| Connaught Healthcare Limited | Professional & scientific | 2013 |
| Conorco Ltd | Real estate | 2020 |
| Constantin Iosif Ltd | Real estate | 2024 |
| Construction Executive Search Ltd | Administrative & support | 2025 |
| Construserv Ltd | Construction | 2021 |
| Contab Accounting Ltd | Information & communication | 2021 |
| Contar AI Ltd | Professional & scientific | 2025 |
| Cook's Delights Limited | Wholesale & retail | 1996 |
| Copley Residents Association (Stanmore) Limited | Hospitality | 1959 |
| Corneliu Building Ltd | Construction | 2019 |
| Cornhill Capital Limited | Other services | 2021 |
| COS Consulting & Services Limited | Professional & scientific | 2026 |
| Cosmic Energies Limited | Wholesale & retail | 2015 |
| Cosmic Estates Limited | Wholesale & retail | 2019 |
| Cosmo & Co Holdings Ltd | Real estate | 2022 |
| Cosmos Cars Limited | Wholesale & retail | 2024 |
| Cosmos UK Consultancy Limited | Wholesale & retail | 2020 |
| Cottage House Ltd | Real estate | 2018 |
| Cottingham Investments Limited | Real estate | 2014 |
| Counterminers CIC | Arts & recreation | 2024 |
| Covenham Financial Services Limited | Financial services | 1986 |
| Cozira Limited | Information & communication | 2026 |
| CPC Property (2) Limited | Construction | 2023 |
| CPC Property Limited | Real estate | 2014 |
| Craft Studio AI Ltd | Professional & scientific | 2023 |
| Craftiq Limited | Administrative & support | 2024 |
| Cranshaw Ltd | Real estate | 1995 |
| Creative Rhino Limited | Information & communication | 2019 |
| Crepe City Limited | Other services | 2014 |
| Crescente Consulting Ltd | Information & communication | 2022 |
| Crescente Investments Ltd | Real estate | 2022 |
| Crest Point Properties Ltd | Real estate | 2025 |
| Crest Star Motors Limited | Wholesale & retail | 2003 |
| Crispybacon Limited | Information & communication | 2002 |
| Critical Parts Ltd | Wholesale & retail | 2026 |
| CRO Blueprint Limited | Professional & scientific | 2015 |
| Crown Investments (UK) Limited | Professional & scientific | 2004 |
| Cruz Concessions LLP | | 2024 |
| Cssic Media Limited | Extraterritorial | 2020 |
| CU Neurosurgery Ltd | Health & social care | 2019 |
| Cube Concept Systems Ltd | Administrative & support | 2021 |
| Cuby Limited | Information & communication | 2021 |
| Curtainslondon.Com Ltd | Manufacturing | 2005 |
| CV Help 4 U Limited | Professional & scientific | 2009 |
| Cxpeople Limited | Health & social care | 2012 |
| D & a Property Consultancy Ltd | Professional & scientific | 2023 |
| D & H Crow Consultancy Limited | Professional & scientific | 2024 |
| D L Toro Limited | Construction | 2017 |
| D Pindoria Properties Ltd | Real estate | 2020 |
| D.S. Properties (UK) Limited | Real estate | 1989 |
| DA Infinity Consultants Limited | Professional & scientific | 2020 |
| Dachies of London Limited | Other services | 2025 |
| DAD & Daughters TCG Ltd | Wholesale & retail | 2026 |
| Dairy CT Limited | Households | 2025 |
| Danny&Son Construction 2 Ltd | Professional & scientific | 2024 |
| Dany Shafran Limited | Financial services | 2012 |
| Dark Blue Capital Ltd | Professional & scientific | 2019 |
| Dart Associates Ltd | Real estate | 2021 |
| Darwin EYE Consultants LLP | | 2021 |
| Daryll Baker Limited | Health & social care | 2011 |
| DAS & DAS Group Limited | Wholesale & retail | 2016 |
| DAS Entertainment Ltd | Hospitality | 2026 |
| DAS Health Care Ltd | Administrative & support | 2026 |
| Dascal Limited | Education | 2022 |
| Dash Deli Limited | Hospitality | 2009 |
| Data for Business Solutions Ltd | Information & communication | 2023 |
| DATA360 Ltd | Information & communication | 2022 |
| Dataworks Ltd | Information & communication | 2016 |
| David Magnus Limited | Professional & scientific | 2017 |
| Davis & Co Property Group Limited | Real estate | 2022 |
| Dawn of EVE Property Ltd | Construction | 2025 |
| Daya Press Ltd | Arts & recreation | 2026 |
| DC Promanagement Ltd | Professional & scientific | 2009 |
| DDS Tech Ltd | Information & communication | 2026 |
| DE Electrical Services Ltd | Construction | 2022 |
| Dealsmag Ltd | Administrative & support | 2020 |
| Dealsmag Private Services Ltd | Wholesale & retail | 2023 |
| Debeno Limited | Wholesale & retail | 2025 |
| Deco Wood Ltd | Manufacturing | 2023 |
| Deea Chauffeurs Ltd | Transport & logistics | 2025 |
| Deep RAY Limited | Health & social care | 2016 |
| Definovate Ltd | Professional & scientific | 2026 |
| Deftpass Limited | Wholesale & retail | 1984 |
| Deity World Ltd | Wholesale & retail | 2011 |
| Delta One Consulting Limited | Professional & scientific | 2025 |
| Delta Trading Ltd | Financial services | 2026 |
| Denidesigns Ltd | Other services | 2025 |
| Dentnations Limited | Health & social care | 2025 |
| Depot to Door Limited | Wholesale & retail | 2019 |
| Dermray Consulting Limited | Professional & scientific | 2006 |
| Derowski Electrical Ltd | Construction | 2023 |
| Desai Property Holdings Limited | Real estate | 2018 |
| DFD Building Services Ltd | Construction | 2016 |
| DGB Cleaning Services Limited | Administrative & support | 2016 |
| DGC and Partners Ltd | Information & communication | 2021 |
| Dgracing Ltd | Wholesale & retail | 2025 |
| Dharmarajah Limited | Health & social care | 2014 |
| Dhinoja Creations Limited | Extraterritorial | 2024 |
| Diamond Dollz Beauty & Academy Limited | Other services | 2025 |
| Diddy Boilers Ltd | Construction | 2022 |