GR/IR is the SAP process designed to perform the three-way match – purchase order, material receipt, and vendor invoice. It uses a clearing account to record the offset of the goods receipt and invoice receipt postings. Once fully processed the postings in the clearing account will balance.
This balancing is performed at the Purchase Order Line Item based on the quantity entered on these documents. Price variance is calculated and recorded with these posting; exchange rate variance can be as well. Small differences can be written off using transactions MR11.