US Vice President and Democratic presidential candidate Kamala Harris' proposed corporate tax hike ahead of the November Presidential elections could lower earnings for companies on the benchmark S&P 500 index by about 5%, analysts at Goldman Sachs said.

Last month, Harris proposed raising the corporate tax rate to 28% from 21% and ensure "big corporations pay their fair share," if she wins the election against Republican rival Donald Trump.

Goldman estimated that at a 28% taxation rate earnings of S&P 500 companies would take a 5% hit.

Adding taxation of foreign income and an increase in the alternative minimum tax rate to 21% from 15% could reduce earnings by as much as 8%, the analysts said in a note dated Wednesday.

On the other hand, Trump's proposed relief on the federal statutory domestic corporate tax rate to 15% from the current 21% would "arithmetically" boost S&P 500 earnings by about 4%.

"The current US statutory corporate tax rate on domestic income is 26%, but the total effective tax rate paid by the typical S&P 500 company is 19%," the brokerage added.

Goldman projected with each one percentage point change in the US statutory domestic tax rate the shift in S&P 500 earnings per share (EPS) would be slightly less than 1% or about US$2 of S&P 500 EPS.

Harris' rise to the top of the Democratic ticket has reenergised a Democratic campaign that had harbored doubts about President Joe Biden's chances.

On Wednesday, she took aim at former President Trump saying his plans would cut off federal programs that offer loans to small businesses, cut the corporate tax rate and push the US deficit higher.

Polls showed that Trump had built a lead over Biden but Harris has since edged ahead of the Republican candidate in some national opinion polls.

  - Reuters