The Environment Agency, Natural Resources Wales, the Scottish Environment Protection Agency and the Northern Ireland Environment Agency have jointly published Technical Guidance WM3 Waste Classification — Guidance on the Classification and Assessment of Waste, available from www.gov.uk as a PDF download.
The webpage on which this was published notes that the WM2 guidance applied until 30 June 2015, after which the “new” WM3 replaces it.
The change from WM2 to WM3 was brought into force by the Hazardous Waste (Miscellaneous Amendments) Regulations 2015 (SI 2015 No. 1360). These give effect to the changes required by Commission Regulation 1357/2014 (and Commission Decision 2014/955/EU). There will be different implementing legislation in Wales, Scotland and Northern Ireland.