Financial Documents for I-20
After you get an admission offer, you need to prove your financial ability to be able to pay the fee and meet living expenses. Only after receiving your financial documents a University can process your I-20. These documents can be sent in the beginning with your application. But in many countires bank charge a significant fee to issue a financial document. In some other countries banks are iefficient and will waste a lot of time in providing you a financial document. Due to these reasons you should consider sending the financial documents only to the University where you actually decide to study.
Again, follow the instructions closely. Photocopies of financial documents are not accepted. There could be a different address for sending the financial documents. If you get a TA or RA the University may not require your financial documents anymore. But you may still be required to submit some paperwork before you get your I-20.