ABC enterprise, Inc. secured a 20,500,000 loan from Union bank to be paid after 5 years at 6 percent interest per annum. The loan was partially secured by a mortgaged land and building with a fair value of 19,750,000. In addition, the contract of loan and mortgage was written in a document duly notarized.

how much are the total documentary stamp tax due on the real property mortgage and who is responsible for filling the documentary stamp tax return and payment to the BIR?