The US Department of the Treasury, in its document 'General Explanations of the Administration’s Fiscal Year 2025 Revenue Proposals,'  said currently the law does not provide tax rules specifically addressing digital assets, with the exception of certain rules relating to broker reporting and reporting of cash transactions.

It explained that the "computational effort" involved in digital asset mining can be "substantial" and can therefore require a "correspondingly large amount of energy".

The Department said: "The increase in energy consumption attributable to the growth of digital asset mining has negative environmental effects and can have environmental justice implications as well as increase energy prices for those that share an electricity grid with digital asset miners. Digital asset mining also creates uncertainty and risks to local utilities and communities, as mining activity is highly variable and highly mobile. "

Under the proposal, "any firm using computing resources, whether owned by the firm or leased from others, to mine digital assets would be subject to an excise tax equal to 30 percent of the costs of electricity used in digital asset mining."

The Department has included a proposal that "any firm using computing resources, whether owned by the firm or leased from others, to mine digital assets would be subject to an excise tax equal to 30% of the costs of electricity used in digital asset mining." 

The Greenbook says firms engaged in digital asset mining would be "required to report the amount and type of electricity used as well as the value of that electricity, if purchased externally." Firms that "lease computational capacity" would be "required to report the value of the electricity used by the lessor firm attributable to the leased capacity, which would serve as the tax base". Firms that "produce or acquire power off-grid, for example by using the output of a particular electricity generating plant, would be subject to an excise tax equal to 30% of estimated electricity costs." 

The proposal would be effective for taxable years beginning after December 31, 2023. The excise tax would be phased in over three years at a rate of 10% in the first year, 20% in the second, and 30% thereafter. 

The nine reports together "articulate a clear framework for responsible digital asset development and pave the way for further action at home and abroad". They call on agencies to promote "innovation by kickstarting private-sector research and development and helping cutting-edge U.S. firms find footholds in global markets".

But the reports also call for measures to mitigate the downside risks, such as increased enforcement of existing laws and the creation of "common-sense efficiency standards for cryptocurrency mining". 

Recognising the potential benefits and risks of a U.S. Central Bank Digital Currency (CBDC), the reports encourage the Federal Reserve to "continue its ongoing CBDC research, experimentation, and evaluation and call for the creation of a Treasury-led interagency working group to support the Federal Reserve’s efforts".