| Complex Continence Management & Training Limited | Health & social care | 2020 |
| Compliance Fire Protection Limited | Professional & scientific | 2022 |
| Comprehensive to Basic Data Solutions Limited | Construction | 2016 |
| Compruse Ltd | Transport & logistics | 2024 |
| Comptec Holdings Limited | Financial services | 2019 |
| Comptec Limited | Manufacturing | 1996 |
| Computaaz Ltd | Information & communication | 2025 |
| Computacables Limited | Manufacturing | 2010 |
| Computer & Data Supplies Ltd | Other services | 2022 |
| Computercentric Ltd | Information & communication | 2014 |
| Comtake Engineering Limited | Construction | 2003 |
| Comts Healthcare Ltd | Health & social care | 2022 |
| Concept Extru-Tech Limited | Administrative & support | 2003 |
| Concept Solutions 2009 Limited | Financial services | 2008 |
| Concrete Capital Holdings Ltd | Real estate | 2018 |
| Concrete Rose Interiors Ltd | Professional & scientific | 2020 |
| Confessions Tattoo Studio Ltd | Arts & recreation | 2025 |
| Conlon Pubs Ltd | Hospitality | 2024 |
| CONNEC2DOTS Consultancy Limited | Professional & scientific | 2024 |
| Connect Courier Express Ltd | Transport & logistics | 2021 |
| Connect Estates Ltd | Real estate | 2025 |
| Connect Fire & Security Limited | Construction | 2015 |
| Connect Therapeutic Community Limited | Real estate | 1998 |
| CONNECT2CAMPUS Ltd | Education | 2019 |
| Connekt Solutions Ltd | Health & social care | 2015 |
| Connoisseurs of Couture Limited | Wholesale & retail | 2018 |
| Connor James Properties Ltd | Real estate | 2019 |
| Connor Metcalf Properties Ltd | Real estate | 2025 |
| Connvex Ltd | Information & communication | 2026 |
| Conrad Anderson Ltd | Wholesale & retail | 2018 |
| Conrom Ltd | Construction | 2025 |
| Constant Floors Limited | Extraterritorial | 2022 |
| Constantine Close Protection Ltd | Administrative & support | 2026 |
| Construct Training Courses Ltd | Professional & scientific | 2025 |
| Construction Accessories Limited | Arts & recreation | 1984 |
| Construction Solutions and Consultancy Service Ltd | Construction | 2024 |
| Constructionize Construction Company Ltd | Construction | 2019 |
| Constructions Giovanni Ltd | Construction | 2019 |
| Consult and Design International Limited | Information & communication | 2005 |
| Contact Retail Group Ltd | Real estate | 2025 |
| Contain-A-Lock Limited | Extraterritorial | 2005 |
| Containers Online Ltd | Extraterritorial | 2016 |
| Content Designed Ltd | Professional & scientific | 2019 |
| Contesse Floors UK Limited | Extraterritorial | 2022 |
| Continental Beautie Limited | Wholesale & retail | 2014 |
| Contract Design Solutions Limited | Wholesale & retail | 2022 |
| Contract Review and Training Services Limited | Professional & scientific | 2022 |
| Control Systems Design Limited | Manufacturing | 2004 |
| Controlled Labour Solutions Ltd | Administrative & support | 2026 |
| Convertall Ltd | Manufacturing | 2010 |
| Conway Packing Properties Limited | Real estate | 2016 |
| Conway Packing Services Holdings Limited | Professional & scientific | 2003 |
| Conwy Valley Railway Museum Limited | Other services | 1975 |
| Cooke Brothers Limited | Manufacturing | 1953 |
| COOKIE2031 Ltd | Hospitality | 2026 |
| Cool Fish Communication Limited | Information & communication | 1999 |
| Cool HOG Ltd | Manufacturing | 2021 |
| Cool Running Refrigeration Ltd | Manufacturing | 2014 |
| Cool-Therm (Consultants) Limited | Professional & scientific | 2013 |
| Cool-Therm (Group) Limited | Construction | 2016 |
| Cool-Therm (Holdings) Limited | Financial services | 2008 |
| Cool-Therm (South East) Limited | Construction | 2018 |
| Cool-Therm (South West) Limited | Construction | 2018 |
| Cool-Therm (UK) Limited | Construction | 1992 |
| Cool-Therm (Wales) Limited | Extraterritorial | 2008 |
| Cooper Asset Management Ltd | Financial services | 2022 |
| Cooper Cladding P Ltd | Construction | 2022 |
| Cooper Entertainment Services Ltd | Arts & recreation | 2019 |
| Cooper's Family Butchers Limited | Wholesale & retail | 2003 |
| Cooperfields Limited | Professional & scientific | 2021 |
| Coorbist Ltd | Transport & logistics | 2024 |
| Coporod Ltd | Water & waste | 2026 |
| Copper & Non-Asbestos Washer Company Limited(The) | Professional & scientific | 1984 |
| Copper Beech Construction Services Limited | Construction | 2018 |
| Copper River Holdings Ltd | Financial services | 2025 |
| Corbett Pharma Ltd | Wholesale & retail | 2024 |
| Cordicish Ltd | Wholesale & retail | 2024 |
| Core Essence Ltd | Wholesale & retail | 2024 |
| Core Improvement Solutions Ltd | Professional & scientific | 2011 |
| Core Line Consultancy Ltd | Professional & scientific | 2024 |
| Corebridge Properties Ltd | Real estate | 2025 |
| Corenova Health Ltd | Professional & scientific | 2025 |
| Corfields (Walsall) Limited | Wholesale & retail | 2019 |
| Corn Transport Ltd | Transport & logistics | 2023 |
| Corner Mechanics Limited | Wholesale & retail | 2026 |
| Cornermax Ltd | Wholesale & retail | 2025 |
| Cornerstone Property Solutions (UK) Ltd | Construction | 2011 |
| Cornick Productions Ltd | Information & communication | 2020 |
| Cornish Holiday Lodges Limited | Real estate | 2007 |
| Coronation Walk Management Company Limited | Households | 2011 |
| Corporate Claims Specialists Limited | Other services | 2006 |
| Corporate Service Providers Limited | Professional & scientific | 2025 |
| Corradova Properties Limited | Households | 1988 |
| Corron Properties Ltd | Administrative & support | 2025 |
| Corroy Products Limited | Wholesale & retail | 1978 |
| Corvetune Ltd | Wholesale & retail | 2024 |
| Coseley Fish Bar Limited | Hospitality | 2013 |
| Cosmetix Limited | Wholesale & retail | 2013 |
| Cospire Limited | Wholesale & retail | 2024 |
| Costcutter Patel Ltd | Wholesale & retail | 2014 |