You may think from the above statement is only of passing interest but actually operating illegally could be as simple as not being compliant with the conditions which apply to a waste exemption or not following through the requirements when working under the CL:AIRE DoW CoP. Non-compliance could therefore be taken as working illegally without a permit.
Following a consultation paper earlier this year which indicated strong support from industry the government confirmed its intention to legislate to extend the scope of Landfill Tax to illegal waste sites from 1 April 2018 ie all disposal sites without a permit. In September the government published the draft legislation and associated explanatory information. To read more please go to https://www.gov.uk/government/publications/landfill-tax-disposals-not-made-at-landfill-sites.