| CHP Projects Limited | Real estate | 2025 |
| Chris Coving Limited | Construction | 2020 |
| Chris Woolf Rail Services Limited | Professional & scientific | 2024 |
| Christine Griffiths Consultancy Ltd | Extraterritorial | 2012 |
| Christopher Stewart Lampitt Limited | Extraterritorial | 2024 |
| Chrysoberyl Investments and Holdings Ltd | Financial services | 2022 |
| Chung Coffee Ltd | Hospitality | 2021 |
| Churley Media Services Ltd | Professional & scientific | 2024 |
| CIF Contractors Ltd | Construction | 2020 |
| Cignet Engineering Management Associates Limited | Professional & scientific | 2017 |
| Cinder's Cleaning Services Limited | Administrative & support | 2017 |
| Cintra Limited | Wholesale & retail | 2026 |
| CIP Construction Ltd | Construction | 2015 |
| CIP Invest Ltd | Real estate | 2024 |
| Circa Press Limited | Information & communication | 2004 |
| Circus Properties Ltd | Real estate | 2015 |
| Citizens Workshop Ltd | Real estate | 2022 |
| City Alarms Limited | Administrative & support | 2000 |
| City Cladding Ltd | Construction | 2017 |
| City Lettings London Ltd | Real estate | 2015 |
| City Property Solutions Ltd | Real estate | 2024 |
| City Rail and Construction Limited | Professional & scientific | 2021 |
| Citywala Ltd | Real estate | 2019 |
| Civinity Engineering UK Ltd | Construction | 2020 |
| Civinity UK Ltd | Construction | 2021 |
| CJ Investment Property Ltd | Real estate | 2023 |
| CJ21 Properties Limited | Real estate | 2015 |
| CJA Contracts Limited | Construction | 2015 |
| CJA Heating Ltd | Construction | 2015 |
| CJC IT Consultants Ltd | Information & communication | 2017 |
| CJD Investments Ltd | Real estate | 2019 |
| Cjhascare Limited | Wholesale & retail | 2015 |
| CJM Domestics Limited | Other services | 2017 |
| CK Counselling and Training Services Ltd | Professional & scientific | 2023 |
| CK Design & Builders Ltd | Construction | 2019 |
| CK Pro Construct Limited | Construction | 2025 |
| CKK Capital Ltd | Real estate | 2014 |
| CKK Construction Limited | Construction | 2017 |
| CL Stunts Ltd | Arts & recreation | 2026 |
| Cladelinne Limited | Wholesale & retail | 2023 |
| Clanmor Ltd | Construction | 2012 |
| Claremont Road (45-51) Property Management Company Limited | Households | 1998 |
| Clarity Investment Group London Ltd | Construction | 2019 |
| Claritycounsell Ltd | Health & social care | 2025 |
| Clarityport Ltd | Professional & scientific | 2020 |
| Clark Davies Investments Limited | Real estate | 2019 |
| Clarke & Roberts Ltd | Construction | 2022 |
| Clarkes Cleaning Ltd | Other services | 2025 |
| Classic Car Club Holdings Limited | Financial services | 2000 |
| Classical Edition Vans Limited | Wholesale & retail | 2023 |
| Clavarez Ltd | Health & social care | 2021 |
| Clavarez Properties Ltd | Households | 2024 |
| Clayton Desant Limited | Administrative & support | 2011 |
| Clean Point Ltd | Administrative & support | 2024 |
| Cleaning Attire Care Group Ltd | Other services | 2018 |
| Clear Asset Finance Limited | Financial services | 2010 |
| Clear Business Finance Limited | Financial services | 2019 |
| Clear Construction Finance Limited | Financial services | 2020 |
| Clearstack AI Ltd | Information & communication | 2026 |
| Clearwords.Ai Ltd | Information & communication | 2023 |
| Clermont Group Ltd | Professional & scientific | 2018 |
| Clever Cloggs Day Nursery Limited | Education | 2000 |
| Click Clack Ltd | Wholesale & retail | 2022 |
| Clickaboo Ltd | Wholesale & retail | 2020 |
| Clin-Sync Limited | Information & communication | 2025 |
| Cliproy Limited | Real estate | 1977 |
| Closedbymitch Ltd | Administrative & support | 2025 |
| Cloud Tech Solutions Ltd | Administrative & support | 2023 |
| Cloudatagrid Solutions Limited | Information & communication | 2019 |
| Clouded Minds Limited | Manufacturing | 2013 |
| Cloudessentials Ltd | Information & communication | 2017 |
| Cloudstruct Ltd | Construction | 2025 |
| Clovertronix Ltd | Manufacturing | 2021 |
| Clubforge AI Limited | Information & communication | 2026 |
| Clyne Clothing Limited | Wholesale & retail | 2025 |
| CM Planning Limited | Construction | 2018 |
| Cmbotha Limited | Health & social care | 2023 |
| CMD Investments Ltd | Professional & scientific | 2004 |
| CMG UK Properties Limited | Real estate | 2016 |
| CMP Property Limited | Administrative & support | 2018 |
| CMS Floors Ltd | Construction | 2019 |
| CMU People Services Ltd | Health & social care | 2025 |
| CND Model Management Limited | Administrative & support | 2024 |
| CNE Property Holdings Ltd | Real estate | 2026 |
| Cnpr Holding Limited | Construction | 2018 |
| Cnsn Ltd | Construction | 2024 |
| Co-Living Collective Ltd | Real estate | 2021 |
| Coached by Helen Ltd | Other services | 2025 |
| Coaching With Jack Ltd | Arts & recreation | 2021 |
| Coansah Limited | Wholesale & retail | 2015 |
| Coastdene Limited | Administrative & support | 2017 |
| Cobblestones Estates Limited | Real estate | 2021 |
| Coberry Limited | Professional & scientific | 2008 |
| Cocajeti Limited | Real estate | 2012 |
| Cocayo Limited | Education | 2013 |
| Cockney Rejects Limited | Arts & recreation | 2016 |
| Coco Buttons Ltd | Wholesale & retail | 2020 |
| Cocoon Children Services Ltd | Health & social care | 2021 |
| Cocoon Investments Limited | Real estate | 2024 |
| Coders HUT Limited | Information & communication | 2017 |