We seek feedback and advice about how we estimate the gap from external and internal subject matter experts. Based on this advice, the reliability rating for this estimate is high (with a score of 21).
The main data source is an external survey of large-scale petroleum and diesel producers. Small producers are not covered through this survey, but their market share is negligible given the small number of participants in the fuel industry.
Our activities confirm high levels of compliance overall. However, assumptions around the volumetric calculations may have an impact. Although there are some reservations about the data, the methodology employed is robust.
Figure 3: Reliability rating scale from very low to very high – fuel excise tax gap
How we estimate and reduce the fuel excise tax gap for 2020–21.