| Cart 2 Door Ltd | Ammanford | 2025 |
| Carter Operations Ltd | Denny | 2025 |
| Carters Waste Management Limited | Hertfordshire | 2019 |
| Cartigo Ltd | Waltham Abbey | 2020 |
| Cartiwaste Ltd | Waltham Abbey | 2021 |
| Cartmel Mineral Water Limited | Grange-Over-Sands | 2013 |
| Cartridge Recycling UK Limited | Bedford | 2019 |
| Carvetii Services Limited | Carlisle | 2021 |
| CAS Metals Ltd | Macclesfield | 2025 |
| Cascade Water Products Limited | Dundee | 2015 |
| Casey Limited | Wirral | 2008 |
| Caso Reactors Ltd | London | 2024 |
| Cason & Bazley Pipeline Servicing Ltd | Felthorpe | 2024 |
| Cassidy's MOT Limited | Manchester | 2004 |
| Castell Clyd Ltd | Bridgend | 2025 |
| Castiell Limited | Harrow | 2018 |
| Castle Acre (Framlingham) Management Company Limited | Woodbridge | 2011 |
| Castle Bolton Water Company Ltd | Leyburn | 2013 |
| Castle Builders Kent Ltd | Canterbury | 2024 |
| Castle Fifteen Consulting Ltd | Matlock | 2020 |
| Castle Healthcare Supplies Ltd | Bridlington | 2011 |
| Castle Nibole Limited | Hereford | 2009 |
| Castle Oils Limited | Ilkeston | 1983 |
| Castle Quay Metal Recyclers Limited | Pembroke | 2014 |
| Castle Skip Hire & Groundworks Limited | Bilston | 2005 |
| Castle Timber Recycling Limited | Ballymena | 2015 |
| Castle Waste Services Limited | Ilkeston | 1978 |
| Castle Water (Scotland) NO.2 Limited | Blairgowrie | 2015 |
| Castle Water Group Limited | Blairgowrie | 2022 |
| Castle Water Limited | Blairgowrie | 2014 |
| Castle Water Networks Limited | Blairgowrie | 2022 |
| Castlebrook Gardens Limited | Presteigne | 2001 |
| Castlefort Group Ltd | Newry | 2009 |
| Castlehill Damage Restoration Ltd | Sheffield | 2021 |
| Castles Shredding Limited | Deal | 2014 |
| Cata & ALY Ltd | Swadlincote | 2025 |
| Catalyst Hygiene Ltd | Sale | 2025 |
| Catalytic Recycling UK Ltd | Nottingham | 2015 |
| Catch U Drainage Solutions Ltd | Uxbridge | 2024 |
| Catchment Moray Limited | Edinburgh | 2000 |
| Catchment TAY Holdings Limited | Edinburgh | 1998 |
| Catchment TAY Limited | Edinburgh | 1998 |
| Catcon UK Ltd | Goole | 2021 |
| Cater Oils Ltd | Addlestone | 2013 |
| Catplant Quarry Limited | Barnsley | 1999 |
| Caulmert Limited | Bangor | 2008 |
| Causeway Recycling Ltd | Belfast | 2025 |
| Causeway Waste Limited | Antrim | 2021 |
| Causeway Water Solutions Ltd | Belfast | 2016 |
| Cavity Installation & Removal (UK) Ltd | Blackpool | 2019 |
| Cawston Slurry Disposal Limited | Norwich | 1985 |
| Cayres and Sons Ltd | Harlow | 2024 |
| Cayser Water Systems Ltd | Maidstone | 2026 |
| CB Drainage Ltd | Blackwood | 2026 |
| CB One Solution Ltd | Stevenage | 2016 |
| CB Technical Services (UK) Ltd | Burnley | 2007 |
| CB Waste and Recycling Ltd | Norwich | 2010 |
| CBC Maintenance Services Ltd | Ongar | 2011 |
| Cbconstruction London Limited | London | 2020 |
| CBH Environmental Ltd | Carlisle | 2018 |
| CBS Recycling Ltd | London | 2020 |
| CBW Clearances Ltd | Ongar | 2020 |
| Ccandco Ltd | London | 2020 |
| CCL Waste Clearance Ltd | Romford | 2026 |
| CCM (Desford) Limited | Leicester | 2012 |
| CCR Energy Limited | Barry | 2022 |
| CCR Waste and Removals Limited | Liverpool | 2025 |
| CCS Services Group Ltd | Leigh-On-Sea | 2024 |
| CCS Waste Management Limited | London | 2024 |
| Cctv Drain Surveys Ltd | Sheffield | 2012 |
| CCV Ground Works Ltd | South Ockendon | 2023 |
| CD Servicing Limited | London | 2001 |
| CD Solutions North West Limited | Northampton | 2014 |
| CDC Draincare (East Midlands) Limited | Leeds | 2021 |
| CDC Draincare (Manchester) Limited | Leeds | 2022 |
| CDC Draincare (West Midlands) Limited | Leeds | 2022 |
| CDC Waste Management Ltd | Ilford | 2023 |
| CDF Clearance and Waste Removal Ltd | Rochdale | 2025 |
| CDK Haulage Ltd | Manchester | 2025 |
| CDL Core Ltd | Preston | 2026 |
| CDM Nottingham Limited | Nottingham | 2009 |
| Cdrains Ltd | London | 2020 |
| CDS Collection and Trading Ltd | Birmingham | 2010 |
| CDS Leak Resolve Ltd | Bristol | 2026 |
| CDS Rose Limited | Tunbridge Wells | 2009 |
| CDS Services Ltd | Sidcup | 2021 |
| Ceah (Hydro) Limited | London | 2013 |
| Ceased Trading 07075608 Ltd | London | 2009 |
| Cedek Water Treatment Ltd | Torrington | 2014 |
| Cedits Ltd. | Northampton | 2011 |
| CEE Squared Waste Removal Ltd | Dumbarton | 2026 |
| Cello Recycling Ltd | Derby | 2013 |
| Cellsafeuk Ltd | Willenhall | 2024 |
| Celtic Recycling Ltd. | Pyle | 1992 |
| Celtic Vacuum Limited | Tenby | 1993 |
| Celtic Waste Limited | Aberystwyth | 2022 |
| CEM Plumbing Limited | London | 2021 |
| Cema Commercial Ltd. | Nottingham | 1985 |
| Cenco Ltd | Dunmow | 2020 |
| Center for Regenerative Design and Collaboration (Crdc UK) UK Limited | London | 2020 |