A computer-implemented method for determining retroactive price adjustments is disclosed. The method can include receiving a first initiation message including a first effective time period and/or a first new price for a part being supplied to a first plant. For the first initiation message, the method can include retrieving information pertinent to an at least one receipt received for the part within the first effective time period. For each receipt, the method can include determining a variance based on the difference between the first or second new price and the receipt price, determining a price adjustment based on the variance and the receipt quantity, and generating a retroactive invoice for enabling transfer of the price adjustment, the retroactive invoice including the variance and the price adjustment. The first effective time period can include an effective start date that is before each receipt date.