A unit of risk accounting is essentially the basis upon which risk is measured and reported across an organization. Its primary characteristics include:

• Risk metric: The specific measure used (e.g., Value at Risk, Expected Shortfall).
• Confidence level: The statistical probability used in the measurement (e.g., 95%, 99%).
• Time horizon: The period over which the risk is assessed (e.g., 1 day, 1 year).

Complex simulation is a methodology or technique (such as Monte Carlo simulation) used to compute or aggregate the risk metric, rather than a defining characteristic or parameter of the unit of risk accounting itself.