Republican Presidential candidate Ted Cruz’s plan to impose a flat 10 percent tax on all personal income and greatly lower the corporate tax rate would cost the federal government at least $8.6 trillion over a decade, according to a new analysis.

The plan would be the second most expensive tax proposal in the GOP presidential field, with only businessman Donald Trump offering a proposal that would add more in government debt over the next 10 years, according to data released Tuesday by the nonpartisan Urban Brookings Tax Policy Center. 

[A $9.5 trillion price tag for Trump’s tax plan]

Republican presidential candidates have been quick to campaign on promises to cut taxes, but because most have yet to detail how they would slash spending to offset this lost revenue, analysts have projected their proposals would be deficit busters.

Cruz’s plan also falls short of fulfilling the Texas senator’s promise that his flat tax system would be so simple that taxpayers would file their returns on a postcard.

Cruz would eliminate nearly every tax deduction except those for charitable contributions and mortgage interest and would increase the standard deduction to make doing your taxes easier. He would also eliminate all credits except the earned income tax credit for low income workers and the child tax credit.

The streamlined system is the simplest plan released by any presidential candidate, but analysts said Cruz’ proposals would still require most people to fill out more than a postcard.

“I would think the form would have to look not that different than what you do now,” said Tax Policy Center Co-Director Eric Toder.

The Cruz campaign declined to respond to questions Tax Policy Center staff sent about the plan, which meant it had to make some assumptions about Cruz’s proposal in areas where there was a lack of detail.

The proposal also falls short of Cruz’s promise that under his plan every income-level would see double-digit increases in after-tax income.

Analysts found that while most workers would receive a tax cut, the lowest income workers would see their after-tax income decline by 0.6 percent.

There would be a 16 percent flat business tax under Cruz’s proposal, which functions like an across-the-board consumption tax that would increase the amount workers are taxed by their employers. Those low-income workers who don’t make enough to file taxes wouldn’t benefit from the expanded standard deduction that is meant to offset the payroll-side increases.

“Somebody below the standard deduction amount, they cannot benefit much,” said Tax Policy Center Director Leonard Burman, who served in the Treasury Department during the Clinton administration. “They would benefit very little from repealing the corporate income tax so on net they would end up paying higher taxes under the Cruz plan.”

Cruz’s business tax has also been criticized by fellow presidential candidate Sen. Marco Rubio (R-Fla.), who compared it to a European-style value added tax. Burman said Rubio is correct and Cruz’s system would impose a version of the consumption tax system popular in much of Western Europe. The center estimates Rubio’s tax proposal would cost the government at least $6.8 billion in lost revenue over the next decade.

[The VAT tax fight between Rubio and Cruz]

The biggest beneficiaries under Cruz’s plan would be the top 0.1 percent of earners. People earning over $3.7 million per year would see an average tax break of more than $2 million in the first year, according to the analysis.

The plan would add $10.2 trillion to the national debt in the first decade, according to the center, when you include interest payments on the additional government borrowing that would occur.

Cruz isn’t alone in crafting a tax plan that would cost the federal government trillions while delivering big benefits for the wealthy, all of the Republicans running for president are doing it.

“All of the plans benefit high income people more than low income people,” Burman said. “They are enormous tax cuts compared to the current system and they are enormously regressive.”

Analysts said the lost revenues could be reduced through spending cuts, including Cruz’s plan to repeal the Affordable Care Act, but Cruz and most other Republican candidates have yet to provide detailed lists of the cuts that should be made.

Burman said the plan would make it easier and more beneficial for businesses and individuals to invest. Lower tax rates and benefits for businesses would likely encourage major investments in the early years of the plan, but analysts said they expect interest rates would increase and the economy would decline as a result of the ballooning debt.

“The plan by itself, not including the unspecified spending cuts, would surely depress the economy,” Burman said.