| Cospace Group Stevenage NO25 Limited | Real estate | 2020 |
| Cospace Group TH Limited | Real estate | 2026 |
| Cosyhome Resources Limited | Wholesale & retail | 2025 |
| Cotech UK ICS Limited | Administrative & support | 2013 |
| Cottonfields Ltd | Health & social care | 2017 |
| Coughlan Enterprises Limited | Financial services | 2016 |
| Coughlan Management Ltd | Real estate | 2017 |
| Coughlan Property Ltd | Real estate | 2017 |
| Council of Ex-Muslims of Britain | Other services | 2012 |
| Countrywide Property Management Limited | Real estate | 1990 |
| County Castles Limited | Extraterritorial | 2003 |
| County Funerals Limited | Other services | 2017 |
| County Funerals of Letchworth Ltd | Other services | 2023 |
| County Holdings International Ltd | Financial services | 2024 |
| County Renovations Limited | Construction | 2022 |
| County Teachers Ltd | Administrative & support | 2002 |
| Courage D Caring Services Ltd | Health & social care | 2021 |
| Courtyard Residents Limited | Other services | 2004 |
| Cover for YOU Services Ltd | Information & communication | 2018 |
| Covered Group Ltd | Other services | 2024 |
| COX Retrofit Solutions Limited | Construction | 2024 |
| Coxall Inns Ltd | Hospitality | 2026 |
| Cp&D Ltd | Other services | 2022 |
| CPC Bathrooms Ltd | Wholesale & retail | 2019 |
| CR and Sons Ltd | Construction | 2020 |
| Craftstone Fireplaces Limited | Wholesale & retail | 2003 |
| Craig COE Ltd | Construction | 2024 |
| Crane Builders Limited | Construction | 2012 |
| Craoibhe-Caorainn Ltd | Information & communication | 2025 |
| Crawford Oakley Creatives Ltd | Arts & recreation | 2024 |
| CRE878 Studio Ltd | Arts & recreation | 2025 |
| Create PCS Ltd | Manufacturing | 2020 |
| Creating Pathfinders Ltd | Education | 2025 |
| Creative Space Construction Ltd | Construction | 2021 |
| Creatown Graphic Design Limited | Information & communication | 2020 |
| Credit for Construction Ltd | Construction | 2020 |
| Creer Group Ltd | Administrative & support | 2023 |
| Crestina Ltd | Health & social care | 2017 |
| Crestpointe Capital Limited | Real estate | 2025 |
| Crewbus Ltd | Information & communication | 2019 |
| Crewys Estates Ltd | Real estate | 2020 |
| Cricklewood Timber and Building Supplies Limited | Extraterritorial | 2025 |
| Crimx Construction Limited | Construction | 2023 |
| Crispins Folly Management Company Limited | Households | 2006 |
| Cristal Power Limited | Other services | 2018 |
| Cristian H Services Ltd | Other services | 2019 |
| Cristian Ltd. | Construction | 2014 |
| Cristina&Andrei Transport Ltd | Transport & logistics | 2026 |
| Crocelectrical Ltd | Construction | 2025 |
| Croft Maritime Limited | Professional & scientific | 2016 |
| Crom Properties Ltd | Real estate | 2020 |
| Cronos Developments Limited | Construction | 2017 |
| Cronos Group Limited | Real estate | 2016 |
| Crosscut Productions Ltd | Administrative & support | 2003 |
| Crossing Streams Ltd | Administrative & support | 2007 |
| Crowded PUB Company Limited | Hospitality | 2021 |
| Crowland & Wolf Holdings LLP | | 2022 |
| Crowland & Wolf Ltd | Real estate | 2022 |
| Crown & Glory Group Ltd | Education | 2020 |
| Crown Contractors Ltd | Administrative & support | 2016 |
| Crown Food Store Ltd | Wholesale & retail | 2023 |
| Crown Volt Engineering Ltd | Professional & scientific | 2024 |
| Crownthrone International Limited | Professional & scientific | 2012 |
| Crownthrone Pet Foods Ltd | Manufacturing | 2015 |
| Croydon Films Limited | Information & communication | 2010 |
| Crucial Response Ltd | Administrative & support | 2025 |
| Crumpled Limited | Arts & recreation | 2008 |
| Crusoe Consulting Ltd. | Information & communication | 2019 |
| Crutchfield Limited | Financial services | 2024 |
| Cruz Microsystems Limited | Other services | 1979 |
| Cruz’S Properties Limited | Real estate | 2026 |
| Cryoport UK Limited | Transport & logistics | 2017 |
| Crystal Clean 2026 Limited | Hospitality | 2026 |
| Crystal Clean Herfordshire Ltd | Administrative & support | 2025 |
| Crystal Clear Project Management Ltd | Professional & scientific | 2023 |
| CS Health Care Ltd | Health & social care | 2020 |
| CS Marketing Solutions Limited | Professional & scientific | 2024 |
| CS Tuning Ltd | Wholesale & retail | 2023 |
| Csej Limited | Financial services | 2009 |
| CSL Surveys (Stevenage) Limited | Professional & scientific | 2003 |
| CSL Surveys Limited | Professional & scientific | 1992 |
| CSP Consultancy Ltd | Information & communication | 2026 |
| CSR Building Limited | Construction | 2010 |
| CSR Cleaning Services Ltd | Administrative & support | 2025 |
| CT Commercial Vehicles Ltd | Wholesale & retail | 2023 |
| CT Physio Ltd | Health & social care | 2025 |
| Ctbs Group Limited | Wholesale & retail | 1992 |
| CTH Rail Ltd | Transport & logistics | 2023 |
| CTK Medical Associates Limited | Professional & scientific | 2007 |
| CTM Plastering Limited | Construction | 2023 |
| Cubelogix Limited | Other services | 2006 |
| CUBIC8 Limited | Information & communication | 2005 |
| CUBIC8 Networks Limited | Professional & scientific | 2015 |
| Culrose Court Residents Limited | Households | 2003 |
| CUP of Cosy Limited | Hospitality | 2024 |
| Cupican Ltd | Financial services | 2026 |
| Curious Butterflies Nursery Ltd | Health & social care | 2025 |
| Curly Tails Canine Rehab Ltd | Professional & scientific | 2020 |
| Currant Carpets Ltd | Other services | 2021 |
| Current Flex Ltd | Information & communication | 2025 |