| DAI Mechanical Services Limited | Professional & scientific | 2019 |
| Daicom Limited | Professional & scientific | 2019 |
| DAIO1718 Ltd | Information & communication | 2025 |
| Daiwa House Modular Europe Ltd | Real estate | 2020 |
| DAL Ltd | Professional & scientific | 2020 |
| Dalal Alrajeh Ltd | Professional & scientific | 2022 |
| Daleva Property Group Ltd | Real estate | 2020 |
| Daley Homes Ltd | Construction | 2017 |
| Dalrymple Medical Services Limited | Health & social care | 2020 |
| DAM Insure Ltd | Financial services | 2025 |
| Dammed IF YOU Don’T Ltd | Hospitality | 2025 |
| Damo's Garden Maintenance Ltd | Administrative & support | 2020 |
| Damp Shield (South Wales) Limited | Construction | 2013 |
| Dampearl Luxury Hairs Ltd | Other services | 2025 |
| DAN Leopard Ltd | Health & social care | 2022 |
| Dan-Yr-Ogof (Activities) Limited | Arts & recreation | 1998 |
| Dan-Yr-Ogof France Limited | Other services | 2016 |
| Dan-Yr-Ogof Holdings Limited | Other services | 1952 |
| Dana Medical Services Ltd | Health & social care | 2017 |
| Dancer Engineering Services Limited | Construction | 2024 |
| Dancers International Limited | Arts & recreation | 2002 |
| Dancold Ltd | Construction | 2013 |
| Dande Trading Ltd | Wholesale & retail | 2025 |
| Dandy FOX Domestic Services Limited | Households | 2017 |
| Danem Financial Limited | Professional & scientific | 2016 |
| Daneplan Limited | Real estate | 2000 |
| Daniel Morris Limited | Administrative & support | 2003 |
| Daniel Phillip Dillon Ltd | Extraterritorial | 2025 |
| Daniel Signs Ltd | Other services | 2015 |
| Daniel Vartanov Consultancy Limited | Information & communication | 2021 |
| Danielle D Hair Ltd | Other services | 2022 |
| Danley Investments Limited | Other services | 2017 |
| Danley Properties Limited | Real estate | 2019 |
| Danny Boy's Motor Vehicle Limited | Wholesale & retail | 2022 |
| Danny James Fitness Ltd | Arts & recreation | 2023 |
| Dans Cheese Limited | Wholesale & retail | 2021 |
| Dantek Pumps and Seals Ltd | Manufacturing | 2019 |
| Danvo Limited | Hospitality | 2021 |
| Daob Management Limited | Administrative & support | 2026 |
| Darcsea Limited | Administrative & support | 2024 |
| Darglen Motors Limited | Wholesale & retail | 1973 |
| Dario's Swansea Limited | Hospitality | 2019 |
| Dark Knight Security Services Ltd | Administrative & support | 2015 |
| Darkspeed DS Ltd | Information & communication | 2026 |
| Darlee Ltd | Construction | 2025 |
| Darljays Logistics Ltd | Transport & logistics | 2026 |
| Darlpea Care and Support Services Ltd | Health & social care | 2025 |
| Darmel Media Ltd | Information & communication | 2025 |
| Darmont Construction Limited | Construction | 2018 |
| Darow Equipment Limited | | 2000 |
| Darran Property Limited | Other services | 2020 |
| Darran Property Partnership LLP | | 2007 |
| Darren Hembrow Properties Limited | Real estate | 2025 |
| Darren Jonah Plastering & Building Limited | Construction | 2008 |
| Darren's Cars Limited | Wholesale & retail | 2026 |
| Darrin Davies Consultancy Limited | Professional & scientific | 2025 |
| Dart Amusements Limited | Arts & recreation | 2014 |
| Dart Nation Ltd | Wholesale & retail | 2025 |
| Daryl Morgan Properties Limited | Real estate | 2017 |
| Dasolo Limited | Information & communication | 2025 |
| Data Cabs Swansea Limited | Transport & logistics | 1999 |
| Data Centre Cooling Solutions Limited | Manufacturing | 2025 |
| Data Creative Ltd | Information & communication | 2021 |
| Data-Catch Limited | Administrative & support | 1995 |
| Databid Limited | Construction | 1992 |
| Datavantage Solutions Limited | Information & communication | 2023 |
| Datavoice Ltd | Administrative & support | 2008 |
| Davan Construction Ltd | Construction | 2016 |
| Dave Bright Consulting Ltd | Professional & scientific | 2025 |
| Davey Pymm Ltd | Other services | 2010 |
| Davey's Garage Ltd | Wholesale & retail | 2024 |
| David Alistair Ltd | Wholesale & retail | 2023 |
| David B Williams Consulting Ltd | Professional & scientific | 2013 |
| David Bray Limited | Financial services | 2003 |
| David Brown Holdings Limited | Financial services | 2026 |
| David COE Enterprises Limited | Wholesale & retail | 2003 |
| David Davies (Wholesale Drapers) Limited | Administrative & support | 2008 |
| David G Hodge (International) Ltd | Administrative & support | 1999 |
| David Gascoyne Financial Services Limited | Financial services | 2005 |
| David HAM Autobody Limited | Wholesale & retail | 2014 |
| David Harkness Properties Ltd | Real estate | 2017 |
| David Howes Consulting Ltd | Construction | 2016 |
| David Michael Jewellers Limited | Wholesale & retail | 1996 |
| David Mordecai Travel Ltd | Transport & logistics | 2015 |
| David Morris Properties Ltd | Real estate | 2017 |
| David R Rees Ltd | Professional & scientific | 2010 |
| David Waters Bricklaying Limited | Construction | 2015 |
| David Watkins Legal Limited | Professional & scientific | 2014 |
| Davidge & Sons Painting and Carpentry Ltd | Construction | 2024 |
| Davidson Parcel Delivery Ltd | Transport & logistics | 2026 |
| Davies & Jones One Logistic Ltd | Transport & logistics | 2026 |
| Davies & Jones SW Construction Ltd | Construction | 2026 |
| Davies & Preedy Financial Planning Ltd | Professional & scientific | 2020 |
| Davies & Sons Property Group Limited | Real estate | 2024 |
| Davies and Davies Solicitors Ltd | Professional & scientific | 2022 |
| Davies Building and Carpentry Limited | Construction | 2018 |
| Davies Capital Ltd | Financial services | 2025 |
| Davies Chemists (Briton Ferry) Ltd | Wholesale & retail | 1999 |
| Davies Construction and Groundworks Ltd | Construction | 2023 |
| Davies Groundworks and Construction Ltd | Construction | 2026 |