| Carlectrics Limited | Real estate | 1949 |
| Caro Properties Ltd | Real estate | 2021 |
| Caroline Makoni Ltd | Health & social care | 2010 |
| Carpathian Services Limited | Administrative & support | 2008 |
| Carter Wrenn Holdings Limited | Real estate | 2026 |
| Cartland Promotions LLP | | 2021 |
| Casa DI Dolci Limited | Other services | 2012 |
| Casandruc. Ltd | Education | 2018 |
| Castle Cary (BMI) Limited | Real estate | 2016 |
| Castle House (Hertford) Management Limited | Households | 2019 |
| Castledene Leisure Limited | Professional & scientific | 1990 |
| Cat Couriers Ltd | Transport & logistics | 2026 |
| Cathedral Bathrooms Limited | Construction | 2018 |
| Cbmp LLP | | 2020 |
| CC/40 Graham Ltd | Construction | 2019 |
| Ccbgroup(Uk) Ltd | Construction | 2024 |
| CDW Auto Sales Ltd | Wholesale & retail | 2024 |
| Ceci Beauty Salon Limited | Other services | 2023 |
| Cedarmen Couture Ltd | Wholesale & retail | 2026 |
| Celsius Spa Limited | Professional & scientific | 1998 |
| CEM Enterprises Ltd | Arts & recreation | 2013 |
| Cenna Care Ltd | Administrative & support | 2021 |
| Centaurus NHD Holdings Ltd | Administrative & support | 2024 |
| Central Ducts Limited | Construction | 2016 |
| Ceramics & Marble Limited | Construction | 2017 |
| Ceylonpearlseafood Limited | Wholesale & retail | 2026 |
| CF Walthamstow Ltd | Arts & recreation | 2022 |
| CG Contractors (Hertfordshire) Limited | Construction | 2023 |
| CG Property Portfolio Limited | Real estate | 2019 |
| CGC Heating Ltd | Construction | 2020 |
| Cgersh Limited | Health & social care | 2025 |
| CGV Construction Ltd | Construction | 2020 |
| CGV Investments Limited | Real estate | 2024 |
| Chadians Diaspora UK Limited | Education | 2020 |
| Chads Hydraulics Services Ltd | Administrative & support | 2010 |
| Chakraborti Santo 0775 Limited | Health & social care | 2014 |
| Chalmiston Properties Limited | Real estate | 1990 |
| Chandana Enterprises Ltd | Wholesale & retail | 2026 |
| Chapelfield Close Management Limited | Households | 2023 |
| Chapman & Co Butchers Limited | Wholesale & retail | 2025 |
| Char & Barrel Ltd | Hospitality | 2025 |
| Charcoal Meadow Ltd | Administrative & support | 2021 |
| Charge Electrical Limited | Wholesale & retail | 2011 |
| Charles Whitney Limited | Professional & scientific | 1999 |
| Charlotte Bungalows Management Co Ltd | Households | 2024 |
| Charmzz Techs Limited | Information & communication | 2023 |
| Cheer WE Go Ltd | Information & communication | 2023 |
| Cheerful Brigade Limited | Health & social care | 2025 |
| Chelmsford Ultrasound Centre Limited | Health & social care | 2025 |
| Chendoom Limited | Information & communication | 2019 |
| Cherish Social Care Ltd | Health & social care | 2013 |
| Cherokee Consulting Limited | Construction | 2003 |
| Cheshire Oaks Racquets & Healthtrack Limited | Professional & scientific | 1995 |
| Chez L’Habitant Limited | Hospitality | 2023 |
| Child Psychology Solutions Ltd | Health & social care | 2023 |
| Chinez Construction Ltd | Construction | 2019 |
| Chirengendure Limited | Manufacturing | 2015 |
| Chisco Healthcare Limited | Health & social care | 2025 |
| Chisu's Health Care Ltd | Health & social care | 2020 |
| Chiswell Leisure Limited | Wholesale & retail | 2011 |
| Chitic Speed Limited | Transport & logistics | 2017 |
| Chivita Health Limited | Health & social care | 2025 |
| Chobe Ltd | Real estate | 2019 |
| Chocolate Room Ltd | Hospitality | 2025 |
| Chosen Healthcare Ltd | Administrative & support | 2022 |
| Chris Anaetoh Limited | Professional & scientific | 2007 |
| Chrischap Multiservices Limited | Real estate | 2025 |
| Christchurch (Watford) Management Company Limited | Households | 2026 |
| Christian Holdings Ltd | Real estate | 2016 |
| Christine Kendall Couture Limited | Wholesale & retail | 2010 |
| Chtech Limited | Information & communication | 2025 |
| Chundoori Private Limited | Information & communication | 2024 |
| Church Lane (Hatfield) Management Company Limited | Households | 2015 |
| CIA Consultants Limited | Professional & scientific | 2010 |
| Cinepose Limited | Wholesale & retail | 2026 |
| Cinnamon AV Ltd | Construction | 2020 |
| Cinposoft Software Services Ltd | Wholesale & retail | 2020 |
| Ciptrans Ltd | Wholesale & retail | 2020 |
| Circle Plus Security Ltd | Other services | 2020 |
| City Blue Ltd | Administrative & support | 2018 |
| City Drainage Solutions Ltd | Construction | 2018 |
| City Dreams Ltd | Transport & logistics | 2026 |
| City Motors Services Ltd | Wholesale & retail | 2025 |
| Citynest Service Accommodation Ltd | Hospitality | 2025 |
| CJ Groundworks Ltd | Construction | 2020 |
| CJ Woodward Electrical Ltd | Construction | 2024 |
| CK Power UK Private Ltd | Wholesale & retail | 2015 |
| Cladmasters Limited | Construction | 2024 |
| Clarice Properties Ltd | Real estate | 2020 |
| Claridges Court (Hemel Hempstead) Management Company Limited | Households | 2004 |
| Clarity Coaching and Counselling Limited | Health & social care | 2021 |
| Clarke Harrison Ltd | Professional & scientific | 2002 |
| Clarpete Limited | Health & social care | 2013 |
| Clasp of Herts Ltd | Transport & logistics | 2024 |
| Clau CC Transport Ltd | Transport & logistics | 2024 |
| Claudine Collins Consulting Limited | Professional & scientific | 2025 |
| Claudiu Rumpel Ltd | Transport & logistics | 2014 |
| CLB Global Travel Ltd | Administrative & support | 2024 |
| Clean Complete Services Ltd | Administrative & support | 2020 |
| Cleanbusters Limited | Administrative & support | 2025 |