| Cithara Ltd | Information & communication | 2018 |
| Citrus Valley Properties Ltd | Real estate | 2023 |
| City Calling Limited | Administrative & support | 2011 |
| City Diggs Ltd | Hospitality | 2016 |
| CJ2 Limited | Professional & scientific | 2005 |
| Cjan Ltd | Real estate | 2018 |
| CJK Digital Ltd | Information & communication | 2014 |
| Claddagh Investments Limited | Real estate | 2015 |
| Claddagh Residential Limited | Real estate | 2017 |
| Claimwhys Limited | Financial services | 2010 |
| Classic Autos of Kings Langley LLP | | 2009 |
| Classic PM LLP | | 2019 |
| Clay Atelier Limited | Wholesale & retail | 2019 |
| Clevercore Limited | Information & communication | 2023 |
| Cloontagh Plant Ltd | Construction | 2020 |
| Clutch Property Limited | Financial services | 2023 |
| CNS Energy Limited | Energy | 2024 |
| CNS Productions Limited | Information & communication | 2021 |
| Coachingme Limited | Arts & recreation | 2022 |
| Cobweb Rigging Limited | Construction | 2003 |
| Coda Consulting Services Ltd | Professional & scientific | 2025 |
| CODE365 Ltd | Information & communication | 2011 |
| Cognivance Limited | Professional & scientific | 2025 |
| Colin Clarke Engineering Ltd | Wholesale & retail | 2021 |
| Commonwood House Management 1999 Limited | Real estate | 1999 |
| Commonwood House Management Limited | Households | 1983 |
| Comprehensive Commercial Services Limited | Wholesale & retail | 1995 |
| Con-Sole Group Ltd | Manufacturing | 2026 |
| Concept Heating Investments Ltd | Real estate | 2024 |
| Concept Heating Ltd | Construction | 2022 |
| Concert Bay Limited | Professional & scientific | 2004 |
| Concord MET Construction Limited | Construction | 2026 |
| Concord Metropolitan Construction (UK) Limited | Construction | 1990 |
| Connected Paths International Ltd | Professional & scientific | 2026 |
| Conserva Children Services Ltd | Health & social care | 2023 |
| Constantine Freehold Limited | Real estate | 2008 |
| Constructenergy Limited | Professional & scientific | 1980 |
| Contullich Energy Storage Limited | Energy | 2022 |
| Coopers Grange (Bishops Stortford) Resident Management Company Ltd | Households | 2021 |
| Coora Plant & Civils (CPC) Limited | Construction | 2020 |
| Cordelicious Limited | Information & communication | 2015 |
| Cordoba Freehold Ltd | Real estate | 2024 |
| Corey Seaton Limited | Other services | 2022 |
| Cossart,Gordon and Co.Limited | Wholesale & retail | 1907 |
| Court Club Ltd | Wholesale & retail | 2024 |
| Court Disaster Limited | Health & social care | 2007 |
| CR Design Works Ltd | Professional & scientific | 2024 |
| Crado Ltd | Professional & scientific | 2025 |
| Crafted Jewellery Limited | Wholesale & retail | 2017 |
| Creative Duce Limited | Professional & scientific | 2021 |
| Creekside Capital Ltd | Professional & scientific | 2019 |
| Cremello Connect Limited | Administrative & support | 2020 |
| Critical Fire Solutions Ltd | Public administration | 2021 |
| Croxley Builders (West & Sons) Limited | Construction | 2006 |
| Crystalline Green Ltd. | Information & communication | 2011 |
| CSE Kent Limited | Financial services | 2010 |
| Cube HR Limited | Professional & scientific | 2015 |
| Custom Made Web Solutions Ltd | Professional & scientific | 2024 |
| Custom Waterjet Cutting Limited | Professional & scientific | 2015 |
| Cvec Ltd | Information & communication | 2012 |
| CWT Services Limited | Other services | 2017 |
| CXC Contracting UK Ltd | Professional & scientific | 2021 |
| CXC Global Emea UK Limited | Professional & scientific | 2016 |
| Cyber Aegis Limited | Administrative & support | 2016 |
| Cyprus Property Limited | Construction | 2005 |
| D Bunker & SON Limited | Construction | 2011 |
| D&P Decorating Group Ltd | Construction | 2018 |
| D.W.S Rigging Services Ltd | Construction | 2011 |
| D8TA Genie Limited | Professional & scientific | 2015 |
| DAN & SI Property Ltd | Real estate | 2024 |
| Darboe Jula & Co Ltd | Professional & scientific | 2014 |
| Data Nova Analytics Limited | Information & communication | 2024 |
| Datasys I.T. Services Limited | Information & communication | 2002 |
| David Hicks Limited | Information & communication | 2013 |
| Davisoft Limited | Transport & logistics | 2019 |
| Decisive Fitness Limited | Wholesale & retail | 2019 |
| Decorte Future Industries Ltd | Information & communication | 2019 |
| Deether Project and Property Consultants Limited | Real estate | 2021 |
| Delatronics Ltd | Other services | 2025 |
| Delcovo Ltd | Professional & scientific | 2020 |
| Denzell Downs Limited | Construction | 2010 |
| Designer Electrical Services Limited | Manufacturing | 2004 |
| Despacito Limited | Information & communication | 2017 |
| Detailer Built Ltd | Construction | 2024 |
| DF Contracts Limited | Professional & scientific | 2017 |
| DGR Electrical Services Ltd | Construction | 2022 |
| DHJ 01 Limited | Construction | 2023 |
| Digital Dust Marketing Ltd | Professional & scientific | 2023 |
| Digital Photography NOW Limited | Professional & scientific | 2003 |
| Dockies Ltd | Hospitality | 2024 |
| Donkey Sports Merchandise Ltd | Manufacturing | 2022 |
| Dootydoo Limited | Information & communication | 2013 |
| Dorje Limited | Professional & scientific | 2019 |
| Drago Engineering Limited | Professional & scientific | 2025 |
| Drawntear Limited | Wholesale & retail | 2019 |
| Dreachmhor Wind Farm Limited | Energy | 2013 |
| Dreamuni Connect Ltd | Education | 2025 |
| DRH Groundworks Limited | Construction | 2013 |
| Dunbeg South Holdings Limited | Financial services | 2025 |
| Dunmill Energy Storage Limited | Energy | 2022 |