This excerpt taken from the GPS 10-Q filed Jun 9, 2009.
27.3 Billing Adjustments
Supplier shall provide Gaps Infrastructure Partnership Executive with a monthly summary of credit and debit billing adjustments. The summary shall include, but not be limited to, the number and types of billing adjustments identified, the number of billing adjustments resolved, and the number and types of billing adjustments that are outstanding. Supplier shall insure that all billing debits and credits, including associated taxes, are distributed on the billing reports and the invoice and are shown at the proper hierarchy level. If a billing adjustment is found to exceed *, then Supplier shall notify Gaps Infrastructure Partnership Executive before processing the billing adjustment to the billing report and the invoice. Supplier shall process all billing adjustments on the reports and invoice. In no event shall a billing adjustment result in a net increase to any Charge invoiced more than * days after the original invoice date for that Charge.