| Court Harvest Homes Limited | Construction | 1984 |
| Court Homes Construction (Hitchin) Ltd | Construction | 2018 |
| Court Homes Developments Ltd | Construction | 2018 |
| Court Homes in Partnership Ltd | Construction | 2018 |
| Cousins Carpets Ltd | Wholesale & retail | 2022 |
| Cozycorner Spaces Limited | Hospitality | 2024 |
| CP Harcourt Invesments Limited | Real estate | 2023 |
| CPB Media Ltd | Information & communication | 2021 |
| CPM Playgrounds Limited | Manufacturing | 2009 |
| Crabtree and Co Advisory Ltd | Professional & scientific | 2026 |
| Crafted Companions Limited | Hospitality | 2024 |
| Craig Tribe Child and Educational Psychology Limited | Professional & scientific | 2017 |
| Cranbourne Financial Limited | Financial services | 2006 |
| Crash Care Centre (Hitchin) Limited | Wholesale & retail | 2017 |
| Cravequest Group Limited | Hospitality | 2025 |
| Cravequest Private Ltd | Hospitality | 2026 |
| Crawley Maintenance Ltd | Administrative & support | 2021 |
| Crazy 4 Kids Ltd | Education | 2008 |
| CRD Property Investments Limited | Real estate | 2025 |
| Create Flow Limited | Education | 2020 |
| Create Network Limited | Education | 2008 |
| Create Pressing Ltd | Information & communication | 2017 |
| Creatico Limited | Wholesale & retail | 2005 |
| Creating Futures Together Ltd | Education | 2024 |
| Creation Entertainment Media Ltd | Information & communication | 2020 |
| Creation Publishing Ltd | Information & communication | 2019 |
| Creative Carpentry & Kitchens Limited | Construction | 2015 |
| Creative Construction Solutions Ltd | Construction | 2018 |
| Creative Meld Limited | Professional & scientific | 2011 |
| Creative Minds CIC | Education | 2019 |
| Creative Teachers Recruitment Ltd | Administrative & support | 2024 |
| Creative Theatre Academy Limited | Administrative & support | 2017 |
| Creative Unblock Ltd | Professional & scientific | 2019 |
| Creme Events Limited | Administrative & support | 2024 |
| Crescent Cleaning Services Limited | Administrative & support | 2020 |
| Crestel Projects Ltd | Construction | 2011 |
| Cripps Commercial Cleaning Limited | Construction | 2023 |
| Cris Beswick Consulting Ltd | Professional & scientific | 2008 |
| Critical Thinking UK Limited | Education | 2018 |
| CRN Contract Maintenance Ltd | Administrative & support | 2009 |
| CRN Ltd | Administrative & support | 2007 |
| CRN Properties Ltd | Real estate | 2022 |
| Croe Architects ARB Limited | Professional & scientific | 2022 |
| Croe Architects LLP | | 2016 |
| Cromwell Cars Ltd | Wholesale & retail | 2022 |
| Cromwell Court Management (Letchworth) Limited | Households | 1987 |
| Crossover Blendery Limited | Manufacturing | 2019 |
| Crossroads Caring for Life Ltd | Health & social care | 2007 |
| Crossrow Ltd | Wholesale & retail | 2024 |
| Crowhurst Estates Limited | Real estate | 2026 |
| Crown Life Coaching Ltd | Other services | 2024 |
| Crown M & E Ltd | Manufacturing | 2014 |
| Crown Topiary Limited | Wholesale & retail | 2018 |
| Crucial Plumbing and Heating Ltd | Construction | 2019 |
| Crumbelieveable UK Ltd | Wholesale & retail | 2025 |
| Cryo Gaming Ltd | Wholesale & retail | 2018 |
| Cryptex Security (UK) LLP | | 2013 |
| Cryptex Security Services Ltd | Administrative & support | 2008 |
| Crystal Lake Ltd | Professional & scientific | 2008 |
| Crystallised Communications Limited | Professional & scientific | 2022 |
| CS Build Group Ltd | Construction | 2023 |
| CS Multifloor Ltd | Construction | 2020 |
| CS3 Clinical Limited | Administrative & support | 2022 |
| CS3C Cleaning Ltd | Administrative & support | 2025 |
| CS3C Education Ltd | Administrative & support | 2016 |
| CS3C Health Ltd | Administrative & support | 2015 |
| CS3C Hygiene Ltd | Administrative & support | 2016 |
| CS3C Ltd | Administrative & support | 2014 |
| CS3C Medical Ltd | Administrative & support | 2015 |
| CSP Homes Ltd | Extraterritorial | 2020 |
| CT Hilltop Limited | Real estate | 2024 |
| CTK Logistics Limited | Transport & logistics | 2025 |
| CTK Support Services Limited | Administrative & support | 2026 |
| CTS (UK) Exports Limited | Wholesale & retail | 2003 |
| Cube Block Management UK Limited | Real estate | 2024 |
| Cubic Cycle Ltd | Professional & scientific | 2012 |
| Cuneiform Accountancy Limited | Professional & scientific | 2021 |
| Curcic Construction Services Limited | Professional & scientific | 2019 |
| Current Solutions Electrical Limited | Manufacturing | 2008 |
| Curtis and Hind Limited | Real estate | 2022 |
| Curtis Medical Investments Limited | Real estate | 1995 |
| Custom Consoles Limited | Manufacturing | 1996 |
| Custom Gardens Design & Landscaping Ltd | Administrative & support | 2022 |
| Cutloose Utilities Limited | Construction | 2025 |
| Cutting Edge Developments (UK) Ltd | Extraterritorial | 2014 |
| Cwagencies London Ltd | Wholesale & retail | 2022 |
| CWB Carpentry & Construction Ltd | Manufacturing | 2024 |
| CWF Refurbishments Limited | Construction | 2014 |
| Cyberdrive Ltd | Real estate | 1995 |
| Cybertrek Limited | Information & communication | 1997 |
| Cycledealia Limited | Manufacturing | 1999 |
| Cyclo-Ssage Equine (UK) Limited | Wholesale & retail | 2011 |
| Cyntra Reactive Ltd | Administrative & support | 2025 |
| Czech Medical Ltd | Health & social care | 2019 |
| D & G Appliance Repairs and Servicing Limited | Other services | 2026 |
| D & J Lettings and Property Management Limited | Real estate | 2007 |
| D and E Accountancy Ltd | Professional & scientific | 2002 |
| D J B Carpentry Limited | Construction | 1997 |
| D R Design Graphics Limited | Professional & scientific | 2010 |
| D Rathborne Limited | Real estate | 2016 |