President Obama’s executive amnesty will cost taxpayers about $1.7 billion in tax credits to illegal immigrants over ten years, according to a new report.

If the courts allow Obama’s executive amnesty to proceed, millions of Illegal immigrants would be able to obtain Social Security Numbers and work permits.

The Internal Revenue Service has repeatedly acknowledged that such amnesty beneficiaries would be able to file up to three years in back taxes and claim refunds such as the Earned Income Tax Credit.

An estimate calculated by the congressional Joint Committee on Taxation, at Sen. Chuck Grassley (R-IA) and Sen. Orrin Hatch’s (R-UT) request and obtained by McClatchy, says that over the next ten years EITC refunds provided under Obama’s executive amnesty could total $1.7 billion. McClatchy notes almost all the payment would be made in the first five years.

Earlier this week the IRS again defended the policy, which would allow amnesty beneficiaries to claim taxpayer money for illegal work.

“[We] have reviewed the relevant statutes and legislative history, and we believe that the 2000 [Chief Counsel advice] is correct,” IRS Commissioner John Koskinen wrote in a letter to Grassley. “The CCA concludes that a taxpayer may claim the earned income tax credit (EITC) for a taxable year using a social security number (SSN) acquired in a later taxable year.”

Following the IRS’ defense, Grassley announced that he is working on legislation that would keep the tax code from rewarding those who broke immigration laws.

“With the stroke of a pen, the President rewarded those working illegally in the United States with a tax benefit that is designed to encourage low-income individuals to enter the workforce,” Grassley said. “Given that the IRS is intent on standing by its present interpretation of the eligibility requirements, I’m working on legislation to uphold an important principle that many of us in Congress support.”

A recent Congressional Research Service report found that in the first year of amnesty, an amnesty beneficiary could potentially claim more than $35,000 in EITC and Child Tax Credits in their first year of amnesty.