| Cwtchy Cwtchy Ltd | Manufacturing | 2013 |
| Cybalign Systems Ltd | Information & communication | 2018 |
| Cyber Smart Squad Limited | Education | 2025 |
| Cybrix Ltd | Wholesale & retail | 2024 |
| CYC Pet Services Ltd | Agriculture & fishing | 2024 |
| Cycadian Limited | Professional & scientific | 2009 |
| Cyclone Ductwork Ltd | Construction | 2023 |
| Cyfannol Medical Practice Ltd | Health & social care | 2025 |
| Cyfeillion Bach Cyfyngedig | Education | 2012 |
| Cymdeithas Gychod Afon Nyfer AC Harbwr Trefdraeth | Arts & recreation | 2006 |
| Cymru Abode Limited | Real estate | 2026 |
| Cymru Football Foundation Limited | Arts & recreation | 1996 |
| Cymru Kitchens Limited | Construction | 1992 |
| Cynefin Farm CIC | Education | 2022 |
| Cynefin Pamoja CIC | Education | 2025 |
| Cyrus Distributions Limited | Wholesale & retail | 2014 |
| D & D Plant Service & Repair Limited | Manufacturing | 2009 |
| D & E Scrap Metals Limited | Water & waste | 2012 |
| D & H J Property Limited | Households | 2017 |
| D & P Elite Solutions Limited | Administrative & support | 2007 |
| D & R Maintenance Solutions Limited | Construction | 2003 |
| D & S Adams Limited | Professional & scientific | 2011 |
| D & S Carpets (IOW) Limited | Wholesale & retail | 2015 |
| D & S Holdings Shropshire Limited | Financial services | 2020 |
| D Collier Services Ltd | Construction | 2019 |
| D Farmer Transport Ltd | Transport & logistics | 2016 |
| D H J Legal Limited | Professional & scientific | 2016 |
| D J Clements Consultancy Services Limited | Professional & scientific | 2022 |
| D J Hunt Fruit and Vegetable Wholesale Ltd | Wholesale & retail | 2026 |
| D J L Rail Limited | Construction | 2018 |
| D L Evans Limited | Professional & scientific | 2010 |
| D Lloyd Carpentry & Development Ltd | Construction | 2024 |
| D P Formwork Ltd | Construction | 2007 |
| D R Lewis Vascular Specialist Services Ltd | Health & social care | 2017 |
| D Squared Maintenance Services Limited | Construction | 2009 |
| D W a Property Solutions Limited | Financial services | 2023 |
| D W Solutions IOW Ltd | Manufacturing | 2025 |
| D Works Traffic Management Ltd | Construction | 2021 |
| D&B Performance Ltd | Wholesale & retail | 2025 |
| D&I Properties Ltd | Real estate | 2025 |
| D&M Warren Holdings Limited | Financial services | 2025 |
| D&N Properties Limited | Real estate | 2025 |
| D&R Maintenance Contractors Ltd | Construction | 2025 |
| D&S Holiday Properties Limited | Hospitality | 2020 |
| D&S Somerton Ltd | Wholesale & retail | 2025 |
| D&T6142 Ltd | Hospitality | 2026 |
| D'Rushah Consultants Limited | Other services | 2023 |
| D-Sig Ltd. | Information & communication | 2006 |
| D. Challis Property Services Ltd | Construction | 2006 |
| D.G. Howell (Hydraulic Engineers) Limited | Manufacturing | 1979 |
| D.J. Howells Heating and Renewables Ltd | Construction | 2014 |
| D.P. Davies (Builders) Limited | Construction | 1994 |
| D.R. Clean Ltd | Administrative & support | 2015 |
| D26 Ltd | Information & communication | 2014 |
| D3 Construction Group Limited | Construction | 2019 |
| Daa-M Property Management Ltd | Households | 2023 |
| DAC Offshore Ltd | Professional & scientific | 2025 |
| Daffodil Properties Developments Limited | Real estate | 2024 |
| Daffodil Properties Holdings Limited | Financial services | 2024 |
| Daffodil Properties Ltd | Real estate | 2023 |
| Daffodil Properties Rentals Limited | Real estate | 2024 |
| Dafshea Limited | Information & communication | 2024 |
| Dafydd Morgan Consultancy Limited | Extraterritorial | 2011 |
| DAH Holdings Ltd | Real estate | 2016 |
| DAH Telecoms Ltd | Information & communication | 2022 |
| DAI Jeffries Ltd | Administrative & support | 2018 |
| DAI Tech Designs Ltd | Information & communication | 2013 |
| Dairy Supplies Limited | Agriculture & fishing | 2008 |
| Dairysmart UK Ltd | Agriculture & fishing | 2024 |
| Daispark Limited | Construction | 2019 |
| Daisy Electrics Limited | Energy | 2026 |
| Daisy Protections Ltd | Information & communication | 2024 |
| Daisychain Innovations Ltd | Professional & scientific | 2025 |
| DAK Consultancy Ltd | Professional & scientific | 2022 |
| Dakra Surveys Ltd | Construction | 2017 |
| Dalaba Limited | Health & social care | 2020 |
| Dallimore Aviation Limited | Professional & scientific | 2021 |
| DAN Biggar Limited | Arts & recreation | 2010 |
| DAN Disinfecting and Neutralising Ltd | Administrative & support | 2020 |
| DAN Kyle Morgan Ltd | Manufacturing | 2024 |
| Dandan Creative Ltd | Information & communication | 2017 |
| Danecourt (Shanklin IOW) Management Company Limited | Households | 1988 |
| Danehurst Management Company (Isle of Wight) Limited | Households | 1979 |
| Dang Capital Group Ltd | Real estate | 2022 |
| Dang Enterprise Ltd | Wholesale & retail | 2021 |
| Dang Holdings Ltd | Real estate | 2022 |
| Dang's Group Ltd | Real estate | 2021 |
| Dangerous Davies Rugby Project Limited | Arts & recreation | 2014 |
| Dangerously Positive C.I.C. | Wholesale & retail | 2024 |
| Dani B Johanson Ltd | Information & communication | 2024 |
| Dani Motors NPT Ltd | Real estate | 2025 |
| Dani Newport Ltd | Hospitality | 2025 |
| Dani Properties NPT Ltd | Wholesale & retail | 2025 |
| Daniel Stimson Surveying Limited | Professional & scientific | 2020 |
| Danielle M&Co Ltd | Wholesale & retail | 2019 |
| Danielmares Ltd | Wholesale & retail | 2020 |
| DANIELMATEIDAVIDE27 Ltd | Transport & logistics | 2024 |
| Danikas Beauty & Aesthetics Ltd | Other services | 2022 |
| Danlar Limited | Construction | 2018 |
| Danmusa Trading Limited | Wholesale & retail | 2025 |