President Trump's fiscal 2019 budget proposal calls for a $15 billion spending increase for the Internal Revenue Service to help it enforce tax law and bring in tax collections, a measure meant to help ensure that the sweeping tax overhaul Trump signed into law in December is successful.

"By investing in the modernization of Internal Revenue Service (IRS) systems, the budget would help make the implementation of tax reform successful and support the president’s vision of making tax filing simpler for hardworking Americans," reads the budget, released Monday morning.

The budget doesn't propose an increase in base funding for the IRS. The agency would get $11.1 billion, down from $12 billion.

But Trump and budget director Mick Mulvaney propose infusing the agency with nearly $15 billion to enforce tax collections, starting with $320 million in 2019 and then growing from there.

The additional spending is expected to bring in more money from the federal government, on the assumption that paying more for tax collection will bring in more unpaid taxes. Altogether, it would bring in $44 billion over the next decade. The net savings would be $29 billion.

Former IRS Commissioner John Koskinen testified last year that each additional dollar of spending on enforcement more than pays for itself.

Congressional Republicans have grown receptive to the idea of additional funding for the IRS to carry out the tax law, after years of cutting the agency's spending and forcing it to shed employees.

The tax law is the party's signature achievement and includes several provisions that will prove challenging to implement, including a special new tax break for non-corporate businesses and a complete overhaul of the system of taxing international profits.