President and Mrs. Reagan released returns Friday showing they paid $86,638 in federal income taxes last year on adjusted gross income of $345,359.

Documents released by the White House as the Reagans vacationed at their mountaintop ranch showed the first couple paid $5,822 less in taxes on $8,719 in additional income over 1986.In addition, the Reagans were due $10,754 refund for 1987, which they designated to be applied to their estimated taxes for 1988.

In addition to his $200,000 salary, Reagan reported a slight increase in rental income from air traffic navigation facilities located on his 688-acre ranch and $46,208 in capital gains, which the White House has attributed in part to the sale of drawings inherited by the first lady.

The Tax Reform Act that lowered income tax rates for the Reagans and other Americans also took away many long-time deductions used to lower tax bills in the past.

The Reagans claimed $77,792 in deductions for tax payments, personal interest, charitable contributions and other expenses.

Their $25,407 in contributions included $11,312 to Eureka College, the president's alma mater, and $214 to the Community Foundation of Greater Washington, which represents the amount Mrs. Reagan received in royalties from reruns of two television shows on which she made guest appearances to promote her campaign against drug abuse.

The Reagans signed their tax return Wednesday after meeting with their lawyer, Roy Miller. It was mailed to the Internal Revenue Service Center in Fresno, Calif.

Meanwhile, White House chief of staff Howard Baker said the Reagans made sure "all of the i's were dotted and the t's were crossed" before leasing a $2.5 million Los Angeles home purchased by friends.

The White House, which has made only a limited disclosure of the terms of the three-year lease the Reagans signed effective March 1, said that before buying the three-bedroom, six-bath house, the prospective owners, most of them friends of the Reagans, sought an opinion on the propriety of the deal.

It said the opinion concluded that the Reagans would comply with standards of conduct regulations and conflict of interest statutes if they paid a fair-market rental or purchase price.