| Clareways Management Company Limited | Households | 2001 |
| Clarewood Estates Limited | Real estate | 1955 |
| Claridge Park Management Company Limited | Households | 2009 |
| Clarisse Care Limited | Health & social care | 2026 |
| Clarity IT Holdings Limited | Financial services | 2023 |
| Clarity IT Partners LLP | | 2023 |
| Clarity IT Services Limited | Information & communication | 2023 |
| Clarity Minds Ltd | Other services | 2018 |
| CLARITY-K2 Ltd | Public administration | 2026 |
| Clark's Building Contractors Ltd | Construction | 2025 |
| Clarke Court Management Company Limited | Households | 1983 |
| Clarke Innovation Limited | Construction | 2016 |
| Clarkson Investments Limited | Real estate | 2021 |
| Classic and Modern Engine Services Limited | Wholesale & retail | 2002 |
| Classic Car Productions Ltd | Wholesale & retail | 2017 |
| Classic Craft Ltd | Construction | 2022 |
| Classic Sofas Ltd | Wholesale & retail | 2021 |
| Classy Hills Ltd | Other services | 2024 |
| Claudeths Haven Ltd | Real estate | 2024 |
| Claw Mentorship Ltd | Administrative & support | 2025 |
| Clay Croft Management Limited | Households | 1994 |
| Claygate Kebab and Cafe Ltd | Hospitality | 2025 |
| Clayhill Road Management Company Limited | Households | 2007 |
| Clayton & SON Limited | Wholesale & retail | 2004 |
| Clayton Mews (Management) Ltd. | Households | 1994 |
| CLB Construction Ltd | Construction | 2026 |
| CLC Church Limited | Other services | 2019 |
| Clean and Manage London Ltd | Administrative & support | 2017 |
| Clean AS Services Ltd | Administrative & support | 2026 |
| Clean IT Cleaner Limited | Administrative & support | 2016 |
| Clean on Fleek Ltd | Administrative & support | 2023 |
| Clean Sphere: Commercial Cleaning Services Limited | Administrative & support | 2019 |
| Clean to Perfection Ltd | Administrative & support | 2025 |
| Clean&Fluff Ltd | Administrative & support | 2023 |
| Cleaners Direct (London) Ltd | Administrative & support | 2011 |
| Cleaning Comes First Limited | Administrative & support | 2006 |
| Cleaning Spot Ltd | Wholesale & retail | 2008 |
| Cleansmarthouse Ltd | Construction | 2021 |
| Clear ADS Ltd | Information & communication | 2011 |
| Clear Aesthetics Ltd | Extraterritorial | 2022 |
| Clear Business Support Limited | Administrative & support | 2015 |
| Clear Quartz Cleaning Ltd | Administrative & support | 2024 |
| Clearance and Removals Company Limited | Transport & logistics | 2025 |
| Clearance-Services Ltd | Water & waste | 2013 |
| Clearcall Media Ltd | Wholesale & retail | 2025 |
| Clearpath Global Limited | Administrative & support | 2025 |
| Clearshelf Enterprises Ltd | Wholesale & retail | 2025 |
| Clearvision (Brixton) Limited | Health & social care | 1996 |
| Cleary. TV Ltd. | Manufacturing | 2019 |
| Cleaver Baye Soap Company Ltd | Manufacturing | 2025 |
| Clement Associates Ltd | Professional & scientific | 2025 |
| Clemmygates Ltd | Real estate | 2023 |
| Cleo Services Limited | Health & social care | 2006 |
| Clevedon Park Management Company Limited | Households | 2006 |
| Clever Health Care Limited | Health & social care | 2013 |
| Clever Spray Techniques Ltd | Wholesale & retail | 2020 |
| Cleviu Limited | Professional & scientific | 2021 |
| Clewer-Smith Construction Ltd | Construction | 2023 |
| Click 2 World Limited | Wholesale & retail | 2012 |
| Click Entertainment Limited | Wholesale & retail | 2009 |
| Clickcurvemedia Limited | Wholesale & retail | 2025 |
| Clicks and Giggles Ltd | Hospitality | 2025 |
| Clientenabled Limited | Information & communication | 2019 |
| Clients & Business Services Ltd | Administrative & support | 2026 |
| Clifford Blackmore 151 Ltd | Construction | 2021 |
| Clifford Blackmore Commercial Ltd | Construction | 2022 |
| Clifford Blackmore Developments Ltd | Construction | 2020 |
| Clifford Blackmore Investments Limited | Real estate | 2016 |
| Clifton Care Services Limited | Health & social care | 2016 |
| Clifton Court (Freehold) Limited | Households | 2005 |
| Clifton Down House Limited | Households | 2016 |
| Clifton Garden Residents' Association Limited | Households | 1971 |
| Clinicalysis Ltd | Professional & scientific | 2024 |
| Clinks Cufflinks Limited | Manufacturing | 2008 |
| CLK Digital Limited | Hospitality | 2020 |
| CLN Consultancy Limited | Professional & scientific | 2015 |
| Clockwork Camel Ltd | Information & communication | 2011 |
| Clockworknet Limited | Information & communication | 2016 |
| Closepoint Advisory Limited | Information & communication | 2026 |
| Closerthanyesterday Limited | Wholesale & retail | 2021 |
| Cloud 79 (PVT) Ltd | Hospitality | 2026 |
| Cloud Breakthroughs Limited | Information & communication | 2016 |
| Cloud Scribes Ltd | Information & communication | 2021 |
| CLOUD2SPACE Ltd | Information & communication | 2020 |
| Cloudbase Software Limited | Information & communication | 2023 |
| Cloudbytes Consulting Ltd | Information & communication | 2020 |
| Cloudlagom Limited | Information & communication | 2024 |
| Cloudnetworkers Ltd | Administrative & support | 2021 |
| Cloudoption Ltd | Information & communication | 2020 |
| Cloudsynapse Ltd | Information & communication | 2019 |
| Clover Court AB Limited | Real estate | 2024 |
| Clovis Mona Limited | Health & social care | 2024 |
| CLS Cafes Ltd | Hospitality | 2022 |
| CLS Property Associates Limited | Real estate | 2019 |
| Club Football Holdings Ltd | Hospitality | 2024 |
| Club Football Liverpool Ltd | Hospitality | 2024 |
| Club Football London Ltd | Hospitality | 2021 |
| Club Football Manchester Ltd | Hospitality | 2025 |
| Club Football UK Ltd | Hospitality | 2024 |
| Club Yeke Limited | Information & communication | 2021 |