All federal agencies are required to respond to a FOIA request within 20 business days, excluding Saturdays, Sundays, and legal holidays.  This period does not begin until the request is actually received by the FOIA office of the component that maintains the records sought.  An agency is not required to send out the releasable documents by the last business day; it can send you a letter informing you of its decision and then send out the documents within a reasonable time afterward.