US short term visa holders (non-US citizens) need to pay $20 as a reference fee in addition to other fees. All non-US citizens residing in the U.S. for less than 2 years need to pay $20 as a reference fee in addition to other fees. US green card holders and the applicants who have a US long term visa (3 years or more) do not have to pay the reference fee. Reference fee is to facilitate a routine background check and/or other application processing.