| Chris Zuccala Physiotherapy Ltd | Health & social care | 2025 |
| Christa Wright Limited | Health & social care | 2010 |
| Christchurch Close (ST. Albans) Limited | Households | 1994 |
| Christelle Properties Ltd | Real estate | 2024 |
| Christie Interiors Ltd | Administrative & support | 2012 |
| Christmas Creations Ltd | Professional & scientific | 2010 |
| Chroma Cleaners Ltd | Administrative & support | 2026 |
| Chrysanthemum Limited | Information & communication | 2011 |
| CHS Logistics Ltd | Transport & logistics | 2021 |
| Chubby Bear Sales & Marketing Ltd | Professional & scientific | 2024 |
| Chunky Cookies Ltd | Hospitality | 2026 |
| Church Society | Other services | 1926 |
| Church Society Trust | Other services | 1903 |
| Churchill's Confectionery Limited | Manufacturing | 1989 |
| Cibi Labs Limited | Information & communication | 2024 |
| Cibitas Holt Town Limited | Construction | 2004 |
| Cibitas Investments Limited | Construction | 2003 |
| Cicatrix Limited | Information & communication | 2013 |
| Cidb Solutions Ltd | Information & communication | 2022 |
| Cigar Club Limited | Professional & scientific | 1999 |
| Cincinnatus Medical Limited | Health & social care | 2015 |
| Cinderella Hair Limited | Wholesale & retail | 2001 |
| Cinema Collective Hub Limited | Professional & scientific | 2025 |
| Cioli Ltd | Construction | 2017 |
| CIP Logistics Limited | Transport & logistics | 2022 |
| Cipher Stitch Limited | Wholesale & retail | 2025 |
| Cipri Transport Ltd | Transport & logistics | 2020 |
| Ciprian Doncea Ltd | Health & social care | 2019 |
| Ciprian T Design & Build Ltd | Construction | 2023 |
| Ciprianb Limited | Financial services | 2025 |
| Circle E Limited | Financial services | 2022 |
| Circle Trust Developments Limited | Construction | 2024 |
| Circlegreen Residents Association Limited | Households | 1983 |
| Circles Experiences Ltd | Arts & recreation | 2026 |
| Cire Investment Limited | Real estate | 2023 |
| Citi Realty Ltd | Real estate | 2024 |
| Citidrains Ltd | Water & waste | 2013 |
| Citiscape Limited | Construction | 2007 |
| Citizen PAY Ltd | Financial services | 2020 |
| Citrine Management Services Ltd | Professional & scientific | 2023 |
| Citrine Rose Limited | Real estate | 2023 |
| City & Suburban (Car Parks) Limited | Professional & scientific | 2003 |
| City & Suburban Parking Limited | Extraterritorial | 2011 |
| City Fones Ltd | Wholesale & retail | 2026 |
| City Housing Investment Limited | Real estate | 2017 |
| City Jollof Limited | Hospitality | 2025 |
| City Link (Cardiff) Holdings Limited | Professional & scientific | 2003 |
| City Link (Cardiff) Limited | Professional & scientific | 1998 |
| City Living W London Ltd | Real estate | 2023 |
| City Mortgages (London) Ltd | Financial services | 2014 |
| City Shine Cleaners Ltd | Administrative & support | 2023 |
| City Sparks Services Ltd | Construction | 2024 |
| City Water Solutions Ltd | Construction | 2020 |
| Citybound UK Ltd | Information & communication | 1996 |
| Citystaff Solution Limited | Construction | 2025 |
| Ciubotaru Limited | Transport & logistics | 2025 |
| Ciurys Limited | Transport & logistics | 2014 |
| Cizzla Ltd | Wholesale & retail | 2023 |
| CJ Harte Construction Limited | Construction | 2021 |
| CJ Skinhealth Ltd | Other services | 2018 |
| Cjhc Ltd | Information & communication | 2010 |
| Cjmontrose Ltd | Professional & scientific | 2025 |
| CJP Cotswold Tours Limited | Administrative & support | 2022 |
| CJR Consultants Ltd | Professional & scientific | 2025 |
| CJT Electrical Ltd | Construction | 2007 |
| CK London Management Ltd | Real estate | 2024 |
| CK Rigging Ltd | Construction | 2026 |
| CKG Limited | Real estate | 2011 |
| Ckpix Ltd | Information & communication | 2024 |
| CKS Global Solutions Limited | Manufacturing | 2008 |
| CKS Performance Limited | Wholesale & retail | 2002 |
| Clacton Dental Care Ltd | Health & social care | 2011 |
| Claim Hunters Ltd | Administrative & support | 2011 |
| Claire(Berkhamsted)Limited | Professional & scientific | 1961 |
| Clamtek Limited | Information & communication | 2019 |
| Clare Richardson Limited | Other services | 2012 |
| Claremont & Co London Limited | Manufacturing | 2026 |
| Clarendon Living Limited | Administrative & support | 2006 |
| Clarendon Place Services Ltd | Real estate | 2022 |
| Clarets Residential Limited | Real estate | 2010 |
| Clarimil Ltd | Wholesale & retail | 2026 |
| Clarios UK Limited | Wholesale & retail | 1970 |
| Clarke Web Services Ltd | Information & communication | 2025 |
| Clarke's Engineering Ltd | Construction | 2023 |
| Clarkmont Limited | Professional & scientific | 2025 |
| Classic Collections 24/7 Ltd | Wholesale & retail | 2017 |
| Claude Simpson Limited | Professional & scientific | 2019 |
| Claudesign Limited | Information & communication | 2012 |
| Clauss Transport Solutions Ltd. Ltd | Transport & logistics | 2025 |
| Claxton Associates Limited | Financial services | 2001 |
| Clayton & Hayes Limited | Real estate | 1991 |
| CLB Closet Ltd | Wholesale & retail | 2025 |
| CLB Global Group Ltd | Financial services | 2009 |
| CLB Global Holdings Limited | Real estate | 2025 |
| CLB Global Properties Ltd | Construction | 2016 |
| CLB Global Publishing Ltd | Information & communication | 2021 |
| CLC Plumbing & Heating Limited | Other services | 2014 |
| Clean NRG Solutions Ltd | Construction | 2025 |
| Clean Sterrrs Limited | Administrative & support | 2024 |
| Cleanair Products and Services Limited | Manufacturing | 2024 |