| D3LTA Energy Ltd | Richmond | 2026 |
| D7 NIT Ltd | London | 2025 |
| DA Electrician Ltd | West Bromwich | 2023 |
| DA Renewables Limited | Castlewellan | 2014 |
| DA Solar Ltd | Leighton Buzzrd | 2020 |
| Da&Ab Limited | Aldershot | 2025 |
| Dabih Solar Ltd | Bristol | 2020 |
| DAD Contract Services Ltd | Cambridge | 2021 |
| Daddicool Limited | Bexley | 2015 |
| Daedalus Acquisitions Limited | Reading | 2016 |
| Daedalus Midco 2 Limited | Reading | 2016 |
| Daedalus Midco Limited | Reading | 2016 |
| Daedalus Topco Limited | Reading | 2016 |
| Dafen Power Limited | Cardiff | 2012 |
| Dafen Reserve Power Limited | Bristol | 2014 |
| Daffodil Energy Supply Limited | London | 2017 |
| Dagenham Wind Park Limited | Stroud | 1998 |
| Dahu Energy Limited | St. Ives | 2026 |
| Dahu Group Limited | Ruislip, | 2025 |
| Daikin Airconditioning UK Limited | Weybridge | 2002 |
| Daines Bess Limited | Cheltenham | 2022 |
| Daines Energy Park Limited | London | 2022 |
| Daines Flexpower Ltd | Cheltenham | 2024 |
| Daintree Wind Farm Limited | Warrington | 2011 |
| Dairy House Solar Limited | London | 2014 |
| Dais Energy Germany Limited | London | 2024 |
| Dais Energy Limited | London | 2023 |
| Dais Energy Management Services Limited | London | 2024 |
| Dais Energy Ventures Limited | London | 2023 |
| Daisy Bank Farm Enterprises Ltd | Stoke On Trent | 1992 |
| Daisy Electrics Limited | Newport | 2026 |
| Daisy Hill Renewable Energy Limited | Reading | 2023 |
| Daisy NO 1 Limited | London | 2013 |
| Daisy Project Services Limited | Stockton On Tees | 2018 |
| Dalby Energy Limited | London | 2023 |
| Dalectronics Limited | Brentwood | 2015 |
| Daleriver Limited | Newry | 2017 |
| Dalia Holdings Ltd | London | 2019 |
| Daligas Limited | Northampton | 2012 |
| Dalipower Limited | London | 2018 |
| Dallas Windfarm Limited | Edinburgh | 2018 |
| Dalmarnock Bess Ltd | London | 2020 |
| Dalrada Home Ltd | Bathgate | 2024 |
| Dalriada Renewables Limited | London | 2021 |
| Dalry Community Wind Company Limited | Edinburgh | 2004 |
| Dalry Community Wind Farm Limited | Edinburgh | 2010 |
| Dalswinton Windfarm (Scotland) Limited | Edinburgh | 2005 |
| Daltaic Ltd | Dereham | 2025 |
| Dalzell (Newarthill) Limited | Edinburgh | 2023 |
| Damac Energy Limited | Aberdeen | 2012 |
| Damsongreen Energyfarm Limited | Houghton Le Spring | 2024 |
| Damvent (UK) Limited | London | 2016 |
| DAN Bolton Electrical Limited | Stockport | 2007 |
| Dands Power Ltd | Malton | 2024 |
| Daneglans Hydro Limited | Belper | 2018 |
| Daneriver Hydropower Services Limited | Ascot | 2014 |
| Dansco Utilities Limited | Bridgend | 2018 |
| Darcy Climate Services Ltd | Kidderminster | 2022 |
| Dargan Road Biogas Limited | Belfast | 2017 |
| Darios Solution Ltd | London | 2025 |
| Darlees Wind Farm Limited | Maidenhead | 2022 |
| Darlington Solar 1 Limited | London | 2021 |
| Darren Williams Electrics UK Limited | Selby | 2016 |
| Darrenold Electrical Ltd | Exeter | 2017 |
| Darroch Power Limited | London | 2014 |
| Dart Leader Limited | Edinburgh | 2023 |
| Dart Renewables Ltd | Dartington | 2009 |
| Dartford Green Power Ltd | Ross On Wye | 2021 |
| DAT HV Mechanical Electrical Fitting Ltd | Hull | 2016 |
| Dataprosupport Limited | Reading | 2016 |
| Datk Limited | Cumnock | 2018 |
| Datum Design and Build Limited | Ringwood | 2017 |
| Datum HV Limited | London | 2026 |
| Dave Duffy GAS Services Ltd | Stoke On Trent | 2013 |
| David Bliss Limited | Feltham | 2023 |
| David Bravo Engineering Limited | London | 2019 |
| David Prior H V Electricals Ltd | Newcastle Upon Tyne | 2017 |
| David Smith Offshore Ltd | Kilmarnock | 2022 |
| David Thomas Offshore Services Limited | Stockton-On-Tees | 2019 |
| Davies Energy Ltd | Fishguard | 2015 |
| Davies Renewable Energy Limited | Pontypridd | 2020 |
| Davinci Photovoltaic Limited | Belfast | 2020 |
| Dawes Electricians Ltd | Exeter | 1983 |
| Dawnay Solar Farm Limited | London | 2025 |
| Dayfields Solar Limited | Gatwick | 2011 |
| Daymz Limited | Bristol | 2016 |
| DB Capital Solutions Limited | Ware | 2013 |
| DB Controls Ltd | Essex | 2024 |
| DBA Ofto Holdco Limited | London | 2024 |
| DBA Ofto Limited | London | 2024 |
| DBA Ofto Project Limited | London | 2024 |
| DBH Electrical Ltd | Lytham St. Annes | 2021 |
| DBS 1 Limited | London | 2020 |
| DBS Marketing Limited | London | 2020 |
| DBS Mechanical & Electrical Ltd | Watford | 2013 |
| DC Air Conditioning Ltd | Otley | 2017 |
| DC Juice Limited | London | 2025 |
| DC21 (Group) Limited | Huddersfield | 2012 |
| DC21 Earth SPV Limited | Manchester | 2013 |
| DC21 Limited | Huddersfield | 2009 |