I feel lots of people source of income is not verified and they do in small amount take undue advantage of the tax system.As there is no proper tacking of the source of income and verification.
Example.
A buys a house .His mortgage is around 2500$ (PITI). He does file his tax return with income below 1000 $.But he still own his his house.Hows that possible.In doing so he pay less tax but get max benefits.
In doing so, the gov. to can run his background check.This helps to collect more tax from individual as well as track his activities for security issues.



