Two weeks after introducing their bill to overhaul the Affordable Care Act to heated criticism, House Republicans unveiled amendments to the plan. Here's what you need to know about the legislation and its changes. (Bastien Inzaurralde,Sarah Parnass,Jenny Starrs/The Washington Post)

When House Republicans unveiled on Monday a plan to replace the Affordable Care Act, one thing was immediately clear: the new approach could create a major shift in taxes for low-and-middle income people while delivering a $600 billion tax break, primarily to the rich.

Republicans have long criticized the ACA for creating a whole new system of tax credits based on individual income levels intended to help people buy health insurance on established health-care exchanges. The new plan replaces those credits with a fresh series of tax subsidies based on age and income that are intended to make it easier to buy insurance on the private market.

The GOP proposal would also eliminate the complex web of tax increases established by Obamacare on people and companies — everything from  tanning salons to medical device manufacturers — that help pay for benefits in the current law, like free breast cancer screenings, preventative care, and allowing people to remain on their parents’ insurance until the age of 26. They’d also help underwrite the cost of prohibiting insurers from banning those with pre-existing conditions.

The combination of maintaining the most popular and well-known portions of Obamacare — and cutting taxes — is expected to cost the federal government as much as $600 billion over ten years, according to the non-partisan Joint Committee on Taxation.

But, Republicans say, their plan is a silver bullet aimed at remedying years of unfair tax increases and uneven health coverage for people across the income brackets. House Speaker Paul D. Ryan (R-Wisc.) called the GOP plan a chance to “equalize the tax treatment of health care for all Americans.”

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So far, Republicans have not released critical details to back up those promises. They have not revealed any detailed accounting on how different income and age groups will be affected by the GOP plan and how much the plan will cost the government. That information is typically revealed along with any major legislation. But GOP leaders have not yet said when they will make it public.

Here’s what we do know: The GOP plan would provide major tax breaks for the wealthiest one percent of the population. Low-income people are most likely to see their credits slashed while middle-income earners could have access to bigger, better credits down the line.

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Taxpayers should also prepare for more tax changes in the future as Republicans plan to stall a tax on high-value employer coverage known as “Cadillac plans.” That planned 40 percent tax on pricey health-care plans may be necessary to offset the cost of those popular benefits that Republicans have vowed to protect.

There are also still many unanswered questions about whether the GOP approach can avoid creating a huge budget deficit over the long haul. Democrats and some conservatives don’t necessarily believe the math will add up.

Here are five ways the GOP proposal would change the tax system:

1. This is a major tax cut for the rich. House Republicans plan to eliminate nearly every tax increase that was included included in the ACA, many of which were levied on high-income earners. Democrats insist that some tax increases were necessary to offset the cost of expanding coverage and overhauling the health-care system to ensure people received a minimum level of coverage.

Republicans say they’ve found a way to pay for wider coverage that doesn’t include taxes on the on the rich, which are the backbone of the current system. The new GOP plan would repeal two of the biggest-ticket taxes in the ACA: a 3.8 percent tax on investment income; and a 0.9 percent levy on income over $200,000 for individuals and $250, 000 for married couples filing jointly. Those two taxes hit fewer than four million households making up the top 2.5 percent of taxpayers, according to IRS data.

“Those taxes raise over $300 billion over a decade,” said Scott Greenberg, an analyst at the conservative-leaning Tax Foundation “The impacts of those taxes are largely on high-income households.”

Wealthy earners would also benefit from a rule to halve the penalty on using money from a Health Savings Accounts on expenses not related to health care. Current limits allow individuals to directly transfer up to $3,400, and families up to $6,750, into an HSA without paying any taxes on the income.

“They’re very attractive to highly compensated individuals who have already maxed out other tax-preferred retirement plans,” said Gordon Mermin, a senior research associate at the Tax Policy Center. “They can use it in retirement as a retirement account. If it turns out they have health expenses and use it for that, then they’re not paying tax at all.”

Wealthy people already make up the majority of people using the accounts. Families earning over $60,000 made up nearly 65 percent of the total that contributed in 2014, according to recent data from the Treasury Department.  Nearly two-thirds of those people earned between $75,000 and $200,000.

2. Lower-income workers are going to feel the biggest squeeze. The poorest workers would see a nearly opposite scenario under the GOP plan. Most estimates say they would be the hardest hit.

Low-income people traditionally do not participate in the Health Savings Account program and often rely more heavily on the existing tax subsidies.

The folks who lose the most under this proposal are the low income people who qualify for a relatively large tax credit today,” Mermin said. “It will either mean they will be paying a lot more for their plans or buying a plan that covers a lot less. They could wind up with a much higher deductible.”

The GOP plan calls for tax credits ranging from $2,000 per year for those under 30 to $4,000 per year for those over 60. The full credit would be available for individuals earning up to $75,000 a year and up to $150,000 for married couples filing jointly. The credits would phase out for individuals earning more — for each $1,000 in additional income, a person would be entitled to $100 less in credit, meaning a 61-year old could make up to $115,000 and still receive some credit.

But Mermin and other analysts said that most low-income people, regardless of age, receive much higher payments under the current law.

“This new health insurance credit is likely to be less helpful for low-income folks but more helpful for those who currently don’t benefit from the current premium tax credit,” Mermin said.

The plan could also have major impact on people who might want to use Medicaid in the 31 states and the District of Columbia that accepted expanded ACA benefits. Starting in 2020, those states would only receive the full federal reimbursement for people who qualified for the program by that date. The rest of the population would be subject to strict new per-capita caps on how much each state would receive for Medicaid.

3. There may be more tax changes to come. The question of the day in GOP circle is what will happen to a 40 percent tax on expensive employer-provided insurance, known as the Cadillac Tax. House Republicans decided to delay the start of that unpopular but valuable tax from its scheduled implementation date of 2020 to 2025.

That five-year delay may not seem significant. But some tax experts say it looks like a convenient way to make the legislation more appealing to conservatives today while hiding a tax increase that could be coming in the future.

It certainly looks like the type of provision you’d put in the bill if you’re worried about long- term deficits rather than short-term deficits,” Greenberg said.

4. All of these tax changes could create a big deficit headache.  Some conservatives would rather see the “Cadillac Tax” disappear entirely — but that would risk violating Senate rules. Republican leaders chose to use a quirk in the budget rules to vote on the health-care law without the threat of a blockade by Democrats. The unusual process means the bill needs only 51 votes for passage — but only if it doesn’t add to the deficit after 10 years.

Adding the Cadillac Tax back in 2025 could help Republicans balance the budget. But only if they don’t decide to delay it again in 2025.

Republicans aren’t exactly denying this might be a budget gimmick. Some GOP lawmakers and staffers have privately acknowledged they’re delaying the “Cadillac Tax” to push the increase off as far as possible without creating an even bigger hole in the deficit.

“We don’t know if that’s going to be in the final combination of this thing or not — there’s still a lot of conversation we need to have,” Sen. David Perdue (R-Ga.) told reporters on Tuesday.

5. Democrats and even some conservatives are skeptical the math will work out in Republicans’ favor. The GOP plan was already under attack from both sides of the political spectrum from the moment it was released. On the one hand, Democrats are betting the GOP plan will fail because the tax changes would cost too much. On the other, conservatives are calling the plan “Obamacare lite” for replacing the old system of tax credits with a new one and leaving intact the “Cadillac Tax.”

Democrats argue that cutting tax hikes on the wealthy and eliminating penalties on employers who don’t provide health insurance — and individuals who don’t buy coverage — makes it impossible to pay for the parts of the law people do like. They say insurance companies will raise prices if there aren’t enough employers offering coverage and individuals decide not to buy insurance. Insurance companies won’t have any other way of paying for expensive benefits.

“This is not an honest or responsible attempt at legislating, but rather a devastating future for millions of hard-working Americans,” said Rep. Richard Neal (D-Mass.) the top Democrat on the Ways and Means Committee. “The Republican repeal bill would give huge tax cuts to the wealthiest Americans – including health insurance companies and their CEOs – while reducing health care tax credits for millions of low-income Americans and seniors.”

Conservatives say they can’t back a bill that leaves any vestiges of Obamacare intact. Members of the influential House Freedom Caucus and outside groups like the Club for Growth all slammed the House GOP plan for replacing old subsidies with new tax credits.

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“It creates a new entitlement through the refundable tax credits,” said FreedomWorks policy analyst Jason Pye said in a statement. “It allows insurance companies to assess a 30 percent penalty on those who don’t keep continuous coverage for 63 days, which is an individual mandate by another name.”