| Dimplec Contractors Ltd | Other services | 2017 |
| Dimtri Food Ltd | Hospitality | 2019 |
| Dinas Integration Services CIC | Wholesale & retail | 2022 |
| Dinefwr Construction Company Limited | Extraterritorial | 1990 |
| Dingley Innovations Ltd | Manufacturing | 2022 |
| Dinu's Pizza Ltd | Construction | 2018 |
| Dinus Restaurant and Pizza and Takeaway Ltd | Hospitality | 2025 |
| Dioara Ltd | Information & communication | 2017 |
| Direct Industrial Products Limited | Wholesale & retail | 2009 |
| Direct Nursing Services Limited | Health & social care | 1998 |
| Direct Storage (Wales) Limited | Transport & logistics | 2011 |
| Direct Supplies (Skewen) Limited | Manufacturing | 2017 |
| Direct Tile Warehouse Limited | Construction | 1997 |
| Direct to Film Limited | Manufacturing | 2023 |
| Directors Choice Limited | Other services | 2014 |
| Dirt Attack Wales Ltd | Administrative & support | 2003 |
| Discount Cars Swansea Ltd | Wholesale & retail | 2024 |
| Discount Carpets & Beds (Swansea) Limited | Wholesale & retail | 2007 |
| Discount-Megastore Ltd | Wholesale & retail | 2025 |
| Discountdigz Properties Ltd. | Real estate | 2019 |
| Distinct Design & Build Limited | Construction | 2006 |
| Distinction Windows Limited | Manufacturing | 1984 |
| Distributor Holdings Limited | Administrative & support | 2001 |
| District Fitness Group Ltd | Financial services | 2018 |
| District Wandsworth Fitness Ltd | Arts & recreation | 2018 |
| Divergent Emergent Community Interest Company | Information & communication | 2024 |
| Divine Beauty by Natalie Ltd | Other services | 2025 |
| Divine Reinvention Ltd | Construction | 2020 |
| Division Pubs Ltd | Hospitality | 2023 |
| Dixon Geos Ltd | Mining & quarrying | 2009 |
| DIY and Gardening Ltd | Wholesale & retail | 2024 |
| DIY Diva Ltd | Construction | 2021 |
| Diyar 23 Limited | Hospitality | 2026 |
| Dizzytrading Limited | Financial services | 2021 |
| DJ Barber Swansea Limited | Other services | 2024 |
| DJ Eyecare Limited | Health & social care | 2014 |
| DJB Mortgages Ltd | Financial services | 2025 |
| DJG Welds Limited | Construction | 2023 |
| DJL Services (Swansea) Limited | Professional & scientific | 2016 |
| DJM Law Limited | Professional & scientific | 2007 |
| DJM Secretarial Services Limited | Administrative & support | 2013 |
| DJP Plumbing and Heating Ltd. | Construction | 2021 |
| Djtm Electrical Services Ltd | Construction | 2016 |
| DJW One Stop Building Company Ltd | Construction | 2022 |
| DK (Carew) Holdings Limited | Mining & quarrying | 2019 |
| DK Engineering Services Limited | Professional & scientific | 2017 |
| DK Network Engineering Limited | Construction | 2023 |
| Dk&M Ltd | Real estate | 2024 |
| DKB Lettings Limited | Real estate | 2026 |
| Dkcr Limited | Transport & logistics | 2024 |
| DKM Hospitality Ltd | Extraterritorial | 2025 |
| DKO Consultancy Limited | Professional & scientific | 2020 |
| DKS (GB) Limited | Wholesale & retail | 2014 |
| DL Garner Properties Limited | Real estate | 2023 |
| Dlamini Limited | Health & social care | 2024 |
| DLE Electrical Ltd | Construction | 2024 |
| DLH Cost & Project Management Limited | Professional & scientific | 2006 |
| DLH Training Solutions Ltd | Other services | 2019 |
| Dlmorse Ltd | Professional & scientific | 2020 |
| Dlpca Ltd | Administrative & support | 2025 |
| DM Asset Management Ltd | Administrative & support | 2021 |
| DM Carpet Clean Ltd | Administrative & support | 2025 |
| DM Catering (Pembs) Limited | Hospitality | 2016 |
| DM Flooring and Tiling Ltd | Other services | 2016 |
| DM Inspection Limited | Professional & scientific | 2015 |
| DMA Plant & Utilities Limited | Construction | 2023 |
| DMC Heavy Industries Ltd | Manufacturing | 2021 |
| DMC Property Services Limited | Real estate | 2025 |
| DMD Roofing and Building Limited | Construction | 2026 |
| DMD Utilities Limited | Construction | 2018 |
| DME Holdings Limited | Real estate | 2018 |
| DMG Systems Limited | Manufacturing | 2003 |
| DMH Properties Swansea Limited | Real estate | 2023 |
| DMO Automotive Ltd | Wholesale & retail | 2025 |
| DMP Competitions Ltd | Administrative & support | 2018 |
| Dmss Property UK Limited | Real estate | 2020 |
| DN Properties Limited | Real estate | 2023 |
| DNA Property Maintenance Ltd | Real estate | 2020 |
| DO - IT Solutions Limited | Professional & scientific | 2003 |
| Do-It Holdings Limited | Professional & scientific | 2018 |
| Dobby Properties Ltd | Real estate | 2016 |
| DOC & DYL Investments Ltd | Real estate | 2023 |
| Dockside Labour Supply Limited | Wholesale & retail | 1999 |
| Doctor Rafique Medical Services Limited | Health & social care | 2016 |
| Doctor Snuggles Music Limited | Information & communication | 1994 |
| Doctors for Healthcare Limited | Professional & scientific | 2025 |
| Doctors Wellbeing Ltd | Administrative & support | 2022 |
| Dogs Bollx Ltd | Wholesale & retail | 2025 |
| Doherty Investments Ltd | Households | 2019 |
| Dolfijn Shipping Limited | Administrative & support | 2021 |
| Dolgader Management Company Limited | Households | 2021 |
| Dolphin Love Cafe Ltd | Wholesale & retail | 2024 |
| Domolly Ltd | Real estate | 2016 |
| DON Ace (Electrical) Limited | | 1972 |
| Don'T Blame IT on the Boogie Ltd | Hospitality | 2024 |
| Donal Hayes & Sons (Building and Civil Engineering) Limited | Construction | 1993 |
| Donal Hayes Construction Limited | Construction | 2006 |
| Donal Hayes Holdings Limited | Professional & scientific | 2006 |
| Donna Percival Limited | Professional & scientific | 2022 |
| Doon Valley Enterprises Limited | Real estate | 2023 |