1. The amount recognized as a provision should be the best estimate of the expenditure required to settle the present obligation at the end of reporting period
2. Where a single obligation is being measured, the individual most likely outcome adjusted for the effect of other possible outcomes may be the best estimate
3. Where there is a continuous range of possible outcomes and each point in that range is as likely as any other, the midpoint of the range is used
4. Where the provision being measured involves a large population of items, the obligation is estimated by "weighting all possible outcomes by their associated possibilities" (expected value)