Plain definition
Trailing twelve months, or TTM, is a measure for the most recent twelve consecutive months ending on a stated date. It reduces the distortion of one month or one season, but it can lag a rapid business change.
Illustrative example
Monetary examples use Saudi riyals (SAR). The same principles apply in other currencies.
At 30 June, a retailer uses July-to-June TTM revenue of rather than June sales alone. July-to-December includes its normal peak, so the measure is more comparable with prior twelve-month periods. A sharp June margin fall is still shown separately because the TTM total would dilute the warning.
Why it matters
TTM helps compare a seasonal business on a full-cycle basis, which prevents a single peak month from driving capacity or valuation conclusions. Current indicators are still needed for a turning point.
Practical consequence
Name the end date and the twelve included months, keep definitions consistent, and pair TTM with current-month and forecast measures. Do not treat it as a cash forecast or proof that recent performance will persist.