When triggered, fixed amount promotions are responsible for adding a fixed amount discount to the orders involved.
Fixed amount promotions are defined by currency code and can be restricted to a specific active market (in which case the currency code is inherited by the market's price list). Within the time window given by their activation and expiration dates, fixed amount promotions that have not reached their total usage limit are considered active. If no promotion rule is associated with an active fixed amount promotion, the related discount is applied to:
All the orders in the specified currency, if the promotion is not restricted to a specific market.
All the orders of the market in scope, if the promotion is attached to a market.
Otherwise, if one or more promotion rules are defined, the promotion is triggered only when it matches all of them.
Multiple fixed amount promotions can be applied to the same order, even concurrently with other promotion types (based on their priority and up to the involved items amount saturation), as long as you don't reach the maximum number of active promotions allowed for your organization.
Discount calculation and distribution
If associated with an SKU list, the total discount due to fixed amount promotions is calculated and distributed on the matching line items of type skus or bundles belonging to that list. Otherwise, on all the taxable items of the order. In both cases, the discount distribution is based on the ratio between the line item amount and the sum of the amounts of all the line items to which the promotion is applied.