"For the IRS to appropriately enforce the tax laws against high earners and large corporations, it needs funding to hire and train revenue agents who can decipher their thousands of pages of sophisticated tax filings," said the report. "It also needs access to information about opaque income streams—like proprietorship and partnership income—that accrue disproportionately to high-earners."  

The report also called out tax preparers whose help goes from avoidance to evasion. It said that these preparers are well aware of the IRS's resource issues, and that the consequences of their clients' underpayments are viewed as minor, and so voluntary compliance rates tend to be lower. 

This is why Treasury has proposed significantly increasing the IRS budget, specifically $80 billion of investment over the coming 10 years in enforcement, information technology and taxpayer services, which it believes will generate an estimated $320 billion in additional tax collections during that 10-year period. It also wants to implement a more robust system of third-party reporting, turning especially to banks to provide the IRS with information that the taxpayers may not offer, 

"There is a direct relationship between the information the IRS has at its disposal to verify that a taxpayer has properly paid her tax liabilities, and her voluntary compliance rate,"  said the Treasury report. "For ordinary wage and salary income, compliance with income tax liabilities is nearly perfect (1 percent noncompliance rate). In stark contrast, for opaque income sources that accrue disproportionately to higher earners—like partnership income, proprietorship income, and rental income—noncompliance can reach 55 percent."

In particular, the report said that half of the individual income tax gap accrues to income streams from proprietorships, partnerships and S-corporations, where there is either little or no information available to the IRS to verify the veracity of tax filings.

If this plan sounds familiar, that is because it is basically the same proposal that had originally been in the infrastructure plan before Republican opposition killed the provision.