| Crown Holdings NE Limited | Financial services | 2026 |
| CRS Security Ltd | Administrative & support | 2025 |
| Crusader Conservatories Limited | | 1983 |
| Crust K Limited | Hospitality | 2026 |
| Crust Norton Limited | Hospitality | 2024 |
| Crustyzz Ltd | Hospitality | 2025 |
| Cryptic Realms Ltd | Information & communication | 2023 |
| Crystal Clean House Keeping Ltd | Administrative & support | 2024 |
| Crystal Maids Commercial Cleaning Ltd | Administrative & support | 2023 |
| Crystalquill Innovations Limited | Professional & scientific | 2024 |
| CS Autos Teesside Ltd | Wholesale & retail | 2024 |
| Csaom Design Services Ltd | Professional & scientific | 2023 |
| CSM Offshore Ltd | Professional & scientific | 2022 |
| Csmp Financials Ltd | Professional & scientific | 2023 |
| CSP Electrical Services Ltd | Construction | 2014 |
| CSP Wind Services Ltd | Manufacturing | 2023 |
| CST Plumbing & Heating Ltd | Construction | 2024 |
| CT Motorkraft Limited | Wholesale & retail | 2017 |
| CT Visual Limited | Professional & scientific | 2014 |
| CTS Northern Parking Ltd | Administrative & support | 2011 |
| CTS Northern Properties Ltd | Real estate | 2018 |
| Cube Media Group Ltd | Information & communication | 2019 |
| Cubiculaeum Ltd. | Real estate | 2024 |
| Cubix Software Limited | Information & communication | 2005 |
| Cult Foods Ltd | Wholesale & retail | 2024 |
| Cultivate Tees Valley C.I.C. | Agriculture & fishing | 2018 |
| Cumberland 1958 Limited | Extraterritorial | 2015 |
| Cumby Projects Ltd | Professional & scientific | 2021 |
| Cure Clinic Ltd | Wholesale & retail | 2026 |
| Curlgrange Ltd | Other services | 2024 |
| CUT Above Sedgefield Limited | Other services | 2015 |
| Cutsonwheels Ltd | Other services | 2025 |
| Cutting Edge Grounds Maintenance Ltd | Agriculture & fishing | 2021 |
| Cvexportdirect Limited | Wholesale & retail | 2016 |
| CWH Construction Ltd | Construction | 2021 |
| Cyber Initiative Ltd | Information & communication | 2018 |
| Cyberfirst Limited | Extraterritorial | 2000 |
| Cygnet Access Solutions Ltd | Professional & scientific | 2011 |
| D & H Global Services Ltd | Health & social care | 2015 |
| D a Bunce Civil Engineering Ltd | Construction | 2003 |
| D Boyce Building Services Ltd | Construction | 2016 |
| D Cahill Inspection Limited | Construction | 2014 |
| D Coleman Holdings Ltd | Financial services | 2025 |
| D Holley Process Services Ltd | Mining & quarrying | 2018 |
| D Johnson Mechanical Services Ltd | Professional & scientific | 2019 |
| D K Electrix Ltd | Construction | 2014 |
| D L Grant Ltd | Construction | 2012 |
| D P Chadwick & Co Ltd | Hospitality | 2015 |
| D T a Consulting Engineers LLP | | 2004 |
| D&Ck Ltd | Extraterritorial | 2020 |
| D&D Global Ltd | Hospitality | 2025 |
| D' Pokus Ltd | Wholesale & retail | 2023 |
| D. O'Brien Plumbing Ltd | Construction | 2014 |
| D.I.T. Transport Limited | Transport & logistics | 2017 |
| D.J.R. Holdings Limited | Professional & scientific | 1997 |
| D.J.R. Smith Limited | Construction | 1993 |
| D.J.R. Smith Properties Limited | Real estate | 2026 |
| D.Mclaughlin Inspection Services Ltd | Professional & scientific | 2023 |
| D.S.S Driver Solutions Limited | Transport & logistics | 2012 |
| DA Components Ltd | Manufacturing | 2016 |
| DA Vinci House Freehold Limited | Households | 2008 |
| Dabb Window Cleaning Ltd | Administrative & support | 2022 |
| Dabico Airport Solutions UK Limited | Manufacturing | 1986 |
| Dadda Memorial Limited | Health & social care | 2022 |
| Dads Medical Services Ltd | Health & social care | 2024 |
| Daftify Fusion Limited | Manufacturing | 2024 |
| Dagv Ltd | Professional & scientific | 2022 |
| Dagv Property Ltd | Real estate | 2022 |
| DAH 001 Limited | Real estate | 2025 |
| DAH 002 Limited | Real estate | 2025 |
| DAH 003 Limited | Real estate | 2025 |
| DAH 004 Limited | Real estate | 2026 |
| DAH 005 Limited | Real estate | 2026 |
| Daintydoodles Ltd | Wholesale & retail | 2025 |
| Daisy Woodhouse Hair Limited | Other services | 2018 |
| Dalkin Recruitment Ltd | Administrative & support | 2025 |
| Dalveen House Ltd | Agriculture & fishing | 2025 |
| DAN1 Logistics Limited | Transport & logistics | 2023 |
| Dana Electrical Ltd | Construction | 2025 |
| Daniel Barron Design Limited | Professional & scientific | 2010 |
| Daniel John Wind & Offshore Services Ltd | Construction | 2026 |
| Daniel Sigsworth Solar & Construction Ltd | Construction | 2025 |
| Danish Rizwan Logistics Ltd | Transport & logistics | 2025 |
| Danish Saboor Ltd | Wholesale & retail | 2025 |
| Danniel Spooner Financial Management Ltd | Professional & scientific | 2023 |
| Danny Plumbing and Heating Ltd | Construction | 2026 |
| Danpec Consulting Ltd | Wholesale & retail | 2024 |
| Danyal Property Ltd | Real estate | 2023 |
| DAR Lettings Ltd | Real estate | 2021 |
| Darhar Limited | Households | 2025 |
| Darkmind Ltd | Professional & scientific | 2025 |
| Darlington Garden Village Limited | Real estate | 2020 |
| Darlington Memorials Ltd | Manufacturing | 2025 |
| Darlington Tyre & Auto Centre Limited | Wholesale & retail | 2009 |
| Darnton & Co Limited | Administrative & support | 2014 |
| Daro-Allam Ltd | Health & social care | 2023 |
| Dart Property Management Ltd | Real estate | 2018 |
| DAS Transport Compliance Ltd | Transport & logistics | 2025 |
| Datahaven Consulting Limited | Information & communication | 1998 |
| Date JAM Ltd | Administrative & support | 2024 |