The illicit market in diesel has continued a decade-long decline in size, and is so small in Great Britain it is difficult to quantify, but it still accounts for 8% of the Northern Irish market with a loss to the Exchequer of £50m.
These are the findings of the latest Tax Gaps report by HM Revenue & Customs (HMRC), which estimates the difference between the amount of tax that should, in theory, be collected by HMRC, against what is actually collected.
The report covers the tax year for 2014-2015, and admits is difficult to estimate the size of the illicit GB diesel market because it is so small, stating its best estimate is less than 1% of the market and less than £50m in lost tax.
It adds that the reduction in the illicit market share of Great Britain (GB) diesel continues a long-term trend from 5% in 2005-06.
The report estimates the value of the Northern Ireland diesel tax gap at £50m and says it has been declining in the long term from 19% in 2005-06 to 8% in 2014-15.
HMRC also estimates the market share for fraudulent petrol in Northern Ireland, and the rest of GB to be negligible in 2014-15.