HCOS4375 - Post detection audit and assessment: rates of duty
The duty rate to be applied for kerosene misused as road fuel is the full heavy oil road rate. For red diesel the rate to be applied is the heavy oil road rate minus the rebated amount paid on the red diesel.
The duty on oil may change following Budget announcements, but has remained stable in recent years.
You will need to make sure that you build these changes into your assessments.
Historic duty rates can be found on the Tax & Duty Bulletins (website) by viewing the latest Hydrocarbon Oils Duties bulletin which has a table of historic duty rates at tab 8 (Website).