41 C.F.R. § 105-60.305
Whenever GSA cannot meet the statutory time limit for processing a request because of "unusual circumstances," as defined at 5 U.S.C. 552(a)(6)(A)(iii) , GSA shall, before expiration of the 20-day statutory time period to respond to a request for records, notify the requester in writing of the unusual circumstances involved and of the date by which GSA estimates the processing of the request shall be completed. Where the extension of time is anticipated to exceed 10 business days, GSA shall provide the requester with an opportunity to modify the request or arrange an alternative time period for processing the original or modified request. GSA shall make available its FOIA Public Liaison for this purpose. GSA shall also alert requesters to the availability of the Office of Government Information Services (OGIS) to provide dispute resolution services.
41 C.F.R. §105-60.305