WASHINGTON (Reuters) - Missing from President Donald Trump’s budget proposal this week was an annual report, known as the Green Book, that presidents have issued for many years to spell out their tax goals in detail, an omission that tax experts called telling.

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The Green Book, named for the color of its cover in recent years, is not that big a deal as a document, but its absence this year shows that the Trump White House lacks a clear vision for what to do about overhauling the tax code, experts said.

“I think it’s as simple as no tax plan equals no Green Book,” said Donald Marron, director of economic policy initiatives at the Urban Institute, a liberal think tank.

Democratic lawmakers on Thursday in two Senate hearings criticized the president’s fiscal 2018 budget proposal, released on Tuesday, and some of its core tax components.

Democratic Senator Chris Van Hollen called the budget proposal and its tax assumptions “fantasy flim-flam.”

Treasury Secretary Steven Mnuchin, appearing at one of the hearings, said the budget proposal did not consider how new tax laws would impact government revenues and the deficit because the Trump administration did not have a detailed tax proposal.

“When the president’s budget was done, we were not ready to have a full-blown tax reform plan,” Mnuchin said, adding that tax details would be worked out with Congress, then made public.

A Treasury Department official said separately it would not help to publish details while talks with Congress were underway.

“Releasing a Green Book of tax policy proposals as we work towards comprehensive tax reform would contradict that effort,” the Treasury official said in an email.

The last Green Book was issued by the Obama administration in February 2016 and ran 283 pages. Past Green Books going back to 1990 are available on the Treasury Department website.

As a candidate, Trump, in his 125th day in power, promised voters that he would work with Congress and seek passage in his first 100 days of “massive tax reduction and simplification.” He has not yet offered any tax legislation.

On April 26, the administration released a one-page list of tax proposals summarized in 12 bullet points. Tuesday’s budget repeated the one-page summary, including a proposal to end the estate tax on inheritances paid by a few wealthy Americans.

Despite this policy position, the Trump budget included a projection of $328 billion in estate tax revenues for 2018-2027.

“I’ve seen lots of tricky budgets before, but this may take the cake,” said Democratic Senator Mark Warner. “You assume abolishment of the so-called death tax, estate tax, but ... you still count the revenues from the estate and gift tax, which is kind of a tricky thing. I would call that double-counting.”