| Cognilink Ltd | Other services | 2025 |
| Cohasia Ltd | Information & communication | 2025 |
| Coip Ltd | Wholesale & retail | 2021 |
| Cold Blow Ltd | Information & communication | 2017 |
| Cole END Lane Management Company Limited | Households | 2016 |
| Collett's Limited | Administrative & support | 1997 |
| Columbus Construction & Carpentry Ltd | Construction | 2012 |
| Columbus Sash Windows Ltd | Construction | 2023 |
| Coma Studio Limited | Information & communication | 2015 |
| Common Works Ltd | Professional & scientific | 2015 |
| Community Energy Lower Basset Down C.I.C. | Energy | 2015 |
| Community of Creatives Limited | Arts & recreation | 2024 |
| Community Strength Project CIC | Arts & recreation | 2015 |
| Compact Contracting Services Limited | Agriculture & fishing | 2022 |
| Compass Wealth Ltd | Extraterritorial | 2024 |
| Complete Envelope Design Ltd | Professional & scientific | 2014 |
| Complete Financial Training Ltd | Professional & scientific | 2003 |
| Concours Interiors Limited | Wholesale & retail | 2024 |
| Conscien Limited | Financial services | 2025 |
| Conserge Limited | Administrative & support | 2023 |
| Consilium Land Ltd | Professional & scientific | 2021 |
| Constable Place Management Company Limited | Households | 2020 |
| Constructive Approach Ltd | Other services | 2002 |
| Consul Properties Limited | Real estate | 2015 |
| Consul Sport Limited | Professional & scientific | 2017 |
| Contamac Holdings Limited | Professional & scientific | 2009 |
| Contamac Limited | Manufacturing | 1991 |
| Context Digital Limited | Information & communication | 2023 |
| Continuity Works Ltd | Information & communication | 2025 |
| Contract Care Agency Limited | Health & social care | 1995 |
| Cooinda LLP | | 2024 |
| Cookline Services Limited | Other services | 2008 |
| Cool Ice MAN GB Limited | Other services | 2024 |
| Cooper's Building Surveyors Ltd | Professional & scientific | 2020 |
| Copes Pharmacy Limited | Wholesale & retail | 2002 |
| Copper Dragonfly Ltd | Information & communication | 2019 |
| Copy & Paste Limited | Professional & scientific | 2017 |
| Coram Investments Limited | Financial services | 2026 |
| Corcamb Ltd | Professional & scientific | 2024 |
| Core Collectables & TCG Ltd | Wholesale & retail | 2026 |
| Core Kinetics (EM) Limited | Arts & recreation | 2016 |
| Corn Mill Court Management Limited | Households | 1995 |
| Cornelius J Holdings Ltd | Real estate | 2020 |
| Cornelius James Ltd | Other services | 2018 |
| Cornell Kidman Ltd | Construction | 2014 |
| Cornflowers Management Ltd | Real estate | 2022 |
| Cornwall Consultancy Limited | Information & communication | 2024 |
| Coronation Court (Newmarket) Limited | Households | 2001 |
| Corporate Venturing UK Limited | Extraterritorial | 2002 |
| Cosy Property Limited | Real estate | 2017 |
| Coti Creative Ltd | Information & communication | 2025 |
| Cotleigh Consulting Limited | Administrative & support | 1998 |
| Cotleigh Engineering Co. Limited | Professional & scientific | 1981 |
| Cotleigh Holdings Limited | Professional & scientific | 2005 |
| Cottesmore Holdings Limited | Construction | 2021 |
| Cottesmore Homes Limited | Construction | 2021 |
| Counterpoint Market Intelligence Ltd | Professional & scientific | 2004 |
| Country House Interiors Limited | Wholesale & retail | 2012 |
| Country Style Dachshunds Ltd | Agriculture & fishing | 2020 |
| Courtenay James Ltd | Construction | 2023 |
| Cove Cashmere Limited | Wholesale & retail | 2016 |
| Covenant Property Investment Ltd | Real estate | 2016 |
| Cover Story Entertainment Ltd | Information & communication | 2011 |
| Coverdale Investment Holdings Ltd | Financial services | 2019 |
| Coverstone Holdings Limited | Real estate | 2021 |
| Covert Customers Ltd | Professional & scientific | 2024 |
| COX & Booth Ideas Ltd. | Extraterritorial | 1995 |
| Coyne Properties Limited | Real estate | 2003 |
| CPD Health Ltd | Health & social care | 2023 |
| CQ Design Ltd | Administrative & support | 2019 |
| Crabclaw Limited | Information & communication | 2007 |
| Cranbrook Properties Limited | Real estate | 2013 |
| Create & Brand Limited | Professional & scientific | 2007 |
| Creating Adventurous Places Limited | Construction | 2013 |
| Creative Walden C.I.C. | Arts & recreation | 2017 |
| Creativis Building Construction Limited | Construction | 2019 |
| Crescent Residential Property Management Ltd | Real estate | 2026 |
| Crisp Associates Limited | Real estate | 1960 |
| Crisp Capital Limited | Financial services | 2018 |
| Crocus Grounds Maintenance Limited | Administrative & support | 2014 |
| Crown Lake Properties Limited | Households | 2021 |
| Cscsi Services Limited | Wholesale & retail | 2020 |
| Cult Dog Grooming Co Ltd | Other services | 2026 |
| Cuppaprint Ltd | Administrative & support | 2025 |
| Curlew House Management Company Limited | Households | 2001 |
| Curlew Management RTM Company Limited | Households | 2004 |
| Curryworld (London) Ltd | Hospitality | 2017 |
| Curtin & Co Creations Limited | Arts & recreation | 2025 |
| Curwen Gallery Ltd | Extraterritorial | 2010 |
| Custard Space Limited | Manufacturing | 2015 |
| D and K Vehicle Services Ltd | Wholesale & retail | 2023 |
| D B Site Engineering Ltd | Construction | 2009 |
| D Chisholm Demolition and Groundwork Contractors Limited | Construction | 2020 |
| D Cordall Limited | Other services | 2002 |
| D Limited | Extraterritorial | 2004 |
| D M Carpentry Ltd | Construction | 2025 |
| D Rhodes Heating Limited | Construction | 2019 |
| D. and a. Rayner (Management) Limited | Real estate | 1980 |
| D.S.I. Kitchens & Bathrooms Limited | Households | 2003 |
| Dabit Ltd | Administrative & support | 2011 |