| CNN Electrical Ltd | Construction | 2020 |
| CNS Estates Ltd | Real estate | 2023 |
| CNS Software Ltd | Professional & scientific | 2015 |
| Coastal City Roofing Ltd | Construction | 2026 |
| Coastal Harmony Ltd | Hospitality | 2020 |
| Cobweb Media Limited | Professional & scientific | 2011 |
| Code Craftsman Services Limited | Information & communication | 2015 |
| Codex Consulting Hampshire Ltd | Information & communication | 2014 |
| Coglan Airconditioning Services Limited | Energy | 2002 |
| Cohalasu Limited | Information & communication | 2025 |
| Cold Chilli Carpentry Limited | Construction | 2019 |
| Coldsmiths Limited | Manufacturing | 2023 |
| Cole Armitage Limited | Professional & scientific | 2014 |
| Colebrook Construction Limited | Construction | 2023 |
| Colella Interiors Limited | Construction | 2017 |
| Colenzo Properties Limited | Real estate | 2021 |
| Coles Building Solutions Limited | Construction | 2025 |
| Collaborative Analysis Limited | Information & communication | 2012 |
| College Sports America Limited | Arts & recreation | 2017 |
| Collins Residential Ltd | Real estate | 2018 |
| Colour Inc Limited | Manufacturing | 2002 |
| Columnsoft Limited | Information & communication | 2006 |
| COM4T Ltd | Wholesale & retail | 2014 |
| Cometa Group Ltd | Professional & scientific | 2026 |
| Comfort Building Services Ltd. | Construction | 1995 |
| Comfort Limited | Professional & scientific | 1997 |
| Comfort Zone Properties Limited | Construction | 2020 |
| Comfybargains Ltd | Wholesale & retail | 2025 |
| Commercial Buildings Technical Solutions Limited | Construction | 2007 |
| Commsplus Limited | Information & communication | 1988 |
| Community Herbal AID CIC | Health & social care | 2023 |
| Community Sport 4 Education Limited | Arts & recreation | 2011 |
| Community Technical Support Ltd | Information & communication | 2009 |
| Compact High Speed Ltd | Manufacturing | 2023 |
| Complementary Advisory Solutions Ltd | Professional & scientific | 2023 |
| Complete Building Services Ltd | Extraterritorial | 2005 |
| Complete Contract Maintenance Services Limited | Construction | 2014 |
| Complete Copywriting Limited | Professional & scientific | 2014 |
| Complete Hospitality Services Limited | Hospitality | 2019 |
| Complete Lighting Services Limited | Manufacturing | 1996 |
| Complete Performance Ltd | Arts & recreation | 2015 |
| Complete Temperature Control Ltd | Energy | 2012 |
| Compound Creative Limited | Professional & scientific | 2017 |
| Compounding Content Ltd | Information & communication | 2025 |
| Comprehensive Therapies Limited | Health & social care | 2009 |
| Comptech Solutions Ltd | Manufacturing | 2024 |
| Compute Carbon Limited | Information & communication | 2014 |
| Computer Requisites Limited | Information & communication | 1990 |
| Computer Trade Limited | Wholesale & retail | 2006 |
| Computherapy Limited | Information & communication | 2021 |
| Comset Cleaning Services Ltd | Administrative & support | 2025 |
| Comtext Computer & Network Consultants Limited | Professional & scientific | 1989 |
| Concept Electrical and Maintenance Limited | Construction | 2004 |
| Concept Energy Consulting Ltd | Professional & scientific | 2008 |
| Concept Energy Solutions Ltd | Professional & scientific | 2008 |
| Concept Energy Technologies Ltd | Other services | 2008 |
| Concept Orange Ltd | Professional & scientific | 2021 |
| Concerto Projects Limited | Professional & scientific | 2012 |
| Concise Communications Limited | Professional & scientific | 2014 |
| Concordia Psychological Services Ltd | Health & social care | 2018 |
| Condition Online Remote Monitoring Systems Limited | Other services | 2008 |
| Connect Computer Consultants Limited | Information & communication | 1994 |
| CONNECT999 Limited | Transport & logistics | 2024 |
| Connectegrity Ltd | Information & communication | 2009 |
| Connective Chiropractic Limited | Health & social care | 2017 |
| Consilium Road Partners Limited | Information & communication | 2018 |
| Consortium Energy Technologies Limited | Information & communication | 2026 |
| Constrabase Ltd | Construction | 2023 |
| Construction Industry Buying Limited | Construction | 2006 |
| Consulting Basingstoke Limited | Hospitality | 2025 |
| Consulting Engineering Solutions Limited | Professional & scientific | 2007 |
| Continental Asset Management Limited | Professional & scientific | 2017 |
| Continental Bake Ltd | Wholesale & retail | 2024 |
| Continuum Care Limited | Health & social care | 2025 |
| Contractors Marketing Services Ltd | Professional & scientific | 2011 |
| Control Pest UK Ltd | Administrative & support | 2012 |
| Control Room Finance Limited | Professional & scientific | 2020 |
| Controllabs Ltd | Information & communication | 2024 |
| Converse Telecom Limited | Information & communication | 2002 |
| Cook & Jacobs Electrical Ltd | Construction | 2014 |
| Cool Breeze Telemarketing & Marketing Limited | Administrative & support | 2024 |
| Cool Cable Ltd | Manufacturing | 2014 |
| Cool Cats Driving School Ltd | Education | 2021 |
| Cool Crave Limited | Hospitality | 2025 |
| Cool Smiles Ltd | Health & social care | 2021 |
| Coomber Rich Limited | Professional & scientific | 2011 |
| Cooper Payments Consultancy Ltd | Information & communication | 2026 |
| Coppice ROW Trading Limited | Wholesale & retail | 2018 |
| Copse Holdings Ltd | Financial services | 2026 |
| Corbiere House Residents Management Company Ltd | Administrative & support | 2016 |
| Cordebene Ltd | Professional & scientific | 2021 |
| Cordery's Meadow Company Ltd | Real estate | 2020 |
| Core Therapies Diet Centre Ltd | Hospitality | 2019 |
| Core Therapies Ltd | Other services | 2017 |
| Corgi Technical EOT Limited | Administrative & support | 2022 |
| Corgi Technical Services Group Limited | Financial services | 2022 |
| Corgi Technical Services Limited | Professional & scientific | 2009 |
| Cornerstone Learning CIC | Education | 2024 |
| Cornfield Advisory Ltd | Professional & scientific | 2018 |
| Cornford House Limited | Health & social care | 2001 |