| Chris Hughes Associates Limited | Other services | 2017 |
| Chris Lang Ltd | Arts & recreation | 2011 |
| Chris Lofting Limited | Professional & scientific | 2010 |
| Christopher Street Properties Limited | Real estate | 2009 |
| Chrom Ventures Ltd | Health & social care | 2013 |
| Church Farm Ardeley C.I.C. | Agriculture & fishing | 2002 |
| Churchill Controls Limited | Manufacturing | 1974 |
| Churchmead Management Company Limited | Households | 1988 |
| Churchtown Holdings Limited | Financial services | 2020 |
| Churchward Properties and Construction Ltd | Construction | 2024 |
| Chuter Family Investments Limited | Other services | 2025 |
| Cibus Potum Ltd | Wholesale & retail | 2021 |
| CIE Housewares UK Ltd | Wholesale & retail | 2021 |
| Cinderella Service Limited | Construction | 2025 |
| Cinnabao Ltd | Wholesale & retail | 2021 |
| Cintas Pharma Services Limited | Health & social care | 2004 |
| Circuit Board Arcade Limited | Arts & recreation | 2026 |
| Citadel Security Solutions Ltd | Administrative & support | 2024 |
| City Accountants (London) Limited | Professional & scientific | 2015 |
| City Group Hospitality Ltd | Hospitality | 2021 |
| City Nights Apartments Ltd | Hospitality | 2007 |
| Citygen Technologies Ltd | Information & communication | 2020 |
| Citylifts Installations Limited | Extraterritorial | 2016 |
| Citylifts Services Limited | Extraterritorial | 2016 |
| Civil & Industrial Products Ltd | Construction | 2024 |
| Civilmead Limited | Real estate | 1986 |
| Civo Data Centre (Welwyn) Ltd | Information & communication | 2025 |
| CJ & Son's Recruitment Ltd | Administrative & support | 2024 |
| CJ Marketing Limited | Administrative & support | 2019 |
| CJ Odong Properties Limited | Real estate | 2020 |
| CKM Consultants Ltd | Professional & scientific | 2022 |
| CKM Films Ltd | Information & communication | 2022 |
| CL Carpentry & Building Ltd | Manufacturing | 2022 |
| CL Pictures Ltd | Arts & recreation | 2025 |
| CL SB Rail Limited | Construction | 2018 |
| CLA Property Services Ltd | Construction | 2021 |
| Cladding Remediation Limited | Professional & scientific | 2025 |
| Clara Paris Productions Limited | Information & communication | 2022 |
| Clare's Little Bears Ltd | Health & social care | 2020 |
| Clarenden Barn Limited | Other services | 2019 |
| Clarendon Place Management Company Limited | Households | 2002 |
| Clarion Enterprises Ltd | Construction | 2021 |
| Clarity First Consulting Limited | Professional & scientific | 2016 |
| Clarity PFM Limited | Real estate | 2023 |
| Clarks Sprinklers Ltd | Construction | 2023 |
| Clarkville Ltd | Information & communication | 2007 |
| Clarmore Ltd | Professional & scientific | 2026 |
| Clarmore Representation Ltd | Professional & scientific | 2026 |
| Class Education Limited | Administrative & support | 2013 |
| Class PAY Limited | Professional & scientific | 2013 |
| Claudian Limited | Wholesale & retail | 2021 |
| Clay Building Services Ltd | Construction | 2024 |
| Clean Energy Design Systems Ltd | Manufacturing | 2023 |
| Clean Genies Ltd | Administrative & support | 2020 |
| Clean Nero Ltd | Administrative & support | 2023 |
| Cleaner Gutters Limited | Administrative & support | 2020 |
| Cleanlinks Service Limited | Administrative & support | 2014 |
| Cleanseshield Limited | Administrative & support | 2017 |
| Cleanstays Limited | Real estate | 2024 |
| Clear PAY Payroll Limited | Administrative & support | 2017 |
| Clearcheck Bureau Ltd | Administrative & support | 2025 |
| Clearcut Civils Limited | Construction | 2012 |
| Clearcut Media and Services Limited | Professional & scientific | 2024 |
| Clearix Ltd | Wholesale & retail | 2023 |
| Clearline Drainage Solutions Ltd | Administrative & support | 2026 |
| Clearway Partnership Limited | Professional & scientific | 2026 |
| Cleo Digital Ltd | Professional & scientific | 2020 |
| Clevodon Management Consultancy Ltd | Real estate | 2022 |
| CLF (Online) Ltd | Other services | 2023 |
| Clgrindal Services Limited | Construction | 2022 |
| Clhtrades Ltd | Wholesale & retail | 2025 |
| Click Clean Cleaning Ltd | Administrative & support | 2013 |
| Clientz Biznez Ltd | Administrative & support | 2025 |
| Clifton Supply Limited | Manufacturing | 2019 |
| Clifton Triangle Leisure Limited | Hospitality | 2019 |
| Climate Response Limited | Professional & scientific | 2023 |
| Climax Consulting Limited | Professional & scientific | 2023 |
| Climbing Turn Limited | Manufacturing | 2009 |
| Clincare Limited | Health & social care | 2023 |
| Clinical Care Quality Solutions Limited | Information & communication | 2018 |
| Clinical Guardians Ltd | Professional & scientific | 2016 |
| Clinical Imaging Ltd | Health & social care | 2023 |
| Clint Davis Initiative Ltd | Professional & scientific | 2004 |
| Clinton Pharma Solutions Limited | Professional & scientific | 2026 |
| Clip Story Limited | Information & communication | 2023 |
| CLN Groundwork Ltd | Construction | 2026 |
| Cloud Business Bookkeeping Ltd | Professional & scientific | 2021 |
| Cloud Security Storage Ltd | Administrative & support | 2008 |
| Cloud Social Studio Limited | Professional & scientific | 2026 |
| Cloudvacy CIC | Information & communication | 2025 |
| Club Jupiter Limited | Hospitality | 2025 |
| Club Short Stay Ltd | Hospitality | 2019 |
| CM Experience Ltd | Professional & scientific | 2025 |
| CMB Management Limited | Construction | 2020 |
| CMC Projects LLP | | 2001 |
| CMK Global Limited | Other services | 2020 |
| CMK International Ltd | Administrative & support | 2016 |
| CMS Herts Ltd | Construction | 2011 |
| CMT Project Solutions Ltd | Construction | 2021 |
| CNA Estates Ltd | Real estate | 2025 |