| Clare-Ver Education Ltd | Other services | 2023 |
| Clarea House Ltd | Health & social care | 2022 |
| Claremont Road (Montclare) Management Company Limited | Households | 2015 |
| Clarendon Mews (Colchester) Management Company Limited | Households | 2003 |
| Clarendon Park Residents Company Limited | Households | 2002 |
| Clarks Roofing Ltd | Construction | 2019 |
| Class Click Limited | Administrative & support | 2021 |
| Classic Trade Limited | Information & communication | 2020 |
| Clau Trans Limited | Transport & logistics | 2025 |
| Claudia Medical Consulting Ltd | Health & social care | 2026 |
| Claudiu Logistics UK Ltd | Transport & logistics | 2022 |
| Claya Tech Ltd | Information & communication | 2026 |
| Clean Development Projects Ltd | Professional & scientific | 2010 |
| Cleaning 4U Services Limited | Administrative & support | 2020 |
| Cleanwright Cleaning Services Limited | Administrative & support | 2002 |
| Clear Cremations Ltd | Other services | 2025 |
| Clear Edge - UK Ltd | Manufacturing | 1968 |
| Clear Secure Consultation Ltd | Administrative & support | 2025 |
| Clear Universal Limited | Other services | 2021 |
| Clearfount Services Limited | Health & social care | 2023 |
| Clearpath Media Group Ltd | Information & communication | 2024 |
| Clenoc Limited | Wholesale & retail | 2026 |
| Cleveland Grove (Freehold) Limited | Households | 1997 |
| Cleveland Grove Management Limited | Households | 1993 |
| Clicklight Limited | Administrative & support | 2010 |
| Clina-Excellence Limited | Health & social care | 2023 |
| Clinical Care Consulting Limited | Administrative & support | 2023 |
| Clinikio Limited | Health & social care | 2024 |
| Clique Heating Ltd | Construction | 2021 |
| Clldmn & Bakery Ltd | Wholesale & retail | 2026 |
| Clnruk Ltd | Administrative & support | 2026 |
| Clobella Ltd | Professional & scientific | 2015 |
| Cloud Contracts (UK) Ltd | Construction | 2012 |
| Cloud Technology Hub Ltd | Information & communication | 2025 |
| Cloutify Ltd | Professional & scientific | 2025 |
| Clover Property Services Ltd | Real estate | 2022 |
| Clover Support Group Ltd | Health & social care | 2018 |
| Clovie Studio Ltd | Professional & scientific | 2025 |
| CLS Commissioning Ltd | Professional & scientific | 2026 |
| CLW Projects Limited | Construction | 2017 |
| CLW Property Management Ltd | Real estate | 2024 |
| CLZ Health Ltd | Health & social care | 2022 |
| CM Projects Property Maintenance Ltd | Construction | 2011 |
| CM Social Limited | Health & social care | 2024 |
| CM Tutors Ltd | Education | 2019 |
| CMB Consult Ltd | Financial services | 2017 |
| CMD Collective Limited | Information & communication | 2025 |
| CMG2179 Ltd | Transport & logistics | 2026 |
| CML Signature Properties Ltd | Households | 2025 |
| CNM Services Ltd | Health & social care | 2020 |
| Coach Field Ltd | Professional & scientific | 2021 |
| Coalport Services Community Interest Company | Construction | 2024 |
| Coastal Beans Limited | Hospitality | 2024 |
| Coastal Conveyancing Ltd | Professional & scientific | 2025 |
| Cobblestone Landscapes & Building Ltd | Administrative & support | 2019 |
| Coco's General Services Limited | Hospitality | 2024 |
| Cocolancho Ltd | Real estate | 2024 |
| Code Tech Labs Limited | Information & communication | 2011 |
| Codesse Ltd | Administrative & support | 2015 |
| Coffee Base Limited | Hospitality | 2019 |
| Coffey Consultants Ltd | Professional & scientific | 2021 |
| Coga Properties Limited | Real estate | 2025 |
| Coggeshall West Residents Management Company Limited | Households | 2020 |
| Cognitio Consultare Limited | Information & communication | 2019 |
| Cognitive Hub Group Ltd | Health & social care | 2024 |
| Colada Studio Ltd | Information & communication | 2025 |
| Cold Skill Limited | Manufacturing | 2019 |
| Cole N Cole Limited | Hospitality | 2012 |
| Colebrooke Mews Management Company Limited | Households | 2012 |
| Coles Property Ltd | Professional & scientific | 2015 |
| Colinnorth Limited | Other services | 2016 |
| Collective Fostering Ltd | Health & social care | 2022 |
| College Heath Management Limited | Households | 2006 |
| Colletti Investments Ltd | Real estate | 2020 |
| Collingham Place Limited | Households | 2011 |
| Collins Gyamfi Consultants Limited | Information & communication | 2017 |
| Comdex Data Services Limited | Administrative & support | 1997 |
| Comfort Pillows Ltd | Real estate | 2024 |
| Commercial GAS Group Ltd | Construction | 2025 |
| Commercial Response Limited | Professional & scientific | 2010 |
| Common Room Projects Limited | Other services | 2019 |
| Commonside Mews Management Limited | Households | 1983 |
| Community Embrace UK | Health & social care | 2016 |
| Compago Consultancy Ltd | Education | 2025 |
| Complete BIM Design Ltd | Professional & scientific | 2022 |
| Complete Controls Systems Ltd | Construction | 2018 |
| Complete Data Ltd | Information & communication | 2006 |
| Complete IT Cabling Ltd | Construction | 2009 |
| Complete Refurbishments Limited | Construction | 2015 |
| Completion Digital Limited | Other services | 2020 |
| Completion Law (Three) Limited | Professional & scientific | 2024 |
| Completion Law Limited | Professional & scientific | 2019 |
| CON Mechanical Limited | Construction | 2015 |
| Concept Factory Holdings Limited | Real estate | 2022 |
| Concordia Car Sales Ltd | Wholesale & retail | 2024 |
| Condei Trans Ltd | Transport & logistics | 2017 |
| Condense Construction Solutions Ltd | Construction | 2020 |
| Condense Heating Solutions Limited | Construction | 2014 |
| Cone Scope Limited | Health & social care | 2026 |
| Confiance IT Solutions Ltd | Information & communication | 2012 |