WASHINGTON (AP) -- When Republicans say they want to lower taxes and get rid of loopholes to make up the lost revenue, they're talking about eliminating some very popular tax breaks enjoyed by millions of people.

That's why making big changes to tax laws is so hard — and why it hasn't been done for 30 years.

Unless Congress simply cuts taxes for everyone, there will be winners and losers, and the losers won't go quietly. If Congress does cut taxes for everyone, lawmakers risk exploding an already large budget deficit.

Republican leaders in the House and Senate say they don't want a tax overhaul to add to the national debt. That's what they mean when they say "revenue neutral." The new system would raise the same amount of tax revenue as the old one, after taking into account some broader economic effects.

President Donald Trump has said he will make public a tax proposal in the coming weeks. Republicans in Congress are also working on plans, with the House GOP taking the lead.

Last year, House Republicans released a blueprint that would lower income tax rates and reduce the number of tax brackets. The gist of the plan is to lower tax rates for just about everyone, and make up the lost revenue by scaling back exemptions, deductions and credits.

A look at the biggest tax breaks enjoyed by individuals, along with The Associated Press' assessment of how safe they are as Congress works to overhaul taxes. All estimates are from the nonpartisan Joint Committee on Taxation, the official scorekeeper for Congress.

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RETIREMENT SAVINGS

Contributions to pension plans are tax-exempt, including defined benefit plans and defined contribution plans, such as 401(k)s. This exemption saved taxpayers $180 billion in 2016, making it the biggest tax break for individuals.

RATING: Safe.

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EMPLOYER-PROVIDED HEALTH INSURANCE

Nearly half of all those in the United States get their health insurance from an employer. The value of those insurance policies is exempt from taxation, saving taxpayers $155 billion in 2016.

Proposals to start taxing at least some health benefits are dividing House Republicans as they struggle to replace President Barack Obama's health law. Some see it as another version of Obama's "Cadillac" tax on high-cost health insurance, which has been delayed until 2020.

RATING: In danger.

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CAPITAL GAINS AND DIVIDENDS

Investors pay reduced tax rates on long-term capital gains and qualified dividends, saving them $131 billion in 2016. The tax rate for investment income is 15 percent for most investors, though the very wealthy pay a top rate of 20 percent. The top tax rate on regular income is 39.6 percent.

In 1986, President Ronald Reagan raised taxes on investments and used the revenue to dramatically reduce tax rates for regular income. Today, few Republicans embrace the idea of increasing taxes on investments.

RATING: Safe, as long as Republicans are in charge.

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EARNED INCOME CREDIT

Nearly 30 million families claimed the earned income tax credit in 2016, which targets low-income working families with children. They saved a total of $73 billion. Republicans like the credit because it rewards work. Democrats like it because it is one of the federal government's largest anti-poverty programs.

RATING: Safe, but there could be changes.

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STATE AND LOCAL TAXES

More than 43 million families deducted their state and local income, sales and personal property taxes from their federal taxable income in 2016. The deductions reduced their federal tax bills by nearly $70 billion. More than 90 percent of taxpayers who itemize take advantage of this deduction. Nevertheless, the House Republican blueprint would repeal it to help pay for lower tax rates.

RATING: In danger.

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MORTGAGE INTEREST

Nearly 34 million families claimed the mortgage interest deduction in 2016, reducing their tax bills by $65 billion. Some economists say the deduction is an inefficient way to promote home ownership. But it has strong support among home owners and every industry associated with buying and building homes. Recognizing the political peril of targeting this deduction, the House GOP blueprint would keep it.

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