USCIS [U.S. Citizenship and Immigration Services] Fee Waiver Policies and Data (Fiscal Year 2017 Report to Congress) [open pdf - 4MB]
"This report responds to direction from the U.S. Senate for USCIS [U.S. Citizenship and Immigration Services] to provide policies and data on its use of fee waivers. Pursuant to section 286(m) of the Immigration and Nationality Act, 8 U.S.C. § 1356(m), USCIS is authorized to establish fees for services at a level that will ensure recovery of the full costs of providing all adjudication and naturalization services, including services provided without charge to certain immigrants. The regulations at 8 C.F.R. § 103.7(c) provide discretionary regulatory authority for USCIS to waive fees for certain applications, petitions, motions, and requests. The number of fee waiver request receipts increased steadily between FYs 2013 and 2016, with a more substantial increase from FY 2015 to FY 2016. The number of approvals also increased from FY 2013 to FY 2016, while the number of denials increased from FY 2014 to FY 2016, after a decrease from FY 2013 to FY 2014. In addition to the data on the number of fee waiver receipts, approvals, rejections, and the estimated foregone revenue by fiscal year during FYs 2013-2017,1 the report also provides USCIS's policy guidance relating to fee waivers.2 Each fee waiver request is considered on its own merits, and USCIS may grant a fee waiver when it has determined that the individual is unable to pay the fee on the basis of the individual's overall financial situation. In general, USCIS policy is to consider fee waiver requests when:  The individual is receiving a means-tested benefit;  The household income level (at or below 150 percent of the Federal Poverty Guidelines) renders the individual unable to pay; or  Financial hardship otherwise renders the individual unable to pay."
U.S. Department of Homeland Security: https://www.dhs.gov/