| Crossmed Shipping Limited | Transport & logistics | 2004 |
| Crossroads Security Services Ltd | Administrative & support | 2025 |
| Crossview Commercial Ltd | Professional & scientific | 2025 |
| Crow Environmental Limited | Manufacturing | 2003 |
| Crowfield Airfield Ltd | Transport & logistics | 2020 |
| Crowflies Clothing Limited | Manufacturing | 2025 |
| Crown Gardens (Ufford) Limited | Administrative & support | 2019 |
| Crown Meadow (Stowupland) Management Company Limited | Real estate | 2021 |
| Crown Northcorp Limited | Financial services | 1997 |
| Crown Retailers Limited | Wholesale & retail | 2026 |
| CRS Personell Limited | Administrative & support | 2025 |
| CRS Ventures Limited | Professional & scientific | 2019 |
| Crs-Epos LLP | | 2025 |
| Crsenterprise Ltd | Information & communication | 2021 |
| CRU2 Ltd | Hospitality | 2024 |
| Crucis Designs Limited | Professional & scientific | 2010 |
| Crumble Fashion Ltd | Wholesale & retail | 2025 |
| Cryomation Limited | Other services | 2006 |
| Crystal Clean Ipswich Ltd | Administrative & support | 2025 |
| Crystal Martin Pension Scheme Trustees Limited | Financial services | 2024 |
| Crystal Rose Skin Clinic Ltd | Other services | 2017 |
| Crystal Specialists Solutions Ltd | Professional & scientific | 2017 |
| CS Ross Properties Ltd | Real estate | 2021 |
| CS UK Freight Ltd | Transport & logistics | 2026 |
| CS UK Logistics Ltd | Administrative & support | 2013 |
| Csclean Ltd | Administrative & support | 2025 |
| CSH Sport Ltd | Arts & recreation | 2024 |
| CSL Stan Ltd | Information & communication | 2023 |
| Csqs Services Ltd | Professional & scientific | 2024 |
| CSS Retail Ltd | Wholesale & retail | 2022 |
| CSW Electrical & Fire Ltd | Administrative & support | 2016 |
| CSW Landscape and Build Ltd | Construction | 2026 |
| CT Ipswich Limited | Construction | 2014 |
| CTC Productions Limited | Education | 2025 |
| CTC Worldwide Limited | Manufacturing | 2017 |
| Cteq Ltd. | Wholesale & retail | 2005 |
| CTM Tax Litigation Limited | Professional & scientific | 2015 |
| CTO Advisory Ltd | Information & communication | 2010 |
| Ctrj Global Limited | Professional & scientific | 2022 |
| Ctrlaltplayuk Ltd | Arts & recreation | 2026 |
| Ctromed Limited | Health & social care | 2024 |
| Ctruk Group Ltd | Financial services | 2008 |
| CTV Tranport Ltd | Transport & logistics | 2017 |
| Cube Square Properties Limited | Real estate | 2016 |
| Cuberoot Accounting Ltd | Professional & scientific | 2021 |
| Cuddloft Ltd | Wholesale & retail | 2024 |
| Cult 4X4 Ltd | Wholesale & retail | 2021 |
| Culturewise HR Consulting Ltd | Administrative & support | 2025 |
| Cumberland Mews (Woodbridge) Limited | Households | 1988 |
| Cupcake Cafe Ltd | Hospitality | 2020 |
| Cura Construction Limited | Construction | 2008 |
| Curaluxe Medical Ltd | Health & social care | 2026 |
| Curamus Consulting Ltd | Administrative & support | 2016 |
| Curated Cache Co Limited | Wholesale & retail | 2026 |
| Curioso Limited | Wholesale & retail | 2016 |
| Curious Curation Ltd | Wholesale & retail | 2020 |
| Curious Vitae Limited | Education | 2015 |
| Currenton Limited | Transport & logistics | 2025 |
| Curse & Omen Ltd | Information & communication | 2023 |
| Curtis Aerospace Limited | Transport & logistics | 2012 |
| Curzon ST Peter Limited | Construction | 2001 |
| Curzon ST. Peter Management Limited | Households | 2002 |
| Custella Ltd | Wholesale & retail | 2020 |
| Custom Power Tuning Ltd | Wholesale & retail | 2021 |
| Custom Recovery Services Limited | Transport & logistics | 2025 |
| Custom Storage Solutions Limited | Wholesale & retail | 2002 |
| Cute Wear Limited | Wholesale & retail | 2022 |
| Cutting Events Ltd | Administrative & support | 2023 |
| Cutting Homes Ltd | Households | 2026 |
| Cuygur's Ltd | Wholesale & retail | 2023 |
| CV Cleaning Ltd | Administrative & support | 2025 |
| CVC Property Limited | Real estate | 2023 |
| CW Fitness Ltd | Arts & recreation | 2018 |
| CW Wellness Hub Limited | Arts & recreation | 2024 |
| Cw-Computer-Solutions Ltd | Administrative & support | 2007 |
| Cwinners Ventures Ltd | Construction | 2023 |
| Cyan Broadcast Services Limited | Information & communication | 1995 |
| Cybrnet Limited | Information & communication | 2022 |
| Cycle Breaks Ltd | Administrative & support | 2021 |
| Cyfon Limited | Transport & logistics | 2015 |
| Cymatic Limited | Information & communication | 2011 |
| Cyril Fulcher Limited | Construction | 2003 |
| Cytex International Ltd | Financial services | 2025 |
| Czdigs Ltd | Real estate | 2026 |
| D & B Shipping Limited | Professional & scientific | 2000 |
| D & D AGA Maintenance Limited | Other services | 2010 |
| D & E Belstead Limited | Hospitality | 2025 |
| D & J H Homes Limited | Construction | 2014 |
| D & K Catering Ipswich Ltd | Hospitality | 2009 |
| D & K Transport Ltd | Transport & logistics | 2026 |
| D & M Smith Inns Ltd | Hospitality | 2018 |
| D & X Motors Ltd | Wholesale & retail | 2015 |
| D - T Trading Ltd | Other services | 2005 |
| D a B Associates Limited | Real estate | 2002 |
| D a B Construction (East Anglia) Ltd | Construction | 2007 |
| D a Designs (Suffolk) Ltd | Construction | 2023 |
| D a Formwork Ltd | Construction | 2018 |
| D and G Selby Limited | Financial services | 2013 |
| D and K Trailers Ltd | Wholesale & retail | 2025 |
| D B Events (GBR) Ltd | Arts & recreation | 2008 |