* Technology, healthcare lead the advance
* Trading volume hits highest level since June
* S&P, Dow post for fourth straight week of gains
* Indexes up: Dow 0.58 pct, S&P 0.9 pct, Nasdaq 1.17 pct (Updates to close, adds commentary, volume numbers)
By Sinead Carew
NEW YORK, Dec 15 (Reuters) - Wall Street's three major indexes climbed to record closing highs on Friday with broad-based gains as a long-awaited bill to cut corporate tax rates looked like it would win enough support from lawmakers to pass.
U.S. congressional Republicans were expected to release final details of their plan late on Friday, with decisive votes planned for next week after lawmakers who had previously criticized the bill started to voice their support.
Republican Senator Bob Corker joined Senator Marco Rubio in signaling support in the late afternoon. Rubio had criticized the initial proposal, saying it did not give enough tax relief to working families, while Corker, had expressed concerned about the bill's impact on the federal deficit.
The bill is expected to drop corporate tax rates to 21 percent from 35 percent and some investors are betting that companies will put most of the savings toward a boost in shareholder payouts.
"It's meaningful in terms of its impact on shareholders. You're going to see an increase in stock buybacks, maybe some dividend payouts," said David Joy, chief market strategist at Ameriprise Financial in Boston.
"By and large there's a high correlation between higher equity prices and consumer confidence and consumer spending. Some translates into rising consumer sentiment and better feelings about job security," he said.
However, as the tax package has evolved, it has tilted increasingly toward benefiting businesses and the wealthy, a trend that concerned some lawmakers.
The S&P was up 1 percent after Corker announced his support, but couldn't sustain those levels as investors awaited tax bill details, according to Brian Battle, director of trading at Performance Trust Capital Partners in Chicago.
"We don't know how stimulative it will actually be," said Battle. "There shouldn't be any surprises. The stuff they were apart on seems manageable."
The Dow Jones Industrial Average rose 143.08 points, or 0.58 percent, to 24,651.74, the S&P 500 gained 23.8 points, or 0.90 percent, to 2,675.81 and the Nasdaq Composite added 80.06 points, or 1.17 percent, to 6,936.58.
The S&P 500 and the Dow closed higher for the fourth week in a row, while the Nasdaq saw its first weekly gain out of three.
The S&P's Energy index was the only one of its 11 majors in the red with a 0.03-percent dip. Technology and Healthcare indexes led the advance with 1.24 and 1.17 percent gains, respectively.
The S&P financial index closed up 1.04 percent, paring earlier gains. Banks are seen as one of the biggest beneficiaries of tax reform.
The S&P consumer staples index rose 1.12 percent. Costco was its biggest percentage gainer, up 3.7 percent, after the retailer reported upbeat results.
CSX tumbled 7.6 percent. The railroad said its Chief Executive Hunter Harrison was taking medical leave amid its controversial turnaround plan.
"Quadruple witching," the simultaneous expiration of U.S. options and futures contracts for stocks and indexes, boosted volume to 10.7 billion shares, well above the 6.73 billion average over the last 20 trading days, and the highest since a year ago.
Advancing issues outnumbered declining ones on the NYSE by a 2.24-to-1 ratio; on Nasdaq, a 2.32-to-1 ratio favored advancers.
The S&P 500 posted 37 new 52-week highs and 1 new low; the Nasdaq Composite recorded 85 new highs and 54 new lows.
Additional reporting by Rama Venkat Raman and Sruthi Shankar in Bengaluru; Editing by James Dalgleish and Nick Zieminski