Tax Refund Anticipation Check (RAC) fees are often overly costly and hidden by tax preparers, Democratic Senators Elizabeth Warren, Al Franken and Tammy Duckworth warned Tuesday.

RACs are temporary bank accounts established by tax preparers on behalf of taxpayers for direct-deposit tax refunds. The consumers get the money after the tax preparer’s fees are deducted.

They replaced Refund Anticipation Loans after the federal government cracked down on RALs after reports of numerous abuses.

But the senators warned RACs can be fraught with problems as well.

Refund Anticipation Checks can expose taxpayers to unnecessary fees and often lack transparency, they charged.

Often paid preparers do not provide estimates of fees up front or the estimates were less than the actual amounts charged, the senators said, quoting a General Accountability Office report from 2014. RAC fees generally run from $25 to $60 for federal tax returns.

They are asking the GAO to do a study on RACs and other tax-time financial products.

Last year, over 78 million Americans filed taxes electronically through paid preparers and over 53 million used third-party tax software products to prepare and electronically file their own returns, according to the Internal Revenue Service.

On average, Americans spend $120 in tax preparation fees annually.