Price date versus spending date
The estimate base date identifies the purchasing power of the reported total. Escalation moves costs from that base date to expected expenditure dates. Cash flow then shows when the escalated amounts are expected to occur.
General inflation and specific escalation
Labour, steel, electronics, energy or construction may move differently from a broad consumer index. Select indices that reasonably match the cost element and location, and document them.
Currency
State the reporting currency, exchange-rate date and treatment of future exposure. Scenario testing may be more honest than assuming one fixed rate for a long project.
Avoid double counting
Check whether vendor quotes already include future delivery escalation and whether contingency models include price uncertainty. Keep expected escalation distinct from uncertainty around escalation.