The federal Freedom of Information Act generally requires agencies to “determine” within 20 working days after the receipt of a FOIA request whether it will comply with the request and notify the requester accordingly.1 In practice, however, this deadline is largely aspirational as many federal agencies have considerable FOIA request backlogs and therefore often fail to meet this statutory deadline.
You should be prepared for the unfortunate likelihood that your request will take longer than 20 working days to be fulfilled. Notwithstanding, the FOIA allows you to administratively appeal excessive, undue delays. Such appeals may, although not always, have the effect of speeding up your request (especially if you are truly intent on filing a lawsuit because of the delay and let the agency know as much).
Given the reality of processing delays, federal FOIA requests are not always a reliable means of newsgathering for short-term, deadline-based reporting. You should ideally conceive of how access to federal government information will aid your reporting at the outset of an assignment and file your FOIA requests as soon as possible, including a well-reasoned plea for expedited review in such requests.
1 See 5 U.S.C. § 552(a)(6)(A)(i).