| Communities First Wessex | Transport & logistics | 2012 |
| Commverse Limited | Professional & scientific | 2014 |
| Comovend Limited | Hospitality | 1967 |
| Composite Robotics Ltd | Manufacturing | 2018 |
| Composite Technology Holding Company Limited | Other services | 1989 |
| Comserv (UK) Limited | Other services | 2004 |
| Comserv Projects Limited | Extraterritorial | 2013 |
| Conmax Ltd | Construction | 2025 |
| Connaught Place Management Company Limited | Households | 1997 |
| Connection Marketing Ltd | Professional & scientific | 2025 |
| Connectthings Consultants Ltd | Professional & scientific | 2018 |
| Cooper Smith Developments Limited | Construction | 2019 |
| Coopz Reptiles Ltd | Wholesale & retail | 2022 |
| Cornerstone Portsmouth Ltd | Education | 2023 |
| Cornish Bakehouse UK Limited | Wholesale & retail | 2007 |
| Countless Corals Ltd | Agriculture & fishing | 2025 |
| Country Renewables Limited | Other services | 2023 |
| Cover Storey Architects LLP | | 2016 |
| Cozy Bitch Limited | Wholesale & retail | 2024 |
| CQ Collectables Ltd | Wholesale & retail | 2025 |
| Creating Waves Consulting Ltd | Professional & scientific | 2020 |
| Cripple Creek Guest House Limited | Hospitality | 2002 |
| Critchley Architecture and Design Limited | Professional & scientific | 2018 |
| Crockers Contractors Limited | Mining & quarrying | 2017 |
| Crockers Ltd | Real estate | 2023 |
| Crown Memorials Limited | Wholesale & retail | 1981 |
| Crtc Ltd | Professional & scientific | 2018 |
| CTM Property Maintenance Ltd | Extraterritorial | 2020 |
| Curatrix Holdings Limited | Professional & scientific | 2016 |
| Curatrix Technologies Limited | Information & communication | 2015 |
| Curious Minds Consulting Limited | Professional & scientific | 2016 |
| Curnow & Gunn Accounting Limited | Professional & scientific | 2020 |
| Curzon Square Capital Management Limited | Extraterritorial | 2008 |
| Curzon Square Capital Partners Limited | Administrative & support | 2008 |
| Curzon Square Developments Limited | Administrative & support | 2008 |
| Curzon Square Fund Management Limited | Administrative & support | 2008 |
| Curzon Square Properties Limited | Administrative & support | 2008 |
| Curzon Square Real Estate Limited | Administrative & support | 2008 |
| Curzon Square Strategic Asset Management Limited | Administrative & support | 2008 |
| Custard PIE Creative Ltd | Professional & scientific | 2018 |
| CWC Marketing Ltd | Administrative & support | 2016 |
| Cynspiration Ltd | Information & communication | 2019 |
| D & a Portsmouth Ltd | Manufacturing | 2020 |
| D H Plumbing and Mechanical Ltd | Construction | 2018 |
| D S Clark Roofing Contracting Ltd | Construction | 2015 |
| D Tomlin Groundworks Limited | Construction | 2018 |
| D Woods Garden Services Limited | Administrative & support | 2014 |
| DANI1904 Ltd | Construction | 2019 |
| Daniel Cargo Ltd | Transport & logistics | 2018 |
| Danosa UK Ltd | Manufacturing | 2012 |
| Dapa-Designs Ltd | Manufacturing | 2014 |
| Dark Group Ltd | Information & communication | 1999 |
| Darwin Electrics Ltd | Construction | 2015 |
| Dasis Partners Ltd | Professional & scientific | 2020 |
| Dateraise Limited | Other services | 1982 |
| DBF Creative Ltd | Information & communication | 2012 |
| DC LF UK Bidco Ltd. | Financial services | 2019 |
| Deans Servicing and Repairs Limited | Wholesale & retail | 2019 |
| DEE, Bally & Sons Limited | Hospitality | 2011 |
| Deep Sea Seals Limited | Manufacturing | 2007 |
| Defined Coding Limited | Information & communication | 2019 |
| Delune Limited | Real estate | 2006 |
| Dentamex Ltd | Health & social care | 2014 |
| Dentstem Ltd | Health & social care | 2019 |
| DES Roofing Limited | Construction | 2014 |
| Designbooth Limited | Professional & scientific | 1997 |
| Designer Dens Ltd | Construction | 2021 |
| Devilment Ltd | Real estate | 2000 |
| Diabetes Research and Wellness Foundation | Administrative & support | 1998 |
| Digimas Digital Design Print (UK) Limited | Wholesale & retail | 2016 |
| Digital Butler Ltd | Other services | 2015 |
| Digital Management Ltd | Information & communication | 2015 |
| Digitaldinos Limited | Information & communication | 2016 |
| Dilcon Limited | Manufacturing | 1985 |
| Dima Motors Ltd | Administrative & support | 2021 |
| Direct Management Ltd | Administrative & support | 2017 |
| Distel Straat Limited | Wholesale & retail | 2016 |
| DJ Invest Ltd | Real estate | 2025 |
| DJE Electrical Services & SON Ltd | Construction | 2018 |
| Djs-Ltd Refurbishment Ltd | Construction | 2023 |
| DLM Properties Ltd | Manufacturing | 2009 |
| DM Clothing Limited | Wholesale & retail | 2025 |
| DM GAS and Heating Limited | Construction | 2022 |
| DND Property Limited | Real estate | 2020 |
| Dogan Consultancy Ltd | Health & social care | 2020 |
| Domaine DE Belfortes Scea Limited | Other services | 1990 |
| Doran & Sons Limited | Manufacturing | 1995 |
| Doran Asset Management Limited | Professional & scientific | 2007 |
| Dorin Accounting Limited | Professional & scientific | 2020 |
| Dosky USA Ltd | Hospitality | 2026 |
| Dragon INK Therapy Operations Ltd | Education | 2025 |
| Dream Driveways Limited | Construction | 2026 |
| Dreams and Homes Ltd | Real estate | 2023 |
| Drift IT Limited | Other services | 2005 |
| Driven.Travel Ltd | Administrative & support | 2026 |
| Dromana Wood Investments Ltd | Hospitality | 2006 |
| Drvn Automotive Management Ltd | Information & communication | 2025 |
| Dstar Property Investments Limited | Real estate | 2022 |
| DT Electrical Services Limited | Construction | 2003 |
| DT Precision Ltd | Manufacturing | 1990 |