The Internal Revenue Service (IRS) should – but won’t – clarify how taxes are levied on cryptocurrencies and cryptocurrency transactions in the U.S., the government’s top auditing institution said Wednesday.

The Government Accountability Office (GAO), a U.S. Congress watchdog, published a report in response to a request from Rep. Kevin Brady (R-Texas), evaluating the IRS’s existing approach and public guidance surrounding cryptocurrencies.

The office had three recommendations for the U.S. tax collector, as well as an additional related recommendation for the Financial Crimes Enforcement Network (FinCEN), a bureau of the U.S. Treasury Department. Notably, one of its recommendations was to clarify that some of the IRS’s recent guidance is not binding or authoritative – and the agency rejected this recommendation.

“Part of the 2019 guidance is not authoritative because it was not published in the Internal Revenue Bulletin (IRB). IRS has stated that only guidance published in the IRB is IRS’s authoritative interpretation of the law. IRS did not make clear to taxpayers that this part of the guidance is not authoritative and is subject to change,” the report said.

Wednesday’s GAO report was reported earlier by Bloomberg Tax.

The IRS’s 2019 guidance answered some questions around the tax treatment of cryptocurrencies but “prompted new concerns among virtual currency stakeholders,” the report said. Complying with tax requirements may be difficult, and the GAO report suspects that trading activity may be underreported due to a lack of clarity around what should be reported.

A further complication comes from foreign account reporting requirements, the GAO said. Specifically, it is unclear whether foreign bank account reporting requirements under the Bank Secrecy Act (BSA) and Foreign Account Tax Compliance Act (FATCA) reports apply to cryptocurrencies.

Indeed, even the wording around cryptocurrencies is vague. The IRS and other elements of the federal government have been referring to cryptocurrencies as virtual currencies, but as noted by Coin Center’s Jerry Brito, the term can also refer to digital monies used in video games (UPDATE: The IRS modified this language to exclude video game currencies late Wednesday).

The term “convertible virtual currency” may more specifically refer to cryptocurrencies, and has appeared in White House publications and IRS documentation (though not its 2019 FAQ).

The GAO recommended the IRS add a note saying its 2019 FAQs are not binding guidance, clarify third-party reporting requirements and clarify the reporting requirements around FATCA. The GAO also recommended FinCEN, in coordination with the IRS, share more information about applying foreign account reporting requirements under the BSA.

The IRS agreed with the second recommendation but disagreed with the first and third, the GAO report said. FinCEN also agreed to share more information.

“We continue to believe that including such a statement would provide more transparency and help taxpayers understand the nature of the information provided in the FAQs,” the GAO said.