| Commercial Brake Services Ltd | Wholesale & retail | 2002 |
| Commercial Building Interiors Ltd. | Construction | 1997 |
| Commercial by JLO Ltd | Construction | 2025 |
| Commercial Projects Limited | Real estate | 2000 |
| Commercial Retail Limited | Wholesale & retail | 2026 |
| Commercial Talent Partners Ltd | Administrative & support | 2025 |
| Commodity Agent Limited | Professional & scientific | 2023 |
| Commodity Trading Desk UK Ltd | Manufacturing | 2023 |
| Communications & Change Management Consultancy Limited | Professional & scientific | 2016 |
| Community Cogs Limited | Hospitality | 2012 |
| Community Health and Eyecare (Holdings) Limited | Financial services | 2018 |
| Community Health and Eyecare Limited | Health & social care | 2010 |
| Community Help Africa & UK CIC | Education | 2012 |
| Community Life Choices Group Limited | Health & social care | 2017 |
| Community Life Choices Limited | Health & social care | 2015 |
| Community Science C.I.C. | Administrative & support | 2010 |
| Community Sport Ltd | Professional & scientific | 2003 |
| Compact Grounds Maintenance Limited | Administrative & support | 2002 |
| Companies 4 Sale Ltd | Other services | 2021 |
| Companion Holdings Ltd | Real estate | 2025 |
| Companion Homecare Ltd | Administrative & support | 2019 |
| Company Brain Limited | Information & communication | 2026 |
| Company Formations Worldwide.Com Ltd | Administrative & support | 2010 |
| Compare 365 Ltd | Financial services | 2003 |
| Compare Solutions Ltd | Administrative & support | 2004 |
| Compare the Brands Limited | Information & communication | 2014 |
| Compass Developments Limited | Construction | 1983 |
| Compass Fuel Oils Limited | Wholesale & retail | 2009 |
| Compass GAS Limited | Wholesale & retail | 2021 |
| Compass HSC Limited | Professional & scientific | 2002 |
| Compass Professional Development Limited | Information & communication | 2004 |
| Compassionate Pathways Ltd | Health & social care | 2024 |
| Compassrose Ltd | Professional & scientific | 2021 |
| Compeller Limited | Information & communication | 2013 |
| Complete Bathrooms & Kitchens Limited | Construction | 2002 |
| Complete Building Interior Solutions Limited | Construction | 2022 |
| Complete Concierge Solutions Ltd | Administrative & support | 2023 |
| Complete Construction and Interiors Ltd | Construction | 2023 |
| Complete Contracting Group Ltd | Construction | 2022 |
| Complete Convey Limited | Professional & scientific | 2015 |
| Complete Decorating Fylde Limited | Construction | 2006 |
| Complete Demolition Ltd | Construction | 2023 |
| Complete Electrical and Property Solutions Limited | Construction | 2013 |
| Complete Properties Ltd | Real estate | 2020 |
| Complete Property Cleaning Solutions Limited | Households | 2014 |
| Complete Property Management Solutions Limited | Households | 2004 |
| Complete Property Security Solutions Ltd | Administrative & support | 2023 |
| Complete Security Civils Limited | Construction | 2024 |
| Complete Steel Services Ltd | Manufacturing | 2017 |
| Complete Umbrella Results Limited | Administrative & support | 2016 |
| Completions Contracting Ltd | Professional & scientific | 2018 |
| Comply Direct Limited | Extraterritorial | 2023 |
| Composite Timber Company Ltd | Wholesale & retail | 2023 |
| Compound Paraplanning Limited | Administrative & support | 2023 |
| Computech World Limited | Wholesale & retail | 2024 |
| Computer Engineering Consultants Limited | Information & communication | 2013 |
| Computer Smart Limited | Other services | 2003 |
| Computingdata Ltd | Information & communication | 2023 |
| Comspal Limited | Transport & logistics | 2014 |
| Concept Akeso Consultancy Ltd | Professional & scientific | 2024 |
| Concept Building Solutions Limited | Extraterritorial | 2002 |
| Concept Building Solutions UK Limited | Construction | 2003 |
| Concept Cleaning Services and Facilities Management Ltd | Other services | 2017 |
| Concept Construction (Ribble Valley) Ltd | Construction | 2020 |
| Concept Homes and Investments Ltd | Real estate | 2025 |
| Concept Landscapes Limited | Construction | 2013 |
| Concept Works Design Ltd | Professional & scientific | 2021 |
| Conception Design Associates Limited | Other services | 2019 |
| Concepts 2000 PLC | | 2008 |
| Conclave Ltd | Information & communication | 2025 |
| Confused Cat Ltd | Wholesale & retail | 2025 |
| Conlin Group Ltd | Other services | 2023 |
| Conlon (EOT) Limited | Financial services | 2024 |
| Conlon Construction Limited | Construction | 1961 |
| Conlon Holdings Limited | Professional & scientific | 2007 |
| Conlon Joinery Ltd | Construction | 2012 |
| Conlon Living Limited | Construction | 2016 |
| Connaught Coachworks Ltd | Extraterritorial | 2014 |
| Connaught Motor Co. (1932) Ltd | Extraterritorial | 2014 |
| Connect Brand Ltd | Manufacturing | 2017 |
| Connect Childcare EBT Trustee Limited | Other services | 2021 |
| Connect Childcare Group Limited | Administrative & support | 2009 |
| Connect Electrical (Worsley) Limited | Construction | 2013 |
| Connect Hire (NW) Limited | Administrative & support | 2015 |
| Connect HR Ltd | Professional & scientific | 2023 |
| Connect Software Solutions Ltd | Information & communication | 2004 |
| Connect the Tots Ltd | Arts & recreation | 2026 |
| Connect With Chloe Ltd | Professional & scientific | 2022 |
| Connecting Britain Ltd | Information & communication | 2022 |
| Connection Worx Group Ltd | Information & communication | 2025 |
| Consciousness UK CIC | Professional & scientific | 2022 |
| Conser International Ltd | Financial services | 2020 |
| Conservation Carpentry Limited | Construction | 2024 |
| Consilio Bono Limited | Real estate | 2020 |
| Consort Healthcare (Birmingham) Funding PLC | Health & social care | 2005 |
| Consort Healthcare (Birmingham) Holdings Limited | Financial services | 2005 |
| Consort Healthcare (Birmingham) Intermediate Limited | Professional & scientific | 2005 |
| Consort Healthcare (Birmingham) Limited | Health & social care | 2005 |
| CONSORTIUM24 LLP | | 2024 |
| Constabley Investments Limited | Professional & scientific | 2018 |