| Church Farm Conversion Ltd | Real estate | 2020 |
| Church Street Management (Charvil) Limited | Households | 2022 |
| Church Views Associates RTE Limited | Administrative & support | 2006 |
| Churchfield Care Limited | Health & social care | 2020 |
| Chutnei Charm Hounslow Limited | Hospitality | 2026 |
| Chutnei Charm Uxbridge Limited | Hospitality | 2026 |
| CI Collective Studio Limited | Professional & scientific | 2024 |
| Ciazer B2B Law Associates Limited | Professional & scientific | 2020 |
| CIF Services Limited | Administrative & support | 2018 |
| CIG Group Ltd | Financial services | 2025 |
| CIG Services Limited | Professional & scientific | 2016 |
| Cigma IT Solutions Limited | Information & communication | 2008 |
| Cigul Information Technology Ltd | Information & communication | 2025 |
| Cina Limited | Information & communication | 2026 |
| Cinatt Limited | Professional & scientific | 2018 |
| Cinelab Film and Digital Limited | Information & communication | 2021 |
| Cinelab London Limited | Information & communication | 2008 |
| Cinelabs International Ltd | Financial services | 2013 |
| Cipher Cars Ltd | Wholesale & retail | 2024 |
| Ciphergate Limited | Information & communication | 2026 |
| Cippenham Halal Meat Ltd | Wholesale & retail | 2024 |
| Cippenham Lane (Slough) Management Company Limited | Professional & scientific | 1982 |
| Cippenham Lane Fish & Chips Ltd | Hospitality | 2018 |
| Cippenham Select Doner Ltd | Hospitality | 2024 |
| Cippenham Store Limited | Wholesale & retail | 2013 |
| Ciprian PA Transport Ltd | Transport & logistics | 2026 |
| Circet Freeflow Limited | Administrative & support | 2018 |
| Circular Feedstock Services Limited | Manufacturing | 2019 |
| Cirrus Cloud Ltd | Extraterritorial | 2011 |
| CIS Worldwide Ltd | Information & communication | 2017 |
| Cissh Commercial Limited | Construction | 2026 |
| Cissh Developments Limited | Construction | 2014 |
| Cissh Property Management Limited | Real estate | 2014 |
| Citadel Design & Development Limited | Professional & scientific | 2007 |
| Cite Services Limited | Professional & scientific | 2019 |
| Citi Autos Ltd | Wholesale & retail | 2013 |
| City 1ST Holdings Limited | Financial services | 2025 |
| City Alpha Ltd | Construction | 2021 |
| City Carpets & Furniture Ltd | Wholesale & retail | 2016 |
| City Expert Facility Management Ltd | Construction | 2024 |
| City Fruit & VEG Limited | Wholesale & retail | 2020 |
| City Furnisher Ltd | Wholesale & retail | 2026 |
| City Law Immigration Ltd | Professional & scientific | 2013 |
| City Property Berkshire Ltd | Real estate | 2022 |
| City West Support Services Limited | Administrative & support | 2010 |
| Cityflow Plumbing Limited | Construction | 2025 |
| Citygateuk Ltd | Wholesale & retail | 2021 |
| CITYM3D Limited | Manufacturing | 2018 |
| Citymoor Estate Agents Ltd | Wholesale & retail | 2020 |
| Citymoor Financial Ltd | Financial services | 2019 |
| Citymoor Protection Ltd | Financial services | 2019 |
| Citywide Trading (UK) Limited | Information & communication | 2008 |
| Ciuches Construction Ltd | Construction | 2023 |
| CJ Electrical Services Limited | Construction | 2002 |
| CJ Estates Collection Ltd | Real estate | 2025 |
| CJ House Ltd | Public administration | 2017 |
| CJC Trading Services Ltd | Construction | 2024 |
| CJI Logistics Ltd | Construction | 2026 |
| CJR Capital Investments Ltd | Real estate | 2019 |
| CK & MK Ltd | Wholesale & retail | 2019 |
| CK & MS Properties Ltd | Real estate | 2023 |
| CK Carpets Limited | Wholesale & retail | 2003 |
| CK Coaching Ltd | Health & social care | 2019 |
| CK Hospitality Global Ltd | Hospitality | 2025 |
| CK Trucking Ltd | Transport & logistics | 2023 |
| CKJ Properties London Limited | Real estate | 2022 |
| CKS Ltd | Manufacturing | 2009 |
| Ckuk Estates Ltd | Real estate | 2022 |
| CL SPV 1 Limited | Real estate | 2023 |
| CL SPV2 Limited | Real estate | 2023 |
| CL SPV3 Limited | Construction | 2026 |
| Claire White Events Limited | Administrative & support | 2015 |
| Clarence Park Care Limited | Health & social care | 2020 |
| Clarity Venture Support Ltd | Professional & scientific | 2025 |
| Clark Carpentry & Construction Ltd | Construction | 2018 |
| Clarkswell Limited | Professional & scientific | 2009 |
| Clasic Security Limited | Administrative & support | 2024 |
| Classic Customs Global Ltd | Wholesale & retail | 2023 |
| Classic Metals Ltd | Manufacturing | 2022 |
| Classic Recruitment Ltd | Administrative & support | 2013 |
| Classic Services Ltd | Other services | 2019 |
| Classico Marble Ltd. | Construction | 1995 |
| Classtutor Services Ltd | Education | 2024 |
| Classy VIP Chauffeurs Ltd | Transport & logistics | 2017 |
| Clatrian Services Limited | Other services | 2014 |
| Clavis Property Ltd | Hospitality | 2019 |
| Clay Leaf Developments Limited | Real estate | 2014 |
| Clayton Oak Properties Limited | Real estate | 2015 |
| Clean Build Facilities Ltd | Construction | 2025 |
| Clean DRY Cleaners & Launders Limited | Other services | 2018 |
| Clean Wave Energy Ltd | Construction | 2022 |
| Cleanova Ltd | Administrative & support | 2026 |
| Cleanpure (UK) Ltd | Wholesale & retail | 2021 |
| Cleansqft Ltd | Administrative & support | 2025 |
| Cleansweep Services Limited | Administrative & support | 1999 |
| Cleanzing Services Co. Limited | Transport & logistics | 2023 |
| Clear Associates Limited | Professional & scientific | 2009 |
| Clear Business Solutions Ltd | Professional & scientific | 2026 |
| Clear Consultants Ltd | Professional & scientific | 2023 |
| Clear Image Solutions Ltd | Manufacturing | 2008 |