There’s plenty of reading to do to understand President Donald Trump’s tax reform proposal, but one major feature is quite simple — a lowering of the federal income-tax rate to 20% from the current 35%.

Trump has heralded the corporate rate cut as a move that would greatly benefit Corporate America, although many U.S. companies currently pay far less than the top 35% rate. However, it is widely viewed as the main reason many multinationals tend to keep a lot of cash overseas, as they are reluctant to repatriate it as long as it would be subject to such a high rate.

Read:Why tax repatriation won’t jolt the U.S. dollar

Related:These are the 5 U.S. companies with the biggest overseas cash piles

We have compiled lists of companies to review what’s at stake as Congress battles over the proposal for the next several months.

Any company’s tax situation can change radically from quarter to quarter or year to year, because of such items as major asset write-downs, gains on sales, realization of deferred tax assets, legal settlements, accounting adjustments or other events. So we decided to use quarterly data provided by FactSet to calculate median effective income-tax rates for the past four quarters.

These tax rates include any state and local income taxes the companies might pay. But regardless of whether a company is paying a boatload of non-federal income taxes, having a high combined effective tax rate means the stakes are high for the companies and their shareholders.

If Trump can make a deal with members of both houses of Congress to slash the corporate income-tax rate, analysts will immediately raise earnings estimates for high-tax companies, which can be reasonably expected to light a fire under the stocks.

Trump's Tax Plan: What You Need to Know

These are the median effective income-tax rates for the 30 companies in the Dow Jones Industrial Average, over the past five reported quarters:

As the table illustrates, seven of the 30 Dow components currently pay less than a 20% tax rate.

To broaden our horizons, we also looked at S&P 500 SPX, -1.11% companies domiciled in the U.S., for which effective tax rate data is available for at least three of the five most recently reported fiscal quarters. Here are the 10 with the highest median effective income-tax rates:

And here are the 10 U.S. domiciled S&P 500 companies with the lowest median tax rates over the past five reported quarters:

If a company’s tax rate is negative, it indicates a net loss, which means the company can carry the tax loss forward to other years and offset income which would otherwise be taxed.

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