As the Senate prepares to vote this week on a GOP plan to rewrite the U.S. tax code, Republicans are circulating two critical pieces of misinformation about their plan: that everyone in America will get a tax cut and that people will save money on their taxes forever.

At CNN's tax debate Tuesday night, the first question came from Sharon, a single mother of four making about $23,000 a year, who wanted to know if she would get a tax cut under the GOP plan.

Sen. Tim Scott (R-S.C.) gave her a definitive yes, but nonpartisan analysis from Congress' official tax scorekeeper says she only has about a 50-50 chance of being significantly better off.

That's because not everyone gets a tax cut in the Senate Republican plan. It's not possible to tell someone yes or no unless you know their full circumstances.

Sen. Scott held up a piece of paper and said, “I'm happy to share this with you, [it] shows without any question, specifically to your question about your income bracket for your household, the answer is you will pay less in taxes than you did last year. Our proposal cuts your taxes. Anyone that tells you anything other than that is inconsistent with reality.”

Here's the chart his spokesman said he held up. It's from the Joint Committee on Taxation, Congress's official scorekeepers. For the $20,000 to $30,000 income bracket, it shows 46 percent of people get a tax cut of $100 or more in 2019, but 49 percent would pay about the same and 5 percent would pay $100 or more in taxes. In other words, more than half of the people in Sharon's income bracket do not get a significant tax cut. A spokesman for the senator said Sharon would probably fall into the $10,000 to $20,000 bracket, but an even smaller percent of people in that bracket get a tax cut, according to the chart.

The scenario isn't much better when you look at all Americans.

In Missouri, Trump told the crowd that middle class people were going to benefit substantially from this bill.

“Our focus is on helping the folks who work in the mail rooms and the machine shops of America, the plumbers, the carpenters, the cops, the teachers, the truck drivers ... the people that like me best,” Trump said.

But the JCT chart for 2019 shows that just 62 percent would see their taxes cut by more than $100. The rest would pay roughly the same — or more.

Senator Pat Toomey (R-Penn.) went even further Thursday, saying on the Senate floor, “This bill cuts taxes for middle-income families,” even though some would get an increase, according to JCT. Among the middle class — people earning $50,000 to $75,000 — about 10 percent would pay more in taxes in 2019.

Republicans like Toomey frequently talk about how the tax rates are going down for all Americans. But focusing solely on the rates only tells part of the story. Popular tax savings like the state and local tax deduction (SALT) and the personal exemption for you, your partner and your dependents are going away in the Senate GOP plan in its current form. (The bill is subject to changes before its final vote, and one of the changes under consideration would restore part of that SALT deduction). Republicans are lowering tax rates with one hand and taking away some credits and deductions on the other, complicating the math.

Scott, like many of his colleagues, touts the increased Child Tax Credit, which goes from $1,000 to $2,000 per child in the GOP plan. But the mom making $23,000 a year probably doesn't owe any federal income taxes, so a bigger credit helps her little, if at all. The GOP plan gives a token increase to people who actually get money back from the government from a refundable Child Tax Credit.

A late push from Senators Marco Rubio (R-Fla.) and Mike Lee (R-Utah) would make more of Child Tax Credit refundable against payroll taxes, so this mom would be more likely to get a substantial tax cut, but this provision isn't in the bill now. The White House already opposes it, because Rubio and Lee's plan would fund the expanded credit by giving less of a tax cut to corporations.

The second misconception is that the GOP tax cuts last forever. As the bill is written, corporations get a permanent rate cut, but all the tax rate cuts for individuals expire after 2025. That's why every income group making $75,000 or less gets a tax increase (on average) by 2027.

Many Republicans argue that a future Congress won't let the tax cuts for the middle class expire after 2025, and will instead vote to extend them, as they did with the Bush tax cuts for the middle class. But that's not a certainty, and if the extension does happen, the price tag of the bill is actually a lot higher than the $1.5 trillion Republicans claim, a problem for people worried about America's ballooning debt.

Ronna Romney McDaniel, the chair of the Republican National Committee, implied that the tax cuts for families are very large and never go away.

“The tax plan will cut individual tax rates for low- and middle-income Americans, meaning the average middle-class family will see relief of nearly $1,500 per year,” McDaniel wrote in an opinion piece for the Washington Examiner on Wednesday. The White House emailed out her commentary.

The average middle-class family gets a change of about $850, according to the Tax Policy Center, a think tank. That amount also decreases over time. By 2027, more than 65 percent of middle-class families would pay more.

To get around this, GOP lawmakers typically focus just on what happens to the middle class next year. For example, Republicans released a bunch of scenarios showing what happens to various families in 2018, when they are more likely to get a tax cut. They did not say what happens to those same families down the road, when the savings are likely to decline — or go away entirely.

Even setting aside the debate over whether the tax cuts for families will be extended, the middle class still gets hit by another provision in the bill that has not received much attention (except from Greg Ip of the Wall Street Journal, who flagged it early on). That provision is how the bill accounts for the fact that a dollar is worth less and less every year because of inflation.

Every year, more and more middle class families income will be taxed at higher rates because the Senate GOP bill uses a much slower level of inflation (chained CPI) than the measure used in current law (CPI-U). That means that the income level where the 12 percent and the 22 percent tax rates kick in will grow slowly, causing more and more people to bump up into a higher rate.

The same effect also hits a lot of the tax credits in the GOP plan, meaning savings for the middle class like the standard deduction won't be as generous down the road.