2014 |
| Construction Edge Ltd | Construction | 2025 |
| Constructvio Limited | Construction | 2021 |
| Consult 24/7 Ltd | Wholesale & retail | 2011 |
| Consulting by Regal Ltd | Professional & scientific | 2024 |
| Consulting for IT Limited | Information & communication | 1992 |
| Consultoria Ltd | Professional & scientific | 2014 |
| Consumerly Limited | Wholesale & retail | 2022 |
| Contax Direct Limited | Professional & scientific | 2016 |
| Contempo Living Ltd | Wholesale & retail | 2022 |
| Continental Group Logistics UK Limited | Transport & logistics | 2022 |
| Contortionworks Limited | Education | 2018 |
| Contracting Made Easy Ltd | Administrative & support | 1998 |
| Controlled Damage Solutions Limited | Professional & scientific | 2022 |
| Conversionmax Limited | Professional & scientific | 2020 |
| Convoy 365 Ltd | Transport & logistics | 2023 |
| Coochani Musk Ltd | Wholesale & retail | 2020 |
| Cooking and Crafts Limited | Education | 2025 |
| Cool Giving UK Ltd | Professional & scientific | 2025 |
| Coolmore Capital Limited | Real estate | 2021 |
| Coolturk Haulage Limited | Transport & logistics | 2018 |
| Copiers Direct UK Limited | Manufacturing | 2014 |
| Coping Through Therapy Ltd | Health & social care | 2026 |
| Coplon Limited | Professional & scientific | 2010 |
| Copmar Limited | Professional & scientific | 2025 |
| Copnor Recruitment Limited | Administrative & support | 2006 |
| Coradvice Ltd | Professional & scientific | 2019 |
| Corby Service Station Limited | Wholesale & retail | 2005 |
| Cordouan Health Limited | Information & communication | 2022 |
| Core Horizon Ltd | Financial services | 2024 |
| Cormgreen Limited | Professional & scientific | 2016 |
| Corneliu Brickwork Ltd | Construction | 2014 |
| Corner Point Investment Ltd | Administrative & support | 2014 |
| Cornwall Estates Limited | Real estate | 2003 |
| Coronavirus Cleaning Products Ltd | Administrative & support | 2020 |
| Coronavirus Deep Cleaning Services Ltd | Administrative & support | 2020 |
| Corrigan Developments Limited | Construction | 2013 |
| Corte Velho Limited | Hospitality | 2001 |
| Cosido Ltd | Professional & scientific | 2024 |
| Cosim Ltd | Construction | 2018 |
| Cosimo Trade Limited | Professional & scientific | 2019 |
| Cosmessex Beauty Ltd | Other services | 2022 |
| Cosmessex of Brentwood Ltd | Other services | 2019 |
| Cosmetics Elegance Ltd | Wholesale & retail | 2024 |
| Cosmo Trans Services Ltd | Transport & logistics | 2016 |
| Cosphil Healthcare Providers Ltd | Health & social care | 2018 |
| Cost Effective Marketing Ltd | Information & communication | 2007 |
| Costa Brothers Ltd | Construction | 2023 |
| Costa Tanz Limited | Other services | 2020 |
| Costa@Thomas Ltd | Construction | 2025 |
| Costea Ltd | Construction | 2011 |
| Costi Building Limited | Construction | 2014 |
| Costi Cars Limited | Wholesale & retail | 2024 |
| Cosy Home for YOU Ltd | Real estate | 2022 |
| Cotillo Limited | Arts & recreation | 2013 |
| Cotswold & Crown Limited | Wholesale & retail | 2024 |
| Cottage Chicken Express Ltd | Hospitality | 2025 |
| Cottingham Advisory Ltd | Information & communication | 2018 |
| Cottonham RTM Company Limited | Households | 2013 |
| Couch Chillin Lounge Livin Ltd | Wholesale & retail | 2024 |
| Countercurrent Limited | Information & communication | 2025 |
| Country House Designs Limited | Wholesale & retail | 2015 |
| Coupe Properties Ltd | Real estate | 2013 |
| Courtgate (Mill Hill) Management Company Limited | Real estate | 2002 |
| Cova Property Services Limited | Real estate | 2021 |
| Covea Construction Ltd | Construction | 2026 |
| Covenant Advisory CIC | Professional & scientific | 2020 |
| Covered Accessories Westfield Ltd | Real estate | 2021 |
| Covered Repairs & Phone Covers Ltd | Wholesale & retail | 2018 |
| Coverseal Limited | Real estate | 2000 |
| Cowlkirk Limited | Construction | 1972 |
| Coxshall Lodge Management Limited | Hospitality | 2009 |
| Cozway Limited | Wholesale & retail | 2020 |
| CPH Railway Services Limited | Construction | 2017 |
| CPK Hotels Limited | Hospitality | 1967 |
| CPO Engineering Ltd | Construction | 2020 |
| Crafty Carpenters Ltd | Professional & scientific | 2025 |
| Craig Barrell Podiatry Ltd | Health & social care | 2018 |
| Cranbourn Ltd | Wholesale & retail | 2026 |
| Crane International Limited | Real estate | 1996 |
| Cranmer Investments Limited | Real estate | 2022 |
| Cranny&Co. Ltd. | Professional & scientific | 2025 |
| Crave Desserts Ltd | Hospitality | 2026 |
| Craven Court Ltd | Real estate | 2005 |
| CRE Services Ltd | Transport & logistics | 2025 |
| Creative Arab Scents Limited | Wholesale & retail | 2024 |
| Creative Bytes Limited | Administrative & support | 1984 |
| Creative Corridor Holding Ltd | Hospitality | 2024 |
| Creative Gardens & Landscapes Limited | Administrative & support | 2010 |