Project 5.1 The averted loss component of an offset is the protection of biodiversity that would, if it were not for the offset, be lost at some definable point in the future. Calculating the amount of averted loss achieved under an offset proposal therefore requires an evaluation of the likely outcome at the offset site both without the offset (‘business as usual’ scenario) and with the offset (for e.g., protection). Averted loss is included in the calculations of two components within the Guide: averted loss of condition using the ‘quality’ score and averted loss of area using the Risk of Loss (ROL) score. This report deals only with estimating the ROL score, which describes the likelihood that the proposed offset site will be lost completely due to anthropogenic impacts such as clearing. The Guide requires ROL estimates to be included when assessing a direct offset proposal. If an offset proposal estimates a high ROL in the ‘without offset’ scenario, averting loss of area (an ‘averted loss offset’) will make a greater contribution to the total offset requirement than if a low ROL is estimated, thereby reducing the remaining offset benefits required. If the ROL is overestimated, it is likely that the full anticipated conservation gains will not occur, and impacts on the threatened species or ecological community will not be adequately compensated. This risks falling short of the Offsets Policy’s principle of ‘improving or maintaining the viability’ of the target threatened species or ecological community. It is therefore crucial that evidence based, robust ROL estimates are derived and used in assessing offset proposals, to ensure that offsets effectively deliver an overall conservation outcome that improves or maintains the viability of the protected matter.