| Taylor Wimpey | Taylor Wimpey PLC | construction and engineering | water pollution violation | 2023 | £488,772 |
| Persimmon Homes Limited | Persimmon PLC | construction and engineering | water pollution violation | 2022 | £433,161 |
| Dwr Cymru Welsh Water | Dwr Cymru Cyfyngedig (Welsh Water) | utilities and power generation | water pollution violation | 2021 | £205,872 |
| Tongfang Global (UK) Co Limited | | | hazardous waste violation | 2018 | £160,760 |
| GLJ Recycling Ltd | | | Environmental Violation | 2022 | £94,294 |
| Trade Effluent Services Limited | | | Environmental Violation | 2017 | £83,900 |
| Archimica Chemicals Ltd | | | Environmental Violation | 2013 | £80,000 |
| UPM | UPM | paper and packaging | Environmental Violation | 2017 | £78,000 |
| DBC Site Services 2005 Ltd | | | Environmental Violation | 2021 | £75,411 |
| Euro Garages Ltd | EG Group | retailing | Environmental Violation | 2017 | £65,044 |
| Parry & Evans Recycling Services Ltd | | | Environmental Violation | 2017 | £58,000 |
| Tower Regeneration Limited | | | water pollution violation | 2021 | £56,781 |
| Sundorne Products (Llanidloes) Ltd | | | Environmental Violation | 2019 | £55,400 |
| Edenstone Homes Limited | | | water pollution violation | 2024 | £54,762 |
| Dwr Cymru Welsh Water | Dwr Cymru Cyfyngedig (Welsh Water) | utilities and power generation | water pollution violation | 2019 | £49,151 |
| Ammanford Recycling Limited | | | environmental violation | 2024 | £48,652 |
| GP Biotec Ltd | | | Environmental Violation | 2018 | £45,320 |
| Cwrt Malle Ltd | | | Environmental Violation | 2017 | £44,500 |
| Abingdon Flooring Limited | | | Environmental Violation | 2019 | £43,957 |
| Siteserv Recycling (SW) Ltd | | | Environmental Violation | 2019 | £43,122 |
| Pencefn Feeds Ltd | | | Environmental Violation | 2019 | £40,000 |
| Euticals Ltd | Curia Inc. | pharmaceuticals | Environmental Violation | 2013 | £40,000 |
| Memory Lanes Cakes Ltd | | | Environmental Violation | 2022 | £39,300 |
| Mold Investments Ltd | | | Environmental Violation | 2019 | £38,653 |
| Adgefore Limited | | | Environmental Violation | 2017 | £34,405 |
| Lewis Homes (South Wales) Ltd | | | Environmental Violation | 2020 | £32,116 |
| Par Contractors Limited | | | Environmental Violation | 2021 | £31,987 |
| Asbestos North West & Wales Ltd | | | environmental violation | 2023 | £31,853 |
| Hydropol Project & Management a.s. | | | Environmental Violation | 2017 | £26,860 |
| South Wales Wood Recycling Limited | | | Environmental Violation | 2018 | £25,450 |
| Tower Regeneration Limited | | | Environmental Violation | 2021 | £20,850 |
| Afon Las Hydro Limited | | | Environmental Violation | 2017 | £18,860 |
| Dopower Limited | | | Environmental Violation | 2021 | £17,750 |
| Bob Gay Plant Hire Ltd | | | Environmental Violation | 2022 | £12,687 |
| D J Huxley (Farms) Ltd | | | Environmental Violation | 2018 | £12,670 |
| Gill Waste Recycling Limited | | | Environmental Violation | 2022 | £12,586 |
| DJ & OM Marks & son | | | Environmental Violation | 2020 | £12,327 |
| Langdon Mill Farms Ltd | | | Environmental Violation | 2018 | £11,825 |
| Parc yr Abbot Farm Ltd | | | Environmental Violation | 2017 | £8,125 |
| Digaway Limited | | | environmental violation | 2023 | £7,190 |
| W T Banks & co (Farming) Limited | | | Environmental Violation | 2018 | £7,000 |
| Crofty Point Metals Limited | | | Environmental Violation | 2017 | £7,000 |
| FCM Commercial Services Limited | | | Environmental Violation | 2023 | £6,500 |
| V J Thomas & Sons Partnership | | | Environmental Violation | 2021 | £5,947 |
| Treforris fawr farm (Mr Phillip Davies) | | | Environmental Violation | 2017 | £5,666 |
| Clwyd Spares and Repairs Ltd | | | Environmental Violation | 2019 | £5,300 |
| Siteserv Recycling (SW) Ltd | | | Environmental Violation | 2017 | £5,040 |
| E J Metals Recycling Limited | | | Environmental Violation | 2017 | £4,000 |
| Langdon Mill Farms Ltd | | | Environmental Violation | 2017 | £3,421 |
| Grays Waste Management Limited | | | Environmental Violation | 2020 | £2,875 |
| TE and M Francis and Son Ltd | | | Environmental Violation | 2021 | £2,850 |
| Your Space Projects Limited | | | habitat violation | 2024 | £2,605 |
| Eaden Homes Ltd | | | Environmental Violation | 2020 | £2,250 |
| Knolton Farmhouse Cheese Limited | | | Environmental Violation | 2018 | £1,403 |
| Label Needs LTD | | | Environmental Violation | 2017 | £200 |
| 2 Sisters Food Group Ltd | Boparan Holdings Limited | food products | Environmental Violation | 2017 | £0 |
| Banana Logistics Ltd | | | Environmental Violation | 2017 | £0 |
| Cardiff & Vale University Health Board | | | Environmental Violation | 2017 | £0 |
| Display Recycling Limited | | | Environmental Violation | 2017 | £0 |
| Euro-Worldwide Trading Limited | | | Environmental Violation | 2017 | £0 |
| Hanson Quarry Products (Europe) Limited | HeidelbergCement | building materials | Environmental Violation | 2017 | £0 |
| Mountain Trailers Limited | | | Environmental Violation | 2017 | £0 |
| Mountain View Ranch Ltd | | | Environmental Violation | 2017 | £0 |
| Queensferry Car Breakers Limited, c/o Mechan Accountants | | | Environmental Violation | 2017 | £0 |
| Siteserv Recycling (SW) Limited | | | Environmental Violation | 2017 | £0 |
| SL Recycling Ltd | | | Environmental Violation | 2017 | £0 |
| Solway Foods Ltd | Boparan Holdings Limited | food products | Environmental Violation | 2017 | £0 |
| Sunmagic Juices Ltd | | | Environmental Violation | 2017 | £0 |
| Tarmac Trading Ltd | CRH PLC | building materials | Environmental Violation | 2017 | £0 |
| Ynysmeudwy AFC | | | Environmental Violation | 2017 | £0 |
| Zest Recruitment Staffing Solutions Ltd | | | Environmental Violation | 2017 | £0 |
| Canal River Trust | | | Environmental Violation | 2018 | £0 |
| CB & PSM Davies | | | Environmental Violation | 2018 | £0 |
| City Skips (NW) Limited | | | Environmental Violation | 2018 | £0 |
| Clywd Breakers Limited | | | Environmental Violation | 2018 | £0 |
| Halo Foods Limited | | | Environmental Violation | 2018 | £0 |
| Hydro Schemes UK Limited | | | Environmental Violation | 2018 | £0 |
| Pilkington Asbestos Removal Services Ltd | | | Environmental Violation | 2018 | £0 |
| Queensferry Car Breakers Limited, c/o Mechan Accountants | | | Environmental Violation | 2018 | £0 |
| RR Davies Ltd | | | Environmental Violation | 2018 | £0 |
| South Wales Wood Recycling Limited | | | Environmental Violation | 2018 | £0 |
| Tata Steel UK Ltd | Tata Group | diversified | Environmental Violation | 2018 | £0 |
| TJ's Skip Hire Ltd | | | Environmental Violation | 2018 | £0 |
| City Skips (NW) Limited | | | Environmental Violation | 2019 | £0 |
| ComBigaS Denmark | | | Environmental Violation | 2019 | £0 |
| Dwr Cymru Cyfyngedig | Dwr Cymru Cyfyngedig (Welsh Water) | utilities and power generation | Environmental Violation | 2019 | £0 |
| Dwr Cymru Cyfyngedig | Dwr Cymru Cyfyngedig (Welsh Water) | utilities and power generation | Environmental Violation | 2019 | £0 |
| Gethin Davies & Son | | | Environmental Violation | 2019 | £0 |
| J M & L R Reynolds | | | Environmental Violation | 2019 | £0 |
| Leekes Limited | | | Environmental Violation | 2019 | £0 |
| Maes Elwy Hydro Limited | | | Environmental Violation | 2019 | £0 |
| Mason & Reynolds Holdings Ltd | | | Environmental Violation | 2019 | £0 |
| NAG Recycling Ltd | | | Environmental Violation | 2019 | £0 |
| Rees Metals | | | Environmental Violation | 2019 | £0 |
| Stonewest Construction Limited | | | Environmental Violation | 2019 | £0 |
| World Care (Wales) Limited | | | Environmental Violation | 2019 | £0 |
| Alun Griffiths (Contractors) Limited | | | Environmental Violation | 2020 | £0 |
| Matthew Jeavons MJ Rubbish Removals Ltd | | | Environmental Violation | 2020 | £0 |
| Endurmeta Ltd | | | Environmental Violation | 2018 | £0 |
| Dwr Cymru Cyfyngedig | Dwr Cymru Cyfyngedig (Welsh Water) | utilities and power generation | Environmental Violation | 2018 | £0 |
| DB & RM Edwards & Sons | | | Environmental Violation | 2018 | £0 |
