According to 2012 Congressional Research Services (CRS) report on U.S. Foreign Aid to the Palestinians, the aid is intended for “preventing terrorism” and “meeting humanitarian needs and preventing further destabilization, particularly in the Gaza Strip.” Where these two priorities intersect is subject to a host of vetting and oversight requirements and legislative restrictions.   The report calls on Congress to evaluate and assess future aid programs and their “oversight, vetting, monitoring, and evaluation requirements.”

On page 12 of the report, there is a section titled, Vetting Requirements and Procedures.  It says, in part:
“USAID subjects its programs worldwide to vetting requirements to ensure the proper use of funds appropriated through its accounts…This vetting process has become more rigorous in recent years in response to allegations that U.S. economic assistance was indirectly supporting Palestinian terrorist groups, and following an internal audit in which USAID concluded it could not “reasonably ensure” that its money would not wind up in terrorist hands.”
It continues, quoting a USAID statement from 2009:
“All NGOs applying for grants from USAID are required to certify, before award of the grant will be made, that they do not provide material support to terrorists…. Before making an award of either a contract or a grant to a local NGO, the USAID West Bank/Gaza Mission checks the organization and its principal officers, directors and other key personnel against lists maintained by the Office of Foreign Assets Control (OFAC) within the U.S. Department of Treasury. The Mission also checks these organizations and individuals through law enforcement and intelligence community systems accessed by USAID’s Office of Security. At present, the Mission collects additional information up front in addition to the individual’s full [four-part] name, such as a government issued photo-ID number and the individual’s date and place of birth…. [USAID’s] West Bank/Gaza program possess[es] the most comprehensive partner vetting system for foreign assistance throughout the U.S. Government.”
The Partner Vetting System (PVS) has been widely criticized by humanitarian and peacebuilding NGOs in the U.S. who strongly oppose its implementation. Click here to learn more about PVS. 
The CRS report says that between 2009 to mid 2012, annual U.S. assistance to the West Bank and Gaza Strip has averaged nearly $600 million. Of that, approximately $300 million on average per year is dedicated to project assistance for the West Bank and Gaza through U.S. government grants to NGOs.