| Cloud 9 Spa Ltd | Health & social care | 2014 |
| Clowsley Industries Ltd. | Financial services | 2016 |
| CM Engineering (Sales) Limited | Wholesale & retail | 2015 |
| CMB Automotive Group Limited | Information & communication | 2025 |
| CMB Automotive Marketing Limited | Information & communication | 2010 |
| CMH Electrical Engineers Ltd | Construction | 2016 |
| CMK Shotokan Karate BEO Limited | Education | 2012 |
| CMS Contractor Limited | Information & communication | 2012 |
| CMS Software Limited | Professional & scientific | 2019 |
| Co Photography and Design Ltd | Professional & scientific | 2017 |
| CO2PEC Ltd | Construction | 2019 |
| Coact Limited | Professional & scientific | 2018 |
| Coastal Green Landscapers Ltd | Administrative & support | 2025 |
| Cobalt 30 Limited | Construction | 2018 |
| Code Construction Ltd | Construction | 2017 |
| Cogeim Design Ltd | Professional & scientific | 2018 |
| Cogent Action Limited | Professional & scientific | 2024 |
| Cole Consultancy MK Ltd | Professional & scientific | 2018 |
| Coleman and Jones Limited | Agriculture & fishing | 2014 |
| Colmar Investments Limited | Professional & scientific | 1999 |
| Colrei Ltd | Hospitality | 2024 |
| Columba Leasing Limited | Real estate | 1983 |
| Commercial Fencing Solutions Limited | Construction | 2021 |
| Community Health-Works UK CIC | Health & social care | 2020 |
| Compact Camper Company Limited | Construction | 2023 |
| Compare the Tools Limited | Wholesale & retail | 2018 |
| Compassionate Support Ltd | Health & social care | 2025 |
| Compatech U.K. Ltd | Wholesale & retail | 2012 |
| Competition Supplies Limited | Wholesale & retail | 2008 |
| Complete Ground Management Limited | Real estate | 2002 |
| Concept Engineering Solutions Ltd | Professional & scientific | 2016 |
| Concique Ltd | Professional & scientific | 2007 |
| Conduit Resourcing Limited | Extraterritorial | 2012 |
| Congewai Investments Limited | Financial services | 2023 |
| Consolidated Rail Ltd | Manufacturing | 2019 |
| Construction Management Software Limited | Information & communication | 2002 |
| Cook PM Limited | Real estate | 2018 |
| Cookr Ltd | Information & communication | 2025 |
| Cool Name Limited | Financial services | 2025 |
| Cooper Banks Mackenzie Limited | Extraterritorial | 2008 |
| Coopers Consultancy Limited | Professional & scientific | 2010 |
| Copper Tree Holdings Ltd | Financial services | 2020 |
| Copper Tree Investments Ltd | Financial services | 2020 |
| Coppertree Developments Limited | Construction | 2019 |
| Corbyco Limited | Real estate | 2011 |
| Core Logistical Solutions Limited | Transport & logistics | 2024 |
| Cornerstone FD Ltd | Professional & scientific | 2019 |
| Corporate Development Resources Limited | Extraterritorial | 2017 |
| Corran Group Limited | Financial services | 2023 |
| Corrigan Consulting Ltd | Professional & scientific | 2022 |
| Covenant Enterprises Limited | Wholesale & retail | 2023 |
| CPG Accommodation Ltd | Real estate | 2021 |
| Craft Insight Limited | Professional & scientific | 2013 |
| Crafti's Holdings Ltd | Financial services | 2018 |
| Crafti's Ltd | Other services | 2007 |
| Cranfield Helicopter Charter Ltd | Transport & logistics | 2015 |
| Crantock Estates Ltd | Real estate | 2016 |
| Creacion Design Limited | Professional & scientific | 2014 |
| Createnext Ltd | Information & communication | 2025 |
| Creative Brands UK Limited | Professional & scientific | 2009 |
| Creative CAM Ltd | Professional & scientific | 2023 |
| Creative Magic Studio Ltd | Administrative & support | 2008 |
| Creative Waste Solutions Ltd | Water & waste | 2016 |
| Creighton House Limited | Administrative & support | 2010 |
| Creo Fitness Limited | Arts & recreation | 2015 |
| Cressyn Group Ltd | Wholesale & retail | 2025 |
| Crick Evolve Ltd | Construction | 2018 |
| CRJ Media Limited | Information & communication | 2017 |
| Croft Stores Limited | Wholesale & retail | 2015 |
| Crosswir Limited | Professional & scientific | 2019 |
| Croughton Renewable Resources Centre Limited | Water & waste | 2007 |
| Cryptoware Ltd | Wholesale & retail | 2023 |
| CS Construct Limited | Construction | 2013 |
| CSG Financial Limited | Financial services | 2025 |
| Cyber Defence Solutions Group Limited | Financial services | 2014 |
| Cymco Ltd | Manufacturing | 2020 |
| D & C Consultancy Ltd | Other services | 2020 |
| D & S Properties and Leisure Limited | Real estate | 1988 |
| D V Blinds Limited | Manufacturing | 2003 |
| D&D Energy Ltd | Professional & scientific | 2024 |
| D&G Procurement Services Ltd | Professional & scientific | 2026 |
| D&S Carpentry Ltd | Construction | 2017 |
| D.J. Smith Bookkeeping Ltd | Professional & scientific | 2007 |
| D3 Design Associates Ltd | Professional & scientific | 2010 |
| D3 Design Ltd | Administrative & support | 2008 |
| D3 Group Associates Ltd | Financial services | 2015 |
| Dadford & Stowe Limited | Wholesale & retail | 2017 |
| DAF Enterprises Limited | Wholesale & retail | 2010 |
| Dale Landscaping Services Ltd | Administrative & support | 2008 |
| Damah Care Ltd | Health & social care | 2021 |
| Damsel in Shining Armour Ltd | Extraterritorial | 2020 |
| Danda Grill Limited | Hospitality | 2020 |
| Dandair Consulting Limited | Professional & scientific | 2015 |
| Danecca Asset Management Limited | Administrative & support | 2023 |
| Danecca Group Limited | Financial services | 2023 |
| Danecca Limited | Professional & scientific | 2012 |
| Danecca Systems Limited | Manufacturing | 2023 |
| Dapa Property Ltd | Construction | 2025 |
| Daring Media Ltd | Information & communication | 2026 |
| Darwin ROE Investments Limited | Financial services | 2021 |