| Compressor Engineering Solutions Ltd | Extraterritorial | 2009 |
| Compulogic Limited | Information & communication | 1998 |
| Compusearch Limited | Real estate | 1993 |
| Computer Doctor Limited | Information & communication | 2003 |
| Computer Services Associates (Midlands) Limited | Other services | 2002 |
| Computerword Limited | Information & communication | 1996 |
| Comtech IT Services Limited | Professional & scientific | 2010 |
| Conarium Ltd | Real estate | 2023 |
| Concannon Communications Ltd | Professional & scientific | 2012 |
| Concept 42 Limited | Professional & scientific | 2025 |
| Concept Balustrades Limited | Construction | 2000 |
| Concept Capital Group Ltd | Real estate | 2019 |
| Concept Construction & Home Improvements Ltd | Construction | 2023 |
| Concept Conversions Holdings Limited | Financial services | 2018 |
| Concept Conversions Limited | Manufacturing | 1993 |
| Concept Marketing and Distribution Limited | Wholesale & retail | 2008 |
| Concept Personnel Limited | Administrative & support | 2003 |
| Concept Print (Midlands) Limited | Administrative & support | 2004 |
| Concept Residential Ltd | Hospitality | 2022 |
| Concept Scaffolding Services Ltd | Administrative & support | 2020 |
| Concept Vehicle Management Limited | Other services | 2005 |
| Conchord Limited | Professional & scientific | 2009 |
| Concierge Club Global Limited | Administrative & support | 2023 |
| Concord Consult Limited | Professional & scientific | 2022 |
| Concorde Sports Ltd | Arts & recreation | 2025 |
| Conduit Accounting Ltd | Professional & scientific | 2024 |
| Cone Group Limited | Construction | 2017 |
| Confidence Healthcare Ltd | Health & social care | 2022 |
| Configureitdone Ltd | Construction | 2021 |
| Confistruct Limited | Construction | 2020 |
| Conglom Realty Holdings (UK) Ltd | Real estate | 2017 |
| Congregational Memorial Hall Trust (1978) Limited(The) | Education | 1978 |
| Connect ME UK Limited | Administrative & support | 2011 |
| Connect Search Limited | Administrative & support | 2010 |
| Connect Vehicle Movements Limited | Transport & logistics | 2018 |
| Connected Rapid Security Ltd | Financial services | 2026 |
| Connected Together CIC | Professional & scientific | 2013 |
| Connektivity Group Ltd | Financial services | 2022 |
| Connektivity Ltd | Information & communication | 2013 |
| Connexas Holdings Limited | Professional & scientific | 2013 |
| Connexions Care Agency Ltd | Health & social care | 2021 |
| Connikie Bowen Associates Limited | Real estate | 2021 |
| Connikie Bowen Consulting Ltd | Professional & scientific | 2024 |
| Conquest Entertainment Limited | Manufacturing | 2019 |
| Conradconrad Limited | Administrative & support | 2007 |
| Cons and Clean Limited | Wholesale & retail | 2024 |
| Consensus Medical Ltd | Administrative & support | 2019 |
| Consergo Limited | Professional & scientific | 2006 |
| CONSERVATORY4YOU Ltd | Construction | 2018 |
| Consider & Consult Ltd | Professional & scientific | 2025 |
| Consolidated Movers and Logistics Ltd | Transport & logistics | 2025 |
| Constant Equity Limited | Professional & scientific | 2016 |
| Constantia FFP Limited | Manufacturing | 1966 |
| Constantin CZR Curiers Ltd | Transport & logistics | 2026 |
| Constantin Leonard Ltd | Transport & logistics | 2026 |
| Constantin VAL Plastering Ltd | Construction | 2024 |
| Construct & Cladding Ltd | Construction | 2024 |
| Construct 7 Ltd | Construction | 2022 |
| Construct&Develop Limited | Construction | 2020 |
| CONSTRUCT4U Ltd | Construction | 2017 |
| Construction & Building Solutions Ltd | Construction | 2022 |
| Construction & Consultancy Ltd | Professional & scientific | 2010 |
| Construction Contract Commercial Projects Limited | Professional & scientific | 2014 |
| Construction Industry Services Limited | Construction | 2021 |
| Construction IS Ltd | Construction | 2025 |
| Construction Today Ltd | Construction | 2025 |
| Constructive HR Limited | Professional & scientific | 2016 |
| Consui Limited | Information & communication | 2000 |
| Consulo Compliance Ltd | Administrative & support | 2022 |
| Consulo Health & Safety Ltd | Administrative & support | 2020 |
| Consult APC Ltd | Professional & scientific | 2023 |
| Consultiva Limited | Information & communication | 2011 |
| Contabil Roman Ltd | Professional & scientific | 2024 |
| Contabilitax UK Ltd | Professional & scientific | 2024 |
| Contarenn Ltd | Wholesale & retail | 2024 |
| Content Bay Limited | Professional & scientific | 2018 |
| Content Developers Limited | Education | 2022 |
| Contextiq Ltd. | Information & communication | 2026 |
| Contourspace Ltd | Professional & scientific | 2020 |
| Contract Sentinel Limited | Information & communication | 2002 |
| Convert Build & Maintain Limited | Construction | 2025 |
| CONVERT2GREEN Limited | Manufacturing | 2006 |
| Convertimpact Ltd | Administrative & support | 2023 |
| Convex Technology Ltd | Manufacturing | 2021 |
| Convex Trading Ltd | Wholesale & retail | 2019 |
| Conveymax Ltd | Information & communication | 2026 |
| Conveyor Lines Limited | Manufacturing | 1986 |
| Convid Limited | Administrative & support | 2019 |
| Cooage Ltd | Health & social care | 2023 |
| Coodart Limited | Information & communication | 2011 |
| Coogee Electricity Ltd | Energy | 2024 |
| Cook & Columbus Ltd | Hospitality | 2010 |
| Cooked Meat Co. Limited | Manufacturing | 2010 |
| Cookie Babes UK Limited | Manufacturing | 2026 |
| Cooksley's Independent Funeral Services Limited | Other services | 2018 |
| Cool Ground Limited | Real estate | 1996 |
| Cool Quest Ltd | Households | 2024 |
| Cool Riads Limited | Hospitality | 2010 |
| Cool Space Solutions Limited | Construction | 2025 |
| Cooling Techniques Ltd | Energy | 2005 |