| Cirencester Computer Centre Limited | Information & communication | 1984 |
| Cirencester Elite Cheer & Dance Academy Ltd | Education | 2025 |
| Cirencester Pizza & Chicken HUT Ltd | Hospitality | 2024 |
| Cirencester Sushi Ltd | Hospitality | 2024 |
| Cirou Ltd | Real estate | 2020 |
| Citifaith Church | Other services | 2004 |
| Citrus Design & Print Limited | Manufacturing | 2006 |
| Citruz Real Estate Investment LP | | 2014 |
| City Broadband Limited | Extraterritorial | 2001 |
| City of London HR Services Limited | Administrative & support | 2014 |
| City Signs & Design Ltd | Manufacturing | 2014 |
| Civicsoft Ltd | Information & communication | 2025 |
| CJ O'Connell Ltd | Professional & scientific | 2026 |
| CJA International PTE Ltd | Wholesale & retail | 2009 |
| CJD Accountancy Limited | Professional & scientific | 2011 |
| CJD Logistics Swindon Ltd | Transport & logistics | 2024 |
| CJG Electrical Services Limited | Construction | 2019 |
| CJW Electrical Services Ltd | Construction | 2021 |
| CK Elite Services Ltd | Transport & logistics | 2025 |
| CK Elite Trading Ltd | Wholesale & retail | 2025 |
| CK Enterprises Limited | Administrative & support | 2007 |
| CKH Design Ltd | Professional & scientific | 2021 |
| CKM - Plumbing Ltd | Construction | 2025 |
| CKM Partners Ltd | Financial services | 2025 |
| Cksk Consulting Ltd. | Professional & scientific | 2013 |
| CL Cleanz Ltd | Administrative & support | 2026 |
| CL Couriers Ltd | Transport & logistics | 2024 |
| CL Development Solutions Ltd | Construction | 2020 |
| CL Thomas Ltd | Manufacturing | 2023 |
| Claim My Finance Limited | Professional & scientific | 2025 |
| Claire Mccormick Consulting Ltd | Professional & scientific | 2009 |
| Claire White LLP | | 2012 |
| Claremont Court Management (Swindon) Limited | Hospitality | 1972 |
| Clarissa Property Limited | Real estate | 2020 |
| Claritum Limited | Information & communication | 1999 |
| Clarity Assessment Specialists Environmental Limited | Professional & scientific | 2009 |
| Clarity Software Solutions Limited | Information & communication | 2014 |
| Clarity Training Solutions Ltd | Professional & scientific | 2025 |
| Clarius Media Limited | Information & communication | 2026 |
| Clark Project Management Limited | Professional & scientific | 2008 |
| Clarke & Dean Properties Ltd | Real estate | 2018 |
| Clarus Motorpark Body Shops Ltd | Wholesale & retail | 2019 |
| Clarus Motorpark Bristol Ltd | Wholesale & retail | 2019 |
| Class 1 Driving School Ltd | Education | 2013 |
| Classic Drives & Patios Ltd | Administrative & support | 2019 |
| Claudie's Car Cleaning Ltd | Administrative & support | 2022 |
| Claudio Designs Ltd | Construction | 2021 |
| Claycourt Limited | Extraterritorial | 2016 |
| Clayhill Solar Limited | Energy | 2013 |
| CLB & Co. Ltd | Information & communication | 2025 |
| Clean Eco Ltd | Administrative & support | 2022 |
| Clean Slate Swindon Ltd | Administrative & support | 2021 |
| Clean Sweeping Ltd | Other services | 2012 |
| Cleanlink Software Limited | Information & communication | 2005 |
| Clear Blue Consulting Ltd | Administrative & support | 2021 |
| Clear Incor Limited | Professional & scientific | 2022 |
| Clearsite Solutions Ltd | Construction | 2010 |
| Clearview Internet Solutions Limited | Information & communication | 2012 |
| Clearvu Financial Solutions Limited | Professional & scientific | 2016 |
| Clearwater Commercial Investments & Developments Limited | Construction | 2024 |
| Clearwater Commercial Ventures Limited | Construction | 2024 |
| Clearwater Property Ventures Limited | Construction | 2024 |
| Clearwater Ventures Limited | Professional & scientific | 2024 |
| Cleenie Ltd | Information & communication | 2025 |
| Cleerex Ltd | Construction | 2018 |
| Clemency Rittner Soft Furnishings Limited | Manufacturing | 2000 |
| Clement Enterprises Limited | Health & social care | 2018 |
| Clements Building Contractors Limited | Construction | 2006 |
| Cletus Vehicles Ltd | Wholesale & retail | 2023 |
| Clever Art Limited | Information & communication | 2003 |
| Click & Clean Cirencester Ltd | Administrative & support | 2018 |
| Click & Move (Swindon) Ltd | Transport & logistics | 2019 |
| Click & Store (Swindon) Ltd | Transport & logistics | 2024 |
| Click a Brick Toys Limited | Wholesale & retail | 2015 |
| Click to Switch Ltd | Energy | 2022 |
| Client Ascend Ltd | Administrative & support | 2025 |
| Client Rhino Ltd | Professional & scientific | 2020 |
| Clifford Wealth Management Limited | Professional & scientific | 2020 |
| Clinch & Foley Limited | Construction | 2011 |
| Clinethos Ltd | Professional & scientific | 2026 |
| Clinical Staffing Limited | Health & social care | 2024 |
| Clipsize Ltd. | Information & communication | 2018 |
| Cliste Pharma Solutions Ltd | Professional & scientific | 2018 |
| Clive Elliott’S Martial Arts Academies LLP | | 2024 |
| Cljr Ltd | Wholesale & retail | 2024 |
| Clobdata Solutions Limited | Information & communication | 2015 |
| Clockwork Conferences Limited | Administrative & support | 2006 |
| Closetq.Ai Limited | Arts & recreation | 2026 |
| Closewatch Limited | Administrative & support | 2024 |
| Cloud Aiops Consulting Ltd | Information & communication | 2015 |
| Cloud Cottages Ltd | Hospitality | 2018 |
| Cloud Monitoring Services Ltd | Information & communication | 2022 |
| Cloud Nine Hair and Beauty Limited | Other services | 2014 |
| Cloud Spartan Limited | Information & communication | 2025 |
| CLOUD3 Solutions Ltd | Information & communication | 2022 |
| Cloudai OPS Ltd | Information & communication | 2025 |
| Cloudbourne Consulting Ltd | Information & communication | 2026 |
| Cloudbourne Ltd | Information & communication | 2024 |
| Cloudbridge Capital Limited | Information & communication | 2025 |
| Cloudship Consulting Ltd | Information & communication | 2016 |