| Deep Structure Ltd. | Haddington | 2015 |
| Deep Water Corrosion Services (U.K.) Limited | Chichester | 1986 |
| Deepblue ROV Ltd | Ipswich | 2025 |
| Deepsea 7 Ltd | Glasgow | 2019 |
| Deepsea Solutions Ltd | Preston | 2024 |
| Deeptech Developments Limited | | 1994 |
| Deepwater Methods Limited | Glasgow | 2010 |
| Deepwater Well Solutions Limited | Fareham | 2020 |
| Deepwood Mining Company Limited | | 1972 |
| Deering Petrophysical Ltd. | Gillingham | 2017 |
| Deerplay Mines Ltd | Elland | 2017 |
| Deeside Crewing Services Limited | Aberdeen | 2004 |
| Deethya Solutions PVT Ltd | London | 2011 |
| Deka-Company Limited | London | 2025 |
| Delfin Management UK Limited | London | 2019 |
| Delmar Systems Ltd | Aberdeen | 2014 |
| Delonex Chad (One) Limited | London | 2017 |
| Delonex Chad Holdings (One) Limited | London | 2017 |
| Delonex Energy Limited | London | 2013 |
| Delonex Energy UK Limited | London | 2012 |
| Delta Access I Ltd | Torquay | 2017 |
| Delta Energy Limited | London | 2010 |
| Deltic Energy PLC | London | 2012 |
| Delve Mining Solutions Limited | Exeter | 2022 |
| Demerara Resources Limited | London | 2023 |
| Dempster Well Services Ltd | Montrose | 2019 |
| Denakord Ltd | Aberdeen | 2020 |
| Denend Ltd | Edinburgh | 2020 |
| Denfield Well Services Ltd | Montrose | 2005 |
| Denholm Environmental Limited | Glasgow | 2006 |
| Denholm Oilfield Services (Azerbaijan) Limited | Glasgow | 2006 |
| Denispection Consulting ENG. & Inspection Co. Ltd | London | 2023 |
| Denkay Marble UK Limited | London | 2023 |
| Dennis Gillson & SON (Haworth) Limited | Keighley | 1975 |
| Dennis Mckay Services Ltd | Kilmarnock | 2005 |
| Dentaku Ltd | Hampton | 2022 |
| Denteways Ltd | Purley | 2018 |
| DEO Petroleum U.K. Limited | London | 2010 |
| Deovolente Konsult Ltd | Aylesbury | 2021 |
| Derbyshire Aggregates Limited | Bakewell | 1984 |
| Derek Forbes Logistics Limited | Aberdeen | 2007 |
| Derryogue Sand Company Ltd | Newry | 2002 |
| Derwentside Inspection Services Ltd | Consett | 2021 |
| Desert Energy UK Ltd | Birmingham | 2025 |
| Desert Iron Investments Ltd | Cardiff | 2021 |
| Design Point Consulting Limited | London | 2017 |
| Design to Mine Consulting Limited | Warminster | 2010 |
| Desire Petroleum Limited | Salisbury | 1996 |
| Desla Group Limited | Wembley | 2022 |
| Dess Energy Limited | London | 2011 |
| Destiny Energy Limited | Belper | 2015 |
| Deusnet Limited | Ellesmere Port | 2025 |
| Deutschland Montreux Fertilizer Ltd | Cardiff | 2025 |
| Devenish Limited | Billericay | 1932 |
| Deveron Geoscience Associates Limited | Aberdeenshire | 1998 |
| Devine and Associates Glassmullagh Ltd. | Belfast | 2007 |
| Devine Sand & Gravel Limited | Omagh | 1995 |
| Devon and Cornwall Scrap Cars Ltd | Plymouth | 2021 |
| Devonian Scottish Fish Ltd | Orkney | 2019 |
| Dewality Consultants Limited | Exeter | 2012 |
| Dewsbury Sand & Gravel Ltd | Dewsbury | 2013 |
| DF Base Metals Limited | London | 2025 |
| DF Coordination Services Ltd | Montrose | 2025 |
| DG Access Ltd | Ossett | 2014 |
| DG Bond Limited | Billingham | 2021 |
| DG Pipefitting Ltd | Bishop Auckland | 2014 |
| Dg-Subsea Ltd | Aberdeen | 2014 |
| DGC OIL & GAS Ltd | Newark | 2020 |
| DGD Fabrications Ltd | St. Andrews | 2018 |
| DH Access Ltd | Peterhead | 2024 |
| DH Energy Solutions Ltd | Norwich | 2023 |
| DH Pipelines Limited | Torquay | 2023 |
| DH Subsea Services Ltd | Hebburn | 2026 |
| Dhinsa Healthcare Limited | Gillingham | 2019 |
| Diakrino Limited | London | 2017 |
| Diales Consult Limited | London | 1999 |
| Diales Group PLC | London | 1997 |
| Diamcorp Limited | Rickmansworth | 2024 |
| Diaminco Ltd | London | 2024 |
| Diamond Finance Limited | London | 2014 |
| Diamond Industries Limited | Manchester | 2020 |
| Diamond Offshore Limited | Altrincham | 1968 |
| Diamond OIL & GAS Limited | Kington | 2011 |
| Dibon Subsea Limited | Aberdeen | 2014 |
| Dickson Consultancy Services Ltd | Dundee | 2014 |
| Dicksons Hvac Ltd | Montrose | 2016 |
| DIG Africa Limited | Llanelli | 2024 |
| DIG International Group Limited | Llanelli | 2019 |
| Digital Geology Limited | Helensburgh | 1999 |
| Digswell Nurseries Limited | Welwyn | 2020 |
| Diligant NDT Ltd | Dunfermline | 2026 |
| Dilloway Aggregates Limited | Ingatestone | 2019 |
| Dilog Services Ltd | Aberdeen | 2019 |
| Dimbim Properties and Investment Ltd | Westhill | 2023 |
| Dinmore Aggregates Limited | Cheshire | 2016 |
| Direct Aggregate Supplies Limited | Cottingham | 2004 |
| Direct Diamond Products Limited | Sheffield | 2009 |
| Direct Geosolutions Ltd | London | 2026 |
| Dirtworks Limited | Armagh | 2007 |
| Discover Exploration Limited | London | 2012 |