President Carter quietly signed the $18.7 billion tax cut bill Monday at Camp David, White House officials announced yesterday.

The tax cut bill was one of six measures Carter signed Monday while relaxing at the presidential retreat. The bill signings were not announced until yesterday, White House officials said, so there could be no criticism of the president for using the actions to influence Tuesday's congressional elections.

Among the other bills Carter signed were:

A four-year authorization extension of federal support for state administered vocational rehabilitation programs, including $808 million for the fiscal year that began Oct. 1. There had been some doubt the president would sign the measure because of its overall $5 billion price tag. Earlier this week, about 150 handicapped people demonstrated in front of the White House to ask that the legislation be approved.

A bill that extensively revises the nation's bankruptcy laws, creating in each judicial district a new bankruptcy court as an adjunct to the existing federal district court. The bill also creates a new category of consumer debtors and establishes for that group, as an alternative to bankruptcy proceedings, procedures for extended repayment of debts under court supervision.

The Surface Transportation Assistance Act of 1978, which authorizes $54.2 billion in spending for highways and mass transit through fiscal year 1982.

A $333 million appropriation for the Nuclear Regulatory Commission that requires various reports be submitted to Congress and establishes conflict of interest standards for agency employes.

Carter also withheld his signature - exercising a "pocket" veto - of legislation that would have authorized special federal payments to Guam and the Virgin Islands to offset local revenue losses that will result from reducion in federal income tax rates enacted in the tax cut legislation. He said the bill was unacceptable "piecemeal approach" to the financial problems of the U.S. territories.

The president had announced his intention to sign the tax cut bill Oct. 26 during a political rally in Miami so his action at Camp David , while withheld from the public for two days, came as no surprise.

The tax cut measure, enacted by Congress the day before adjournment, was a compromise between the House's $16.3 billion version of the legislation and a $29.3 billion Senate version. It contains $12.7 billion in tax cuts for individuals, a $3.7 billion reduction in business taxes and a $2.2 billion cut in capital gains taxes.

Most of the reductions will be effective Jan. 1, but the capital gains provisions were made retroactive to Nov. 1.

White House officials said Carter signed the bill with reservations, believing that too much of the tax breaks in the legislation go to middle and upper-income taxpayers. The measure initially was a vehicle for a number of tax "reforms" sought by the president, most of which were eliminated by congressional committees.

In another development yesterday, Carter briefly answered questions by telephone from an administration sponsored "anti-inflation" forum in Hartford, Conn., promising to "use every legal means at our command" to persuade businesses to comply with the 5 3/4 percent price standard in the anti-inflation program.

"We will be monitoring constantly about 400 or 500 of the top businesses in the country to make sure they do comply," he said. "We will use every legal means at our command to induce them to comply, the arousal of public interest, the awarding of (government) contracts. . ."

The president also promised to submit a "very tight, very tough" budget to Congress next year and forecast that food prices will not increase as dramatically next year as they did in 1978.