| DC21 Mars SPV Limited | Huddersfield | 2015 |
| DC21 Mercury SPV Limited | Harrogate | 2012 |
| DC21 Venus SPV Limited | Huddersfield | 2013 |
| Dcadla Solutions Ltd | Tonbridge | 2021 |
| DCH Air Conditioning and Electrical Limited | Pershore | 2019 |
| DCK Offshore Limited | Grimsby | 2024 |
| DCM Cooling Limited | Belfast | 2021 |
| DCR Jointing Limited | Wishaw | 2023 |
| DCS (Electrical & Data) Limited | Huddersfield | 2012 |
| Dcutilities NE Limited | Bishop Auckland | 2022 |
| DD Electrical Services Ltd | Bexleyheath | 2015 |
| DD Power Ltd | Ruislip, | 2025 |
| Ddsl Electric Limited | Southampton | 2014 |
| DE 001 Limited | London | 2023 |
| DE 002 Limited | London | 2023 |
| DE 003 Limited | London | 2023 |
| DE 004 Limited | London | 2023 |
| DE 005 Limited | London | 2023 |
| DE Utilities Limited | Durham | 2025 |
| Dealanach Limited | Motherwell | 2020 |
| Dean Bottom Farm Solar Limited | London | 2023 |
| Dean Farm Solar Developments Limited | Norwich | 2022 |
| Dean Snell Electrician Ltd | Leigh-On-Sea | 2019 |
| Deanston Stima Limited | Edinburgh | 2012 |
| Debdale Hill Limited | Notts | 2012 |
| Debdale Solar Limited | London | 2015 |
| DEC Electrical Ltd | Solihull | 2019 |
| Decarbonisation Solutions Ltd | Lincoln | 2024 |
| Decarbonise Fuel Limited | Guildford | 2020 |
| Decent Energy Ltd | Tonbridge | 2023 |
| Decisive Security Ltd | Stevenage | 2024 |
| Decon Contracting Ltd | Greenford | 2013 |
| Decon Electrical Systems Limited | Birmingham | 2015 |
| Decoy Farm Power Limited | Wellingborough | 2014 |
| Decoy Solar Farm 3 Limited | Colchester | 2024 |
| DEE CEE Electrical Ltd | Prestwick | 2022 |
| Deep Geothermal Power Limited | Orkney | 2021 |
| Deepbridge Renewable Energy (1) Limited | Chester | 2013 |
| Deepbridge Renewable Energy (2) Limited | Chester | 2014 |
| Deepdale Farm Solar Ltd | London | 2013 |
| Deepmore Energy Centre Limited | Norwich | 2021 |
| Deepseek Software Ltd | Bath | 2008 |
| Deer Park Energy Ltd | Truro | 2016 |
| Deerdykes Bioenergy Limited | London | 2025 |
| Deerpark Wind Ltd | Ballymena | 2014 |
| Deeside Power Operations Limited | Hull | 2020 |
| Deeside Solar Farm Limited | London | 2014 |
| Deeside SPV Ltd | London | 2023 |
| Deeves Hall Renewable Energy Limited | Reading | 2024 |
| DEF Solar Panels Ltd | Pontypridd | 2020 |
| Definitive Electrical Limited | Hungerford | 2020 |
| Dehughes Limited | Brentwood | 2014 |
| Delabole Windfarm Limited | Bristol | 2009 |
| Delamore Renewables Limited | Shepton Mallet | 2025 |
| Dell Electrics Ltd | Taunton | 2023 |
| Dell Renewables Limited | Grays | 2020 |
| Dell Wind Farm Limited | Maidenhead | 2014 |
| Dellian Ltd | Lydd | 2015 |
| Dellpoint Pyramid Global Marketing Limited | London | 2017 |
| Delphic Computer Services Limited | Herefordshire | 1991 |
| Delt Installations Limited | Braintree | 2015 |
| Delta Chiller Services Ltd | High Wycombe | 2024 |
| Delta GAS and Power Limited | Watford | 2023 |
| Delta Mechanical Services Ltd | Poole | 2026 |
| Delta Power Networks Ltd | Cramlington | 2023 |
| Delta Umbra Limited | Morpeth | 2020 |
| Deltaview Limited | Stewarton | 2004 |
| Deltec Plumbing and Heating Ltd | Witney | 2014 |
| Demontfort Elements Limited | Hitchin | 2008 |
| DEN Brook Energy Limited | Leeds | 2012 |
| Dengie Solar Park Limited | Shepton Mallet | 2022 |
| Deniss Solutions Ltd | Northampton | 2026 |
| Denmoss Wind Limited | Glasgow | 2015 |
| Dens Energy UK Ltd | St. Albans | 2026 |
| Denton Wharf Marine Services Limited | Carlisle | 2024 |
| Dents Hall Battery Storage Limited | Stonehouse | 2022 |
| Denuo Ltd | Glossop | 2023 |
| DEP Duxford 2 Ltd | Ashford | 2017 |
| DEP Gorsehall Ltd | Ashford | 2017 |
| DEP HWC Ltd | Ashford | 2017 |
| DEP IA1 Ltd | Ascot | 2017 |
| DEP Trading Company Ltd | Ashford | 2017 |
| Derby Solar Ltd | Mansfield | 2026 |
| Derbyshire Air Conditioning Ltd | Belper | 2025 |
| Derril Renewables Limited | Holsworthy | 2024 |
| Derril Water Solar Limited | Redruth | 2016 |
| Derrymore Energy Ltd | Newry | 2024 |
| Derrynanny Wind Ltd | Belfast | 2021 |
| Derwent Hydro Holdings Limited | Matlock Bath | 2024 |
| Derwent Hydroelectric Power Limited | Matlock Bath | 1988 |
| Derwent London AD Limited | London | 2021 |
| Derwent London Green Energy Limited | London | 2020 |
| Derwent Power Limited | Newtown | 2014 |
| Derwent Renewable Power Limited | Newtown | 2015 |
| Derwent Solar 2 Limited | Bath | 2021 |
| Derwent Valley Projects Limited | Cockermouth | 2023 |
| Derwenthaugh Organics Ltd | East Yorkshire, Beverley | 2021 |
| Derwin Fawr Renewables Ltd | Porthmadog | 2016 |
| Desair Ltd | Keighley | 2025 |
| Desborough Solar and Battery Storage II Limited | Cheltenham | 2023 |