The impact of implementing the intervention on the health budget and on other constraints should be identified clearly and separately.

Importance for decision-making
It is important to determine the net total costs involved in the deployment of a health intervention on a particular scale (see Section 2.8), as these are also a measure of the value of what must be foregone.

The costs of an intervention (even when capital investment is not required) are unlikely to be evenly spread over time, but often have large initial costs offset by later health benefits and at times, cost savings. Decision-makers responsible for annual budgets must assess the timing of the impact as well as the magnitude of the expected incremental costs when deciding if the benefits of an intervention exceed the health opportunity costs. This becomes especially important when later health benefits or cost savings are uncertain, since implementation will require the commitment of resources that may be unrecoverable should subsequent evidence suggests the intervention is not worthwhile (or not cost effective) and should be withdrawn (see Part 2.9).

In addition to expenditure constraints decision-makers may be subject to other infrastructural or resource limitations, such as lack of laboratory capacity or workforce limitations. Decision-makers (at national, regional, or local level) must be able to assess the impact of an intervention in each of these domains to properly determine whether the benefits exceed the health opportunity costs. This may also facilitate some consideration of which constraints have the greatest impact, and the potential value of policies that modified these, such as removing restrictions on the use of donated resources or increasing investment in training health workers.

Since non-health benefits and costs do not impact health budgets or other constraints on health care, they should be assessed separately (see Part 2.7).

Method specification
Budget impact should be presented in a manner that is relevant to the decision problem and the needs of the intended decision-maker. The budget impact should be disaggregated and reflect the costs to all parties as a result of implementation of the intervention (cost outputs). This includes (but is not limited to) impact on government and social insurance budgets, households and direct out of pocket expenses, third-party payers, and external donors. Budget impact should be projected annually for a period appropriate to the decision problem.