You will receive an acknowledgement letter from USCIS within 20 business days from the receiving date of your Form G-639, Freedom of Information Act/Privacy Act Request. This letter will contain the processing time involved in your specific case. However, if there are any omissions in the submitted Form G-639, USCIS will issue a request for additional information and thus the response time may be extended for another 10 business days.
The processing time of a FOIA request itself varies significantly, from 4 weeks to 6 months. USCIS uses a first-in/first-out, the 3-track processing system which influences requests processing time. The request will receive Track 1 or Track 2 status depending on the complexity of your FOIA request. Thus, processing of a request for entire immigration file is considered Track 2 and it will take much longer than a simple request for a specific simple document. That is why it is recommendable to limit FOIA request to specific information/documents that you need. As for Track 3, it is assigned only to cases involving persons who are to appear before an immigration judge.
Meanwhile, in some cases you may be eligible to apply for expedited processing or priority processing of your G-639, FOIA request. Please see our articles for more details as to the matter.