Government's move to increase income tax collection by making income tax return submission mandatory for every Taxpayers Identification Number (TIN) holder might not have that significant an impact on revenue collection for the national exchequer.   "There is an inbuilt system in the law that TIN holders will submit their returns, this new proposed system will remain a call, it does not seem that a good number of TIN holders will be responding," former National Board of Revenue (NBR) chairman Muhammad Abdul Mazid told UNB.   A senior NBR official also said that due to understaffing the revenue collection agency may anyway fail to get the whole fruits of this proposed law.   Finance Minister AHM Mustafa Kamal while placing the budget proposal for the 2020-21 fiscal proposed to amend the Income Tax Ordinance to make submission of tax return mandatory for all TIN holders.   "When comes into force, this provision will potentially seal the scope of tax evasion, and significantly increase the number of return filers," he said in his budget speech in Parliament on Thursday last.