| City Irrigation Limited | Manufacturing | 1986 |
| City Massage & Well-Being Ltd | Health & social care | 2014 |
| City Ringbinders Limited | Administrative & support | 2002 |
| Cityfix Plumbing and Heating Ltd | Construction | 2026 |
| Citymaas Ltd | Information & communication | 2019 |
| CIYO6262 Limited | Hospitality | 2025 |
| CJ Plumbing & Build Limited | Construction | 2019 |
| CJ Roofing (London) Ltd | Construction | 2021 |
| CJG Professional Services Limited | Professional & scientific | 2011 |
| CJP Commissioning Ltd | Professional & scientific | 2022 |
| CJW Communications Ltd | Professional & scientific | 2019 |
| CK Prestige Cleaning Ltd | Administrative & support | 2024 |
| CK Safety Consultancy Limited | Professional & scientific | 2014 |
| Ckir Consultancy Ltd | Administrative & support | 2011 |
| CKM Accountancy Ltd | Professional & scientific | 1997 |
| Ckss Solutions Limited | Administrative & support | 2014 |
| CL & HL Investments (Hayes) Ltd | Real estate | 2026 |
| CL & HL Investments Ltd | Real estate | 2017 |
| CL GOH Limited | Health & social care | 2015 |
| CL Investments Limited | Financial services | 2019 |
| CL Performing Arts Ltd | Arts & recreation | 2018 |
| Claddagh Holdings Limited | Financial services | 2022 |
| Claimline Legal UK Limited | Professional & scientific | 2010 |
| Clairenel Limited | Administrative & support | 2018 |
| Claremont Ice Cream (Dartford) Limited | Real estate | 1965 |
| Claremont Securities Limited | Real estate | 1971 |
| Clario Vision Ltd | Health & social care | 2025 |
| Clarityml Consulting Limited | Information & communication | 2026 |
| Clark Accounting Limited | Professional & scientific | 2025 |
| Clark-Wright Holdings Limited | Financial services | 2025 |
| Claroblue Design Consultants Limited | Professional & scientific | 2010 |
| Clash Productions Limited | Administrative & support | 2019 |
| Classical Broadcast Ltd | Information & communication | 2021 |
| Claud Investments Ltd | Real estate | 2018 |
| Claudio Boakye Ltd | Transport & logistics | 2025 |
| Clavaxco Technology Limited | Information & communication | 2021 |
| Clavelshay Hats Limited | Education | 2023 |
| Clean and Sparkle Solutions Ltd | Administrative & support | 2020 |
| Clean Deal Boiler Services Limited | Construction | 2021 |
| Cleancanvasuk Ltd | Administrative & support | 2024 |
| CLEANERS2MATCH Ltd | Construction | 2022 |
| Cleanq Limited | Administrative & support | 2016 |
| Clear Clause UK Ltd | Professional & scientific | 2025 |
| Clear CUT Properties Limited | Construction | 2023 |
| Clear Engineering Recruitment Ltd | Administrative & support | 2017 |
| Clear Recruitment Group Ltd | Administrative & support | 2024 |
| Clear@Home Limited | Construction | 2021 |
| Clearance NO1 Ltd | Transport & logistics | 2019 |
| Clearcut Services Ltd | Other services | 2025 |
| Clearplate Ltd | Hospitality | 2026 |
| Clearview Window Cleaning Specialists Ltd | Administrative & support | 2020 |
| Cleary Court Vicarage Crescent Limited | Households | 2018 |
| Clegeo Consulting Ltd | Information & communication | 2025 |
| Clements Close (Wallace Land) Management Company Limited | Households | 2013 |
| Clements Electrical Services Limited | Construction | 2023 |
| Clerks Industrial Plumbing Ltd | Construction | 2016 |
| Clever Clogs Child Care Ltd | Education | 2006 |
| Cleverbox UK Ltd | Manufacturing | 1999 |
| Clewley Investments Limited | Financial services | 1986 |
| Click Quote Ltd | Professional & scientific | 2026 |
| Clifford Court Limited | Real estate | 1982 |
| Climate Solutions Agency Ltd | Professional & scientific | 2023 |
| Clinifi Cleaning Service Ltd | Administrative & support | 2025 |
| Clip Theatre Ltd | Education | 2020 |
| Cliqk Ltd | Information & communication | 2022 |
| Clive and Crew Ltd | Administrative & support | 2023 |
| CLM Consultants Limited | Information & communication | 2016 |
| Clocktower Property Ltd | Real estate | 2024 |
| Clockwork Contracting Limited | Administrative & support | 2022 |
| Clothes Hire Project Ltd | Wholesale & retail | 2024 |
| Cloud Inn Ltd | Households | 2022 |
| Cloud Tech Holdings Limited | Financial services | 2025 |
| Cloudberry Property Limited | Real estate | 2022 |
| Cloudkeeper Accounting, Bookkeeping & Tax Ltd. | Professional & scientific | 2018 |
| Cloudmind AI Limited | Information & communication | 2023 |
| Cloudtec Limited | Administrative & support | 2014 |
| CLOUDTOUCH360 Ltd | Other services | 2024 |
| Cloudwick UK Limited | Information & communication | 2020 |
| Clover Club Ltd | Hospitality | 2026 |
| Clownalley Limited | Real estate | 2007 |
| CLS Property Partners Limited | Real estate | 2018 |
| Club 414 Brixton Limited | Hospitality | 2019 |
| Club 414 Limited | Hospitality | 2019 |
| Club 414 London Limited | Hospitality | 2019 |
| Club Cardonor Limited | Manufacturing | 2024 |
| Clubb Cannon Drainage Ltd | Construction | 2015 |
| Clutch Media and Entertainment Limited | Information & communication | 2019 |
| CM Capital Investments Ltd | Professional & scientific | 2019 |
| CMD (LDN) Ltd | Other services | 2019 |
| Cmfc Accounting Limited | Professional & scientific | 2015 |
| CMH Vehicle Valet and Detailing Ltd | Administrative & support | 2022 |
| CMJ Music Limited | Arts & recreation | 2015 |
| Cmmr Limited | Administrative & support | 2024 |
| Cmrj Ventures Limited | Administrative & support | 2022 |
| CMS (Chattaway Mortgage Services) Ltd | Financial services | 2025 |
| CMY Consultants Limited | Financial services | 2014 |
| CN8 Limited | Administrative & support | 2022 |
| CNC Mastery Ltd | Manufacturing | 2019 |
| Co-Efficient Building Design Consultancy Ltd | Professional & scientific | 2014 |
| Co-Production Care Property Ltd | Real estate | 2024 |