"This is a very important step. This decision shows that the government has no tolerance for black money," Central Board of Direct Taxes Chairman Sushil Chandra told PTI.
He said "at this moment", the annoucement made by Prime Minister Narendra Modi in this regard last night will help in curbing the menace to a "large extent".
Sources in the department said the taxman would be keeping an eye on remittances made using the two currency notes, beyond a certain threshold.
The department would work in close coordination with banks and the Financial Intelligence Unit to keep an eye on suspicious transactions resulting after the de-monetisation of the two big currencies, they said.