Dr. Patrick Moran:

Tagging is really a way of mapping out where the money is going. Increasingly, many of the policy challenges the Government is trying to deal with are not confined to one Department. They are cross-cutting, whole-of-Government problems. The idea behind tagging is that one can track and monitor the flow of resources against those policy goals and societal challenges, so one can have more confidence that our resources are being employed in the best way possible, in line with Government priorities. On a practical level, it means tagging each of the subheads, which they are called in the Revised Estimates Volume, REV, which is the lowest level of detail one can get about where money has been allocated across Departments using these tags. It allows one to look at the totality of public expenditure through a different kind of lens, so one will be able to say that a certain percentage went to the mental and physical health dimension of well-being and a certain percentage went to safety and security.

One would be able to cross-reference those too because much of the spending is on multiple goals, or is not just confined to one. The insights which that gives are supposed to quantify how much expenditure is going towards a particular goal and that can then be used in combination with metrics and performance to look at the issue of value for money and also to make sure the priorities of Government are reflected in the budget.