| Clairity Analytics Limited | Professional & scientific | 2025 |
| Clan Middleton Property Holdings Ltd | Real estate | 2025 |
| Clare Webber Counselling Ltd | Health & social care | 2024 |
| Clarity and Confidence Ltd | Other services | 2021 |
| Clarity Site Services Ltd | Water & waste | 2026 |
| Classic Folios Limited | Information & communication | 2002 |
| Classic Golf International Holdings Ltd | Financial services | 2018 |
| Classic Golf International Ltd. | Administrative & support | 1993 |
| Clean Sweep South Coast Limited | Administrative & support | 2018 |
| Clean Voice Media Ltd | Information & communication | 2022 |
| Clean Windows & Gutters Limited | Administrative & support | 2014 |
| Clear CUT Property Reporting Ltd | Administrative & support | 2018 |
| Clear Electrical Services Limited | Construction | 2016 |
| Clear Vision Glass Limited | Manufacturing | 2020 |
| Clearall Glass Repairs Ltd | Construction | 2013 |
| Clearline Communications (Winchester) Ltd | Administrative & support | 2002 |
| Clearpoint Legal Limited | Professional & scientific | 2013 |
| Clenz Limited | Administrative & support | 2023 |
| Clerion Ltd | Professional & scientific | 2025 |
| Clevercat Digital Media Limited | Information & communication | 2014 |
| Cleverly Wrapped Ltd | Wholesale & retail | 2013 |
| Cliff LEE FS Ltd | Financial services | 2015 |
| Cliffe-Roberts Limited | Professional & scientific | 1995 |
| Cliffway Limited | Real estate | 1963 |
| Clint Kent Catering Ltd | Hospitality | 2024 |
| Clive Barford Limited | Administrative & support | 1986 |
| Clive Collins Electrical Limited | Construction | 2003 |
| Cloudcom Technologies Ltd | Information & communication | 2022 |
| Clouds Nest Solutions Ltd | Information & communication | 2024 |
| Club Racing UK Ltd | Other services | 2023 |
| Clutch Digital Marketing Ltd | Professional & scientific | 2026 |
| CM Plumbing & Bathroom Installations Ltd | Construction | 2025 |
| Cmabb Limited | Health & social care | 2016 |
| CMC Design (Southern) Ltd | Professional & scientific | 2012 |
| Cmep Group Ltd | Construction | 2016 |
| Cmlemergency Ltd | Construction | 2025 |
| Cmrs Property Services Ltd | Administrative & support | 2022 |
| CMS Estates & Holdings Ltd | Real estate | 2022 |
| CMT Plumbing & Heating Ltd | Construction | 2025 |
| Co-Communications Limited | Construction | 1990 |
| Coach & Horses (Salisbury) Limited | Hospitality | 2023 |
| COACH4U Limited | Education | 2018 |
| Coaching at Proco Ltd | Administrative & support | 2021 |
| Coast and Bloom Ltd | Professional & scientific | 2021 |
| Coast Hotels and Leisure Limited | Hospitality | 2004 |
| Coastal & Waterways Ltd | Administrative & support | 2004 |
| Coastline Home Improvements IOW Limited | Extraterritorial | 2018 |
| Coasttocoastfoods Limited | Hospitality | 2023 |
| Cobra Installations Limited | Wholesale & retail | 1993 |
| Code 9 Facilities Ltd | Professional & scientific | 2013 |
| Code 9 Fire Ltd | Professional & scientific | 2013 |
| Code 9 Group Ltd | Administrative & support | 2016 |
| Code 9 Medical Ltd | Health & social care | 2013 |
| Code 9 Risk Management Ltd | Professional & scientific | 2016 |
| Code Advisory Ltd | Professional & scientific | 2023 |
| Codigana Ltd | Information & communication | 2020 |
| COE & Jamison Ltd | Construction | 2020 |
| Coffee MAN Repairs Limited | Manufacturing | 2017 |
| Coffeebrains Limited | Information & communication | 2016 |
| COG Coder Limited | Information & communication | 2013 |
| Cold Air Limited | Construction | 2003 |
| Colin Leech Limited | Financial services | 2021 |
| Colin Sharpe Limited | Construction | 2005 |
| Collecting Seashells Limited | Wholesale & retail | 2020 |
| College of Security Ltd | Education | 2017 |
| Collier Investment Holdings Limited | Real estate | 2024 |
| Collier Projects Limited | Construction | 2014 |
| Collinge Corporate Support Limited | Professional & scientific | 2004 |
| Colmena Limited | Construction | 2016 |
| Colour Company (Southampton ) Limited | Manufacturing | 2002 |
| Colour Nails & Beauty Limited | Other services | 2024 |
| Colourspring Clinical Services Ltd | Professional & scientific | 2024 |
| Coman Build Ltd | Construction | 2016 |
| Combined Flooring EOT Limited | Professional & scientific | 2016 |
| Combined Flooring Services Limited | Construction | 1988 |
| Commerce Fulfilment Limited | Wholesale & retail | 2024 |
| Commercial Resolutions Ltd | Professional & scientific | 2008 |
| Commercial Roofline Services Ltd | Construction | 1998 |
| Committee on Publication Ethics | Professional & scientific | 2007 |
| Commonsense Innovations Ltd | Financial services | 2025 |
| Commstruct Services Limited | Information & communication | 2016 |
| Commtronix Limited | Administrative & support | 2008 |
| Communication Technical Services Limited | Manufacturing | 1965 |
| Como Diffusion Limited | Wholesale & retail | 2003 |
| Compare the Cloud Ltd | Administrative & support | 2011 |
| Compass UK Bidco Limited | Financial services | 2021 |
| Compass UK Holdco Limited | Financial services | 2021 |
| Compass UK Midco Limited | Financial services | 2021 |
| Compass UK Topco Limited | Financial services | 2020 |
| Compassionate Cuppa CIC | Education | 2020 |
| Complete Skin Solutions Ltd | Wholesale & retail | 2022 |
| Complete Your Collection Limited | Wholesale & retail | 2021 |
| Complex-Solutions Ltd | Construction | 2024 |
| Composide Limited | Information & communication | 2013 |
| Composite FEA Consulting Ltd | Professional & scientific | 2021 |
| Compton & Cross Plumbing & Heating Ltd | Construction | 2020 |
| Computerxplorers Limited | Information & communication | 2021 |
| Concannon Installations Ltd | Construction | 2019 |
| Concept Corporate Ltd | Wholesale & retail | 2014 |
| Concorde Insurance Brokers Limited | Financial services | 1995 |