| Construct for Less Limited | Administrative & support | 2020 |
| Consultant Patient Ltd | Professional & scientific | 2026 |
| Consultingworx Ltd | Professional & scientific | 2019 |
| Contemporary Art Academy Ltd | Wholesale & retail | 2023 |
| Contentclimb Ltd | Professional & scientific | 2026 |
| Contractors International Ltd | Administrative & support | 2019 |
| Cook Consultancy Ltd | Professional & scientific | 2020 |
| Cooltech Air Conditioning Ltd | Energy | 2014 |
| Cooltech Building Services Ltd | Manufacturing | 1994 |
| Copbot Limited | Information & communication | 2018 |
| Copper Box Limited | Real estate | 2013 |
| Copper Horse Contracts Ltd | Construction | 2020 |
| Copper Peak Limited | Professional & scientific | 2019 |
| Copper ROW Coaching Limited | Professional & scientific | 2024 |
| Copperfield House (Windsor) Limited | Households | 2006 |
| Copperfire Ltd | Information & communication | 2014 |
| Coppermill Lock Management Company Limited | Households | 1999 |
| Coppertop Limited | Arts & recreation | 2016 |
| Copson Universe Ltd | Wholesale & retail | 2019 |
| Copt Gilders Management Co. Limited | Real estate | 1981 |
| Coralie Butcher Limited | Administrative & support | 2025 |
| Core Ideals Ltd | Professional & scientific | 2018 |
| Core Search Ltd | Administrative & support | 2025 |
| Corestar Media M&D Productions Ltd | Information & communication | 2025 |
| Cornel House Management (Windsor) Limited | Households | 1977 |
| Cornerstone Fund Placement Limited | Professional & scientific | 2011 |
| Corona Windows Ltd | Construction | 2024 |
| Corrda Ltd | Transport & logistics | 2025 |
| Cosmetic Glow Ltd | Other services | 2021 |
| Cosmia Court Flats Limited | Households | 2005 |
| Coso Holdings Limited | Financial services | 2020 |
| Coso Properties Limited | Real estate | 2026 |
| Costello Production Group Limited | Information & communication | 2021 |
| Cosy Home Style Ltd | Real estate | 2020 |
| Cotton ST Ltd | Wholesale & retail | 2025 |
| Cottrill Mason Limited | Professional & scientific | 2013 |
| Cottura Design Limited | Wholesale & retail | 2018 |
| Counselling Direct Limited | Professional & scientific | 2024 |
| Countisbury Consulting Ltd | Professional & scientific | 2026 |
| County Care Berkshire Limited | Health & social care | 2011 |
| County Decor Ltd | Construction | 2020 |
| Courtwood Residents Management Company Limited | Households | 2022 |
| Cozy Cribs Limited | Construction | 2025 |
| Cozy Giving Holdings Ltd | Information & communication | 2025 |
| Cozy Home Renovation Ltd | Real estate | 2020 |
| CP Bespoke Developments Ltd | Construction | 2025 |
| Craciun Company Limited | Hospitality | 2023 |
| Craft Coop CIC | Wholesale & retail | 2014 |
| Crawford's Electrical Limited | Construction | 2014 |
| Crazy Putt Adventure Golf (Jurassic) Ltd | Arts & recreation | 2017 |
| Crazy Putt Adventure Golf (London) Ltd | Arts & recreation | 2016 |
| Crazy Putt Adventure Golf (Lost World) Ltd | Arts & recreation | 2017 |
| Crazy Putt Adventure Golf (Sparrow Island) Ltd | Arts & recreation | 2017 |
| Creaghton Ltd | Wholesale & retail | 2025 |
| Create Momentum Limited | Professional & scientific | 2012 |
| Creative Collage Ltd | Wholesale & retail | 2012 |
| Creative Merchants Limited | Information & communication | 2013 |
| Creative Republic Limited | Administrative & support | 2003 |
| Creative Workplace Solutions Limited | Administrative & support | 2019 |
| Creatively Controlled Ltd | Professional & scientific | 2025 |
| Creativepotential Consultancy Limited | Education | 2024 |
| Crescendo Financial Planning Limited | Professional & scientific | 2019 |
| Crestwood Design and Build Limited | Administrative & support | 2023 |
| Crestwood Luxury Homes Ltd | Construction | 2025 |
| Cricketers Wharf Residents Management Company Limited | Households | 2017 |
| Cro-Ventures Limited | Professional & scientific | 2018 |
| Crofton Close Residents Association Limited | Households | 1983 |
| Cromwell Court (Harpenden) Management Company Limited | Households | 2016 |
| Cross Road (Sidcup) Management Company Limited | Households | 2020 |
| Crossfit Ascot Limited | Education | 2016 |
| Crown Commercial Limited | Real estate | 2022 |
| Crown Haulage Ltd | Transport & logistics | 2025 |
| Crown Krol Ltd | Wholesale & retail | 2016 |
| Crowncraft Resin Solutions Ltd | Construction | 2025 |
| Crowngoldgallery Ltd | Wholesale & retail | 2024 |
| Crownpyramid Investments Limited | Real estate | 2024 |
| Cruise & Ferry Publications Limited | Information & communication | 2003 |
| Crypto Connect Consulting Ltd | Professional & scientific | 2023 |
| Crystal Associates Limited | Professional & scientific | 2019 |
| CS Partners Medical Limited | Health & social care | 2008 |
| CSF Investments Ltd | Real estate | 2019 |
| CSG International Limited | Arts & recreation | 2015 |
| CSK Architects Limited | Professional & scientific | 2016 |
| Cube Interior Solutions Limited | Construction | 2004 |
| Cube Video Studios Ltd | Information & communication | 2022 |
| Culinaris Inc Limited | Financial services | 2025 |
| Culture Studio Ltd | Extraterritorial | 2019 |
| Cumberland Lodge | Hospitality | 2005 |
| Cumberland Lodge Enterprises Limited | Hospitality | 2005 |
| CUP of Rosie Ltd | Hospitality | 2018 |
| Curly K9 Grooming Limited | Extraterritorial | 2016 |
| Curran Close Residents Association Limited(The) | Households | 1980 |
| Custom Rooflights Limited | Construction | 2017 |
| Customer GIG Limited | Professional & scientific | 2013 |
| Customer Relations Marketing Limited | Professional & scientific | 2001 |
| Cutting Edge Flooring Ltd | Other services | 2006 |
| Cvmc Ltd | Professional & scientific | 2019 |
| CVW Rentals Limited | Real estate | 2025 |
| Cxplora Ltd | Professional & scientific | 2025 |
| Cyberkainos Ltd | Information & communication | 2020 |