| Communities Connected C.I.C. | Public administration | 2015 |
| Communities Inc. CIC | Education | 2011 |
| Community Advice and Law Service Ltd | Professional & scientific | 2000 |
| Community Brands UK Limited | Financial services | 2017 |
| Community Careline Services (Westways) Limited | Professional & scientific | 1995 |
| Community Education, Employment & Development Association (C.E.E.D.A) | Education | 2012 |
| Community First Solutions CIC | Professional & scientific | 2024 |
| Community Gate Support Limited | Public administration | 2022 |
| Community Mind Matters Ltd | Health & social care | 2015 |
| Community Sounds and Stories CIC | Manufacturing | 2022 |
| Commuto UK Ltd. | Wholesale & retail | 2018 |
| Companion Care Agency Limited | Health & social care | 2016 |
| Companion Residences Ltd | Health & social care | 2025 |
| Companionship Group Limited | Health & social care | 2025 |
| Company Tech Limited | Information & communication | 2019 |
| Company@Work Limited | Information & communication | 2009 |
| Compass Bulky Services Ltd | Wholesale & retail | 2024 |
| Compass Children's Homes Kent Limited | Health & social care | 2000 |
| Compass Children's Homes Limited | Health & social care | 2001 |
| Compass Children's Homes North East Limited | Health & social care | 2009 |
| Compass Community Ltd | Professional & scientific | 2012 |
| Compass Community Schools Limited | Education | 2023 |
| Compass Fostering Central Limited | Health & social care | 2001 |
| Compass Fostering East Limited | Health & social care | 2005 |
| Compass Fostering London Limited | Health & social care | 1996 |
| Compass Fostering North Limited | Health & social care | 2009 |
| Compass Fostering South Limited | Health & social care | 2013 |
| Compass Fostering Wales Limited | Health & social care | 2006 |
| Compass Fostering West Limited | Health & social care | 2006 |
| Compass P I Limited | Financial services | 2018 |
| Compass Tfas Limited | Health & social care | 2023 |
| COMPASSION24/7 Health and Social Care Ltd | Health & social care | 2017 |
| Compaticare Ltd | Health & social care | 2023 |
| Compec Cleaning Services Ltd | Administrative & support | 2025 |
| Compello Automotive Limited | Administrative & support | 2011 |
| Compendium Amplified Ltd | Professional & scientific | 2018 |
| Comperia Limited | Administrative & support | 2025 |
| Competent Cleaning Team Ltd | Administrative & support | 2021 |
| Complaint Handling Services Limited | Extraterritorial | 2010 |
| Complete Logistics Limited | Transport & logistics | 2013 |
| Complete Bowling Services Limited | Manufacturing | 2008 |
| Complete Detection Systems Limited | Construction | 1988 |
| Complete Driver CPC Training Ltd | Education | 2022 |
| Complete Driveways and Landscapes Ltd | Construction | 2019 |
| Complete IT Services Limited | Other services | 2015 |
| Complete Joinery and Construction Ltd | Construction | 2007 |
| Complete Metering Limited | Information & communication | 2015 |
| Complete Packaging Solutions Ltd | Administrative & support | 2019 |
| Complete Recruit MK Ltd | Administrative & support | 2013 |
| Complete Roof Solutions Limited | Construction | 2009 |
| Complete Savings Ltd | Wholesale & retail | 2025 |
| Complete Solutions Trading Limited | Construction | 2025 |
| Completeshopper Ltd | Wholesale & retail | 2024 |
| Compliance (Air & Water) Limited | Professional & scientific | 2012 |
| Compliance and Privacy Solutions Ltd | Administrative & support | 2018 |
| Compliance for Care Limited | Professional & scientific | 2025 |
| Compliance Wing Limited | Information & communication | 2018 |
| Comply Logistics Limited | Financial services | 2013 |
| COMPOUND3 Ltd | Professional & scientific | 2025 |
| Compressors & Air Equipment Ltd | Manufacturing | 1988 |
| Comptnt Ltd | Education | 2026 |
| Compton Ingenuity Ltd | Hospitality | 2015 |
| Computer Arts Archive CIC | Arts & recreation | 2020 |
| Computer Science Videos Ltd | Information & communication | 2021 |
| Computer Waste Recycling Ltd | Water & waste | 2024 |
| Computerlink (Leicester) Limited | Information & communication | 1995 |
| Comrie Green Limited | Real estate | 2019 |
| Conares UK Limited | Manufacturing | 2021 |
| Concentrically Ltd | Professional & scientific | 2025 |
| Concept 11 Limited | Administrative & support | 2021 |
| Concept Accountancy & Payroll Services Limited | Professional & scientific | 2017 |
| Concept Blind Systems Limited | Manufacturing | 2008 |
| Concept Ceilings Ltd | Construction | 2023 |
| Concept Electrical Contracts Limited | Construction | 2018 |
| Concept Engine Limited | Professional & scientific | 2020 |
| Concept Engineering Consultants Ltd | Construction | 1997 |
| Concept Painting & Decorating Ltd | Construction | 2022 |
| Concept Properties Leicester Ltd | Real estate | 2020 |
| Concept Sourcing Limited | Professional & scientific | 2022 |
| Concepts & Devices Limited | Information & communication | 2010 |
| Concerto Support Services Limited | Information & communication | 2004 |
| Concession Counters Ltd | Hospitality | 2018 |
| Conchee Properties Limited | Construction | 2020 |
| Concility Limited | Manufacturing | 2016 |
| Concord Music Events Ltd | Administrative & support | 2026 |
| Concorde Courier & Cargo Ltd | Transport & logistics | 2021 |
| Concordee Ltd | Health & social care | 2023 |
| Concordia Hospitality Limited | Hospitality | 2020 |
| Concrete Refurbs Ltd | Construction | 2021 |
| Concrete Resin Stencil Driveway Ltd | Construction | 2023 |
| Concrete Rose Ltd | Construction | 2021 |
| Conduit Developments Limited | Construction | 2017 |
| Conduit LSP Ltd | Construction | 2019 |
| Conduruta Transport Limited | Transport & logistics | 2019 |
| Conegliano Ltd | Real estate | 2018 |
| Conerstone Realty Ltd | Real estate | 2025 |
| Conery Consulting Limited | Other services | 2022 |
| Conexion Group Limited | Hospitality | 2019 |
| Conexus Investments Limited | Real estate | 2017 |
| Coneygre Foundry Limited(The) | Extraterritorial | 1925 |