| Clocklow Limited | | 1984 |
| Clockwise Associates Limited | Real estate | 2002 |
| Clodane Management Limited | Health & social care | 2015 |
| Clojam Limited | Information & communication | 2020 |
| Clonmel Building Contractors Limited | Construction | 1997 |
| Close UP Limited | Information & communication | 2021 |
| Closicart Ltd | Wholesale & retail | 2025 |
| Closing Delta Ltd | Professional & scientific | 2020 |
| Clothbury London Ltd | Wholesale & retail | 2026 |
| Clothing Express Limited | Wholesale & retail | 2000 |
| Cloud Accountancy 247 Ltd | Professional & scientific | 2025 |
| Cloud AI Tech Limited | Information & communication | 2021 |
| Cloud Annotation Limited | Information & communication | 2024 |
| Cloud Army UK Limited | Information & communication | 2018 |
| Cloud Basket Ltd | Wholesale & retail | 2026 |
| Cloud Bookkeeping Limited | Professional & scientific | 2010 |
| Cloud Fours Technologies Ltd | Information & communication | 2022 |
| Cloud Ilearn Limited | Education | 2012 |
| Cloud Infra Solutions Ltd | Information & communication | 2026 |
| Cloud Solutions IT Limited | Information & communication | 2014 |
| Cloud Space Solutions Ltd | Information & communication | 2020 |
| Cloud Tech Consulting Ltd | Information & communication | 2014 |
| Cloudanceproductions Ltd | Manufacturing | 2026 |
| Cloudbase Aviation Services Limited | Education | 1994 |
| Cloudberry Living Limited | Wholesale & retail | 2007 |
| Cloudcom Associates Limited | Information & communication | 2011 |
| Cloudeats Ltd | Wholesale & retail | 2026 |
| Cloudfirst Advisory & Consulting Ltd | Information & communication | 2025 |
| Cloudloom Ltd | Information & communication | 2020 |
| Cloudman Services Ltd | Professional & scientific | 2025 |
| Cloudomation Ltd | Information & communication | 2017 |
| Cloudsculpts Solutions Ltd | Information & communication | 2014 |
| Cloudtail Ltd | Wholesale & retail | 2024 |
| Cloudtec (UK) Ltd | Construction | 2013 |
| Cloudthat Technologies UK Limited | Information & communication | 2021 |
| Cloudy Hill Films Ltd | Information & communication | 2024 |
| Cloughabreeda Ltd | Real estate | 2019 |
| Cloutech Innovations Ltd | Information & communication | 2018 |
| Cloutman Harris Nixon LLP | | 2020 |
| Clover Tech Consulting Limited | Administrative & support | 2021 |
| Cloverfields Holding Limited | Financial services | 2024 |
| Cloverleaf Security Limited | Administrative & support | 2004 |
| Clrs Investment Ltd | Financial services | 2017 |
| CLS Airline Supplies Limited | Hospitality | 2006 |
| Club 90S Ltd | Wholesale & retail | 2025 |
| Club LA Santa Limited | Extraterritorial | 1987 |
| Clubdeal Limited | Information & communication | 1996 |
| Clunas Consultants Limited | Professional & scientific | 2011 |
| CLW Accountancy & Bookkeeping Services Ltd | Professional & scientific | 2021 |
| Clyapp Ltd | Information & communication | 2020 |
| CM Advantage Limited | Information & communication | 2011 |
| CM Cloud & Devops Ltd | Information & communication | 2019 |
| CM Leisure and Hospitality Services Ltd | Other services | 2025 |
| CM Northern Heights Limited | Financial services | 2014 |
| CM Train Ride Investments Limited | Real estate | 2019 |
| CMA Solutions London Ltd | Other services | 2012 |
| Cmacleod Holdings Limited | Real estate | 2023 |
| Cmaniar Limited | Professional & scientific | 2008 |
| Cmbest Construction Ltd | Construction | 2018 |
| CMC Gold Recruitment Ltd | Professional & scientific | 2026 |
| CMD Domestic Building Ltd | Construction | 2020 |
| CME Painting & Decorating Ltd | Construction | 2024 |
| Cmhsr Ltd | Arts & recreation | 2025 |
| Cmihai Services Ltd | Construction | 2024 |
| CMK Entertainment Group Limited | Arts & recreation | 2019 |
| CMM Advisory Ltd | Professional & scientific | 2023 |
| Cmss Solutions Limited | Transport & logistics | 2019 |
| CMW Securities Limited | Administrative & support | 2004 |
| CN Supplies Limited | Wholesale & retail | 2024 |
| CN1 Ltd | Construction | 2018 |
| CNA Estates and Developments Ltd | Real estate | 2024 |
| CND Tutors Ltd | Education | 2024 |
| Cndr Limited | Professional & scientific | 2025 |
| CNL Heating Ltd | Construction | 2022 |
| CNM Homes Ltd | Real estate | 2021 |
| CNM Property Services Ltd | Agriculture & fishing | 1996 |
| CNS Limited | Professional & scientific | 2016 |
| CNT Construction Ltd | Construction | 2018 |
| Co Assist Services Limited | Other services | 1994 |
| Co-Living Supported Developments Limited | Construction | 2022 |
| CO2 Bar and Events Ltd | Hospitality | 2021 |
| Coach NIC Ltd | Health & social care | 2023 |
| Coaching 4 U Ltd | Administrative & support | 2020 |
| Coachworks Lodge Freehold Company Limited | Real estate | 2019 |
| Coaja Construct Ltd | Manufacturing | 2022 |
| Coanectasin Ltd | Other services | 2025 |
| COAST2COAST Removals and Storage Limited | Transport & logistics | 2022 |
| Coastal Consultancy Services Ltd | Hospitality | 2020 |
| Coastalbase Limited | Real estate | 2011 |
| Coastlands Architecture Ltd | Professional & scientific | 2015 |
| Cobalt Financial Holdings Limited | Financial services | 2021 |
| Cobalt Financial Ltd | Administrative & support | 2013 |
| Cobb Holdings Limited | Health & social care | 2015 |
| Cobden Assets Management Ltd | Real estate | 2022 |
| Coberg Services Limited | Health & social care | 2024 |
| Cobest Tiling Ltd | Construction | 2023 |
| Cobh Investments Ltd | Financial services | 2017 |
| Cobh Property Developments Ltd | Construction | 2019 |
| Cobra Automotives Limited | Wholesale & retail | 2007 |
| Cochno Subsea Ltd | Professional & scientific | 2014 |