U.S. equities failed to hold earlier gains on Wednesday as investors digested President Donald Trump's outline for tax reform, while earnings season continued.

The Dow Jones industrial average closed lower after rising as much as 74.78 points, with Procter & Gamble contributing the most losses. The 30-stock index held about 1 percent away from its all-time high of 21,169.11, however.

The S&P 500 also fell slightly after flirting with an all-time high, with real estate leading decliners. The Nasdaq composite notched an all-time high earlier in the session, but finished marginally in the red.

"The discussion around the tax plan is a positive for the market," said John Conlon, chief investment officer at People's United Wealth Management. But "I don't think the market is excited; I think it takes some pressure off the market, but there are still questions about some of the details."

Major indexes intraday

Source: FactSet

Expectations for lower corporate taxes have been a boon for stocks ever since Trump was elected in November. The S&P has gained 11.6 percent since the election and was on track to post a weekly gain of nearly 2 percent on reignited hopes around lower taxes.

Top White House officials outlined President Donald Trump's tax plan Wednesday, a proposal they said would be the "biggest tax cut" in U.S. history. The proposal slashes the corporate tax rate to 15 percent from 35 percent.

The White House added there will be a "one-time tax" on the trillions of dollars held by corporations overseas. However, Treasury Secretary Steven Mnuchin said the rate for that tax has yet to be determined.

Retail stocks popped on the announcement, as it revealed Trump's plan did not include a border adjustment tax. The SPDR S&P Retail ETF (XRT) rose 1 percent.

It's time for the administration to "go big or go home and a 15% corporate tax rate will certainly make that happen," said Peter Boockvar, chief market analyst at The Lindsey Group, in a note to clients.

"I'll leave it to others to figure out if and how we get there (will obviously be tough) but the implications will have to also be measured by any change in interest rates in response in gauging the impact on corporate earnings and for other obligations," he said.