| Charlotte Emsell Limited | Professional & scientific | 2016 |
| Charm 1922 Limited | Professional & scientific | 2022 |
| Chase Partners Consulting Ltd | Professional & scientific | 2023 |
| Cherrywood Residents Limited | Households | 2007 |
| Chesfield Media Limited | Administrative & support | 2021 |
| Chilled Logistics Solutions Limited | Transport & logistics | 2017 |
| China Trading Agency Limited | Transport & logistics | 2018 |
| CHJ Group Ltd | Professional & scientific | 2020 |
| Choat & Stone Limited | Arts & recreation | 2022 |
| Christina's Childcare Limited | Health & social care | 2015 |
| Chromatic Productions Limited | Information & communication | 1988 |
| Chrono Properties Limited | Real estate | 2017 |
| Churchill House (Teddington) Ltd | Households | 2026 |
| CI Electrical & Automation Ltd | Construction | 2016 |
| Ciar Gardens Limited | Professional & scientific | 2022 |
| Ciar Property Services Ltd | Real estate | 2012 |
| Cielo Hub Ltd | Information & communication | 2025 |
| Cijc (Employers) Limited | Other services | 2010 |
| Cina Decor Ltd | Construction | 2020 |
| Cities Reloaded Ltd | Professional & scientific | 2020 |
| Citizens of the World Choir Community Interest Company | Arts & recreation | 2019 |
| City and Moon Backline Limited | Administrative & support | 2013 |
| City Docklands Limited | Extraterritorial | 2003 |
| City Vita Ltd | Real estate | 2018 |
| Cityshaks Ltd | Professional & scientific | 1999 |
| Cityshaks Residential Ltd | Real estate | 2000 |
| Civlab Ltd | Administrative & support | 2024 |
| CJH Brick Restoration Limited | Construction | 2021 |
| CJS Holistic Healthcare Ltd | Health & social care | 2020 |
| CKL Harrison Consulting Ltd | Information & communication | 2023 |
| Clair's HR Consultancy Ltd | Professional & scientific | 2019 |
| Clare Chamberlain Ltd | Administrative & support | 2018 |
| Clare Reilly HR Consultancy Ltd | Administrative & support | 2015 |
| Claremont Accounts Limited | Professional & scientific | 2020 |
| Clarendon Computer Services Limited | Information & communication | 1986 |
| Classic 500 Bookings Limited | Transport & logistics | 2010 |
| Cleanslate Communications Limited | Information & communication | 2008 |
| Clear Vista Services Ltd | Administrative & support | 2011 |
| Clinical Chemistry Consulting Ltd | Administrative & support | 2024 |
| Clive Kemp Class Guitar Ltd | Education | 2009 |
| Clive Osborne Limited | Information & communication | 2003 |
| Clothing Manufacturing Corporation Limited | Manufacturing | 2003 |
| Cloud Saas Consultants Limited | Professional & scientific | 2020 |
| Cloudbreak Capital Ltd | Financial services | 2025 |
| Cloudbreak Consulting Ltd | Professional & scientific | 2025 |
| Cloudforme Ltd. | Information & communication | 2024 |
| Cloudpresenter Limited | Information & communication | 2022 |
| Cloudqore Limited | Information & communication | 2019 |
| Cloverleaf Investment Partners Limited | Real estate | 2017 |
| CLS Consulting Ltd | Health & social care | 2023 |
| Clubhouse Management Limited | Households | 1989 |
| Clydefalls Limited | Professional & scientific | 2025 |
| Cmrgroup.Com Limited | Information & communication | 1994 |
| Co-Tech Lighting Limited | Professional & scientific | 2005 |
| Coaching With YOU LLP | | 2008 |
| Code Development Limited | Information & communication | 1997 |
| Code Genius Limited | Professional & scientific | 2018 |
| Codesource Recruitment Limited | Administrative & support | 2014 |
| COH CAM Ltd | Information & communication | 2024 |
| Colin Dean Residential Limited | Real estate | 2007 |
| Collectis Ltd | Health & social care | 2017 |
| Comarky Ltd | Professional & scientific | 2025 |
| Comby (London) Limited | Extraterritorial | 1953 |
| Commercial and General Limited | Financial services | 2000 |
| Communautic Ltd | Information & communication | 2006 |
| Communication Connection Solutions Limited | Information & communication | 2019 |
| Company Therapist Ltd. | Professional & scientific | 2020 |
| Compete Limited | Administrative & support | 1992 |
| Conder (Consulting) & Company Limited | Administrative & support | 2020 |
| Connolly House RTM Company Limited | Real estate | 2008 |
| Consilior Talent Partners Ltd | Administrative & support | 2014 |
| Consulting 26 Ltd | Information & communication | 2024 |
| Consylowe Limited | Arts & recreation | 2015 |
| Contexture Ltd | Construction | 2016 |
| Cooper Barrett Financial Services Ltd | Financial services | 2022 |
| Cooper Barrett Management Ltd | Households | 2018 |
| Cooper Faure Limited | Professional & scientific | 2006 |
| Cooperfaure Accountants Limited | Professional & scientific | 2018 |
| Corbiere Holdings UK Limited | Professional & scientific | 2020 |
| Cordell Engineering Limited | Energy | 1983 |
| Cordobaq Ltd | Professional & scientific | 2021 |
| Corinthian Chauffeur Services Ltd | Transport & logistics | 2013 |
| Corpsehire Limited | Manufacturing | 2023 |
| Cosic Accountants Limited | Professional & scientific | 2012 |
| Countryside Crop Support Ltd | Agriculture & fishing | 2025 |
| County Contracts (London) Limited | Wholesale & retail | 2002 |
| Coverdale Lodge Limited | Households | 1982 |
| CPM Education Limited | Education | 2026 |
| Cramio Ltd | Education | 2026 |
| Cranbrook Court Management Limited | Households | 1987 |
| Crave Healthy Food Ltd | Manufacturing | 2019 |
| Crea Marketing Ltd | Professional & scientific | 2021 |
| Cream Talent Management Limited | Other services | 2023 |
| Create Partners Ltd | Construction | 2019 |
| Creative Install. Home Automation Limited | Other services | 2012 |
| Creator Capital Partners Ltd | Administrative & support | 2025 |
| Crebillie Consulting Limited | Professional & scientific | 2020 |
| Crescent Kitchen London Limited | Wholesale & retail | 2022 |
| Crescent Publishing Limited | Information & communication | 2012 |
| Crew Teddington Ltd | Other services | 2025 |