| Discovery Energy Limited | Whitland | 2002 |
| Discovery Geological Limited | Birkenhead | 2018 |
| Discovery Geoscience Ltd | Solihull | 2020 |
| Disko Exploration Limited | London | 2006 |
| DIT Measurement & Controls Ltd | London | 2007 |
| Divaan Consultancy Ltd | Harrow | 2024 |
| Divalo International Ltd | Ellesmere Port | 2023 |
| Dive Ahead Investments Ltd | London | 2025 |
| Diverse Energy Limited | Sunderland | 2017 |
| Diverse Engineering Solutions Limited | Inverurie | 2016 |
| Dixie Holding Suisse SA Ltd | London | 2025 |
| Dixon Geos Ltd | Swansea | 2009 |
| Dixon ROV Services Ltd | Market Harborough | 2017 |
| Dixstone UK Limited | London | 2017 |
| DJ Downie Ltd | Ellon | 2020 |
| DJ Insulation Ltd | Stockton-On-Tees | 2025 |
| DJB Slickline Services Limited | Callander | 2021 |
| DJD Access Ltd | Glenrothes | 2024 |
| DJG Services Ltd | Aberdeen | 2025 |
| DJH International Limited | Harwich | 2020 |
| DJL Resources Limited | Rotherham | 2017 |
| DK (Carew) Holdings Limited | Swansea | 2019 |
| DK Petroleum Limited | London | 2018 |
| DKG Services Ltd | Elgin | 2025 |
| DKH Logistics Limited | Stranraer | 2012 |
| DKK Rigging Services Limited | Blackpool | 2014 |
| DKS Diving Ltd | Durham | 2024 |
| DL Duddridge Ltd | Ashington | 2022 |
| DLJ Partners Ltd | Cambridge | 2004 |
| DLS Rigging Ltd | Darlington | 2018 |
| DM Contractors (North West) Limited | Ulverston | 2023 |
| DM Rose Ltd | Peterhead | 2025 |
| DM Smith Consultants Limited | Aberdeen | 2024 |
| DM Technical GAS Services Ltd | Hartlepool | 2023 |
| DMC Mining Services (UK) Ltd | Altrincham | 2017 |
| DMC PPS Ltd | Ashington | 2018 |
| DMC Rigging & Lifting Ltd | Peterhead | 2014 |
| Dmcc Services Limited | Elgin | 2025 |
| Dmcg Inspection Ltd. | Dalry | 2012 |
| DMD Drilling Limited | Elgin | 2022 |
| DMD Well Services Ltd | Farnell | 2011 |
| DME Global Limited | London | 2025 |
| DMF Engineering Machining Ltd | Aberdeen | 2019 |
| DMH Subsea Services Ltd | Peterhead | 2018 |
| DMK Solutions Ltd | Bradninch | 2009 |
| DMK Well Engineering Services Ltd | Copthorne | 2013 |
| DML MS Ltd | Banff | 2022 |
| DMM Quarry Services Limited | Braintree | 2014 |
| DMP Holdings Limited | Coventry | 2023 |
| DMS Quarry and Mining Service Limited | London | 2021 |
| DMT Consulting Limited | Nottingham | 1947 |
| Dmts International UK Ltd | London | 2024 |
| DNI Mining Shareholders Ltd | Leicester | 2012 |
| DNO Exploration UK Limited | Aberdeen | 2014 |
| DNO North Sea (Rogb) Limited | Leeds | 1984 |
| DNO North Sea (U.K.) Limited | Leeds | 2003 |
| DNO North Sea Limited | Leeds | 2002 |
| DNO UK Limited | Leeds | 2005 |
| DOA Exploration Limited | Warminster | 2009 |
| Dogbone Limited | Dunblane | 2018 |
| Dolphin Drilling Limited | Eastleigh | 1971 |
| Dolphin Drilling Offshore Limited | Eastleigh | 2020 |
| Dolphin Offshore Services Ltd | London | 2026 |
| Domaine DU LAC Ltd. | Norwich | 2010 |
| Dome Petroleum Resources Ltd | Surbiton | 2005 |
| Dominic Atkin Services Limited | Newark | 2016 |
| DON Valley Materials Handling Limited | Doncaster | 2020 |
| Donald Solutions Ltd | Kirriemuir | 2025 |
| Dontruck&Son Limited | Spalding | 2013 |
| Doodle Engineering Limited | Blackpool | 2009 |
| Dookandubh Limited | Alford | 2007 |
| Dorebar Limited | Isleworth | 2024 |
| Dorfner Anzaplan UK Limited | Norwich | 2023 |
| Dorset Stone Company Limited | Sturminster Newton | 2003 |
| Doucar Ltd | Turriff | 2012 |
| Doulting Stone Quarry Limited | Shepton Mallet | 2018 |
| Dove Offshore Services Ltd | Jarrow | 2019 |
| Dover Holdings UK Ltd | London | 2025 |
| Doveshill Mineral Resources Ltd | Bournemouth | 2021 |
| Dowdell Mining Limited | Newquay | 2013 |
| Downhole Fluid Solutions Limited | Motherwell | 2004 |
| Downhole Products Limited | Edinburgh | 1993 |
| Downhole Tools International Limited | Poole | 2009 |
| DPD Services Ltd | Newcastle Upon Tyne | 2016 |
| DPM Access Solutions Limited | Blackpool | 2013 |
| DPM BH Holdings Limited | London | 2017 |
| Dpmetals Services (UK) Limited | London | 1999 |
| DRA International Limited | London | 2002 |
| DRA Projects Europe Limited | London | 2024 |
| Draco Engineering Solutions Limited | Brighouse | 2023 |
| Draeth Developments Limited | London | 1995 |
| Dragon & Eagle Holdings Ltd | Cardiff | 2018 |
| Dragon Drilling (Landfill) Limited | Corwen | 2013 |
| Dragon Drilling Limited | Corwen | 2005 |
| Dragon OIL & GAS Limited | London | 2026 |
| Dragon Subsea Ltd | Llandudno Junction | 2009 |
| Dragonfly Access Limited | Cockermouth | 2023 |
| Dragonträull Fuels Ltd | Cullompton | 2022 |
| Drakelands Restoration Limited | Plympton | 2019 |
| Draupner Energy Limited | London | 2016 |