| DIS Sprinklers Limited | Cheltenham | 1905 |
| Disability Positive | Northwich | 2000 |
| Discover Aesthetic Doctors Limited | Burnley | 2021 |
| Discovery Care Group Holdings Ltd | London | 2023 |
| Discovery Homecare Dundee Limited | Dundee | 2024 |
| Discus Fire Protection Limited | Brentwood | 2026 |
| Distinguish Sisters Limited Limited | London | 2025 |
| Diva Fire Ltd | London | 2025 |
| Diversicare Supported Living Limited | Nelson | 2024 |
| Diversity Hub Ltd | Wokingham | 2025 |
| Diversity Social Care Ltd | Leicester | 2018 |
| Diversity Solutions Limited | Cardiff | 2022 |
| Divert 2 Change CIC | London | 2019 |
| Divest Consortium Ltd | London | 2025 |
| Divetimaging Ltd | St. Albans | 2023 |
| Divide and Conquer Limited | Huddersfield | 2025 |
| Divine Chisom Healthcare Limited | Wolverhampton | 2023 |
| Divine Dynamics Limited | Derby | 2025 |
| Divine General Services Ltd | Wolverhampton | 2021 |
| Divine Healthkare Solutions Ltd | Barnsley | 2022 |
| Divine Recovery Ltd | Crawley | 2021 |
| Divine Sight Ltd | Glasgow | 2022 |
| Divinedes Ltd | Barking | 2018 |
| Divinity Group Limited | London | 2024 |
| Divinity Homecare Ltd | Enfield | 2024 |
| Divinity Services Ltd | Walsall | 2018 |
| Divrich Limited | Wellingborough | 2026 |
| DJ Fire Solutions Limited | Ebbw Vale | 2025 |
| DJ Shepherd & Associates Ltd | York | 2023 |
| DJB Physiotherapy Ltd | Sutton Coldfield | 2024 |
| DJC Playground Inspections Limited | Northampton | 2020 |
| Djed Services Limited | Hull | 2025 |
| Djjintensity Ltd | Newtownabbey | 2022 |
| DJL Fire Safety Consultancy Limited | Buckingham | 2022 |
| DJM Consult Limited | Derby | 2019 |
| DJT Sprinklers Ltd | Welling | 2025 |
| DKA (Dick Koelling Associates) Limited | Leicester | 2021 |
| Dkpn Limited | Glasgow | 2023 |
| DL Administrative Services Limited | Cwmbran | 2019 |
| DL Changes Ltd | Halifax | 2025 |
| Dlbsafetyconsultancy Ltd | Middlesbrough | 2026 |
| DLR Care Ltd | Southport | 2019 |
| DM Functionals Ltd | Croydon | 2022 |
| DM Hutson Services Limited | Cardiff | 2013 |
| DMB TM Ltd | Doncaster | 2025 |
| DMC (Dhaka Medical College) Alumni Club UK Ltd | London | 2024 |
| DMC Fire Risk Management Ltd | Kirkcaldy | 2020 |
| DMK Imaging Ltd | London | 2020 |
| DMO Fire Safety Ltd | Nottingham | 2022 |
| DMR Fire Ltd | Northfield | 2023 |
| Dmrt Consulting Limited | Leicester | 2023 |
| DMT Healthcare Ltd | Chester | 2025 |
| DNA Fire Engineering Limited | Essex | 2026 |
| DNA Staffing Solutions Limited | Cheltenham | 2020 |
| Dnmpf Ltd | Nottingham | 2024 |
| DNP Education Limited | Wellingborough | 2026 |
| DOC Check AI Limited | London | 2025 |
| Doctors and Lawyers for Responsible Medicine | London | 1992 |
| Dogs Against Drugs (in Memory of John) | Lerwick | 2003 |
| Dolmans Fire Safety Ltd | Burton-On-Trent | 2025 |
| Domdiv Limited | Gravesend | 2024 |
| Domelec Training Services Ltd | Bedworth | 2016 |
| Domestic Sprinklers Devon and Somerset Limited | Wellington | 2013 |
| Domestic Sprinklers Dorset Limited | Portland | 2013 |
| Domestic Sprinklers Hampshire Limited | Weymouth | 2013 |
| Domestic Sprinklers Ltd | Portland | 2000 |
| Domestic Sprinklers West Midlands Limited | West Bromwich | 2013 |
| Domestic Sprinklers West Sussex Limited | Weymouth | 2013 |
| Domiciliary Physiotherapy Care UK Ltd | Atherstone | 2023 |
| Dominion Support 24/7 Limited | Manchester | 2026 |
| Donaldsona Consulting Ltd | Lymington | 2024 |
| Donimero Recruitment Ltd | Cardiff | 2020 |
| Don’T Shoot the Messenger Ltd | Swadlincote | 2022 |
| Doona Project Management Limited | London | 2014 |
| Door Check Fire Door Inspections Ltd | Wallasey | 2022 |
| Door Data Systems Ltd | Droitwich | 2020 |
| Doors 4 Inspection Limited | Brentwood | 2025 |
| Doorway to Belonging Ltd | Rainham | 2022 |
| Dopamind Wellness & Performance Ltd | Harrogate | 2025 |
| Dorman & Co (Law Enforcement Agents) Limited | Harrow | 2006 |
| Dorset & Devon Fire Solutions South West Ltd | Weymouth | 2015 |
| Dorset Fire Doors Ltd | Weymouth | 2025 |
| Dorset Health and Safety Limited | Weymouth | 2014 |
| Double SS Divine Healthcare Services Ltd | Liverpool | 2020 |
| Double Watch Security Services Ltd | London | 2025 |
| Dove Integral Ltd | London | 2021 |
| Dovetail Fire Doors Ltd | Newton Abbot | 2025 |
| Downard Health Ltd | London | 2026 |
| Downham Market Christmas Lights Limited | Downham Market | 2016 |
| Downshire Homes Limited | Cheltenham | 2015 |
| Doxiacare Limited | Blackburn | 2021 |
| DPG Inspection Services Ltd | Birmingham | 2025 |
| DPH Fire Protection Ltd | Leigh-On-Sea | 2022 |
| DPI Healthcare Ltd | Walsall | 2015 |
| DPJ Passive Fire Protection Limited | Battlesbridge | 2024 |
| DPL Fire Protection Limited | Manchester | 2009 |
| DR Abbot Health Care Ltd | Dudley | 2023 |
| DR Arora Health Limited | Hornchurch | 2025 |
| DR Claire Pugh Ltd | Bath | 2024 |
| DR Courtnie Beesley-Gibson ND Assessment Ltd | Bedale | 2025 |