| Crondall House RTM Company Limited | Households | 2020 |
| Cross & Pillory Developments Limited | Construction | 2021 |
| Crown Foodz Ltd | Wholesale & retail | 2025 |
| Crown House Cosmetics Ltd | Professional & scientific | 2002 |
| Crown Jewelz Ltd | Wholesale & retail | 2026 |
| Crownstone Property Services Ltd | Real estate | 2025 |
| Crystal Asset Properties Limited | Real estate | 2024 |
| Crystal Clean London Limited | Other services | 2016 |
| Crystal Ridge Consulting Limited | Administrative & support | 2012 |
| CS 2016 Ltd | Professional & scientific | 2016 |
| CS Live Ltd | Administrative & support | 2022 |
| CSA Properties Limited | Real estate | 2015 |
| Csjr Ventures Limited | Financial services | 2020 |
| CSS Procurement Limited | Other services | 2014 |
| CT Airconditioning Limited | Construction | 2026 |
| Ctpowerline Ltd | Manufacturing | 2023 |
| Cuffley Dental Centre Limited | Health & social care | 2015 |
| Cult and Boutique (Wine Management) Limited | Other services | 2010 |
| Culturedge Ltd | Wholesale & retail | 2013 |
| Culturepot Global Limited | Arts & recreation | 2010 |
| Culverlands Court Residents Association Limited | Households | 1963 |
| Curamed Limited | Health & social care | 2004 |
| Curry Building Limited | Construction | 2018 |
| Curry Popeck LLP | | 2021 |
| Curtains & Blinds Direct UK Ltd | Wholesale & retail | 2006 |
| Custom Operations Transports Limited | Transport & logistics | 2022 |
| CUT and Hedges Gardening Solutions Limited | Administrative & support | 2017 |
| Cute Services Limited | Administrative & support | 2017 |
| Cuzco Limited | Real estate | 1998 |
| CVM Drylining Ltd | Construction | 2025 |
| CWM Property Investments Ltd | Real estate | 2021 |
| CWY (UK) Limited | Wholesale & retail | 2013 |
| Cyber-T Security Ltd | Education | 2015 |
| Cyberliver Limited | Information & communication | 2012 |
| Cybersecurity Solutions Limited | Information & communication | 2018 |
| Cyberskills Training Ltd | Information & communication | 2019 |
| Cyfron Pizza Limited | Hospitality | 2025 |
| Cygeniq UK Limited | Information & communication | 2024 |
| Cygne Limited | Households | 2018 |
| Cymoc Limited | Wholesale & retail | 2015 |
| Cypress Property Services Ltd | Administrative & support | 2024 |
| Cyrildene Limited | Real estate | 2013 |
| Cyzag Limited | Professional & scientific | 2012 |
| D & T Enterprises Limited | Wholesale & retail | 2014 |
| D a Selection Limited | Administrative & support | 2004 |
| D C M 15 Limited | Health & social care | 2016 |
| D Chadha Consulting Ltd | Professional & scientific | 2019 |
| D D Finishes Limited | Construction | 2024 |
| D Hysa Construction Ltd | Construction | 2023 |
| D J W T Limited | Real estate | 2000 |
| D Mcdonnell Haulage Limited | Transport & logistics | 2014 |
| D Pellard Consulting Limited | Professional & scientific | 2013 |
| D&D Maisons Ltd | Professional & scientific | 2020 |
| D&D Security Ltd | Administrative & support | 2023 |
| D&G Fabrication Solutions Ltd | Manufacturing | 2026 |
| D&G RO DRY Lining Ltd | Construction | 2023 |
| D-Gen Limited | Professional & scientific | 1998 |
| D. & M. Cohen Limited | Wholesale & retail | 1978 |
| D.A Couriers / Duktrans Limited | Wholesale & retail | 2020 |
| D3V-ENGINEERING Limited | Construction | 2022 |
| D4 Law Ltd | Professional & scientific | 2011 |
| Dacc (UK) Limited | Professional & scientific | 1997 |
| Dacoe Limited | Professional & scientific | 2018 |
| Daffodils Fostering Ltd | Health & social care | 2016 |
| Daffodils Homes Limited | Administrative & support | 2010 |
| Daily Global Logistics Limited | Transport & logistics | 2013 |
| Dakc Property Services Limited | Real estate | 2013 |
| Daliah Simble Fashion Consultancy Limited | Professional & scientific | 2015 |
| Dalkeith Brokerage Limited | Manufacturing | 2018 |
| Dalkeith Holdings Limited | Financial services | 2018 |
| Damani Finance Ltd | Professional & scientific | 2009 |
| Damirom Ltd | Construction | 2023 |
| Dams Consulting Limited | Information & communication | 2013 |
| DAN Jones Photography Ltd | Professional & scientific | 2012 |
| Dana Luxury Chauffeuring Ltd | Transport & logistics | 2025 |
| Danbro Electrical Services Limited | Construction | 2018 |
| Danbro Services Limited | Construction | 2024 |
| Danco Entertainment Limited | Arts & recreation | 2012 |
| Danelli Properties Limited | Real estate | 2014 |
| Danesfield Manor School Limited | Education | 2021 |
| Daniel Dvorak Ltd | Agriculture & fishing | 2024 |
| Daniel Marian Transport Ltd | Transport & logistics | 2020 |
| Daniel Rose Consulting Limited | Professional & scientific | 2018 |
| Danisha Ltd | Health & social care | 2020 |
| Daniya Properties Limited | Real estate | 2024 |
| Danube Property UK Limited | Real estate | 2025 |
| DAR United FC CIC | Education | 2025 |
| Daradi Ltd | Real estate | 2011 |
| Darayn Consulting Limited | Professional & scientific | 2025 |
| Darcy Financial Services Limited | Real estate | 2026 |
| Darcy Residential Limited | Households | 2020 |
| Dare a Dream CIC | Education | 2023 |
| Daria Express Ltd | Construction | 2018 |
| Darlin Group Limited | Professional & scientific | 2025 |
| Darras Actuarial Services Limited | Professional & scientific | 2018 |
| Darshaan Limited | Other services | 2018 |
| Darvich Limited | Professional & scientific | 2016 |
| Darwin Investments Limited | Extraterritorial | 1959 |
| Data and DEV Services Ltd | Information & communication | 2021 |
| Datamined Capital Ltd. | Financial services | 2020 |