Despite the wider shortfall between 2001 and 2006, voluntary compliance remained steady at about 83 percent for both years, the agency said on Friday in its five-year update on the amount of taxes that are never paid.
“On a relative basis, the tax gap is largely in line with the growth in total tax liabilities,” the IRS said in a statement.
“In addition, some growth in the tax gap estimate is attributed to better data and improved estimation methods.”
The gross tax gap, or the amount that was not paid on time, was estimated at $450 billion in 2006, up from $345 billion in 2001.
The net tax gap, or the amount that was never paid, was $385 billion in 2006, compared with $290 billion five years before, the tax agency said.