President Reagan and his wife, Nancy, paid $122,703 in federal income taxes for last year, or 31.1 percent of their adjusted gross income of $394,492, according to tax returns made public yesterday by the White House.

The Reagans are due a refund of $26,907, which they applied to next year's tax bill, the returns show. The president had $69,610 withheld from his paycheck and $80,000 paid in advance from last year's refund.

In addition to the president's $200,000-a-year salary, the Reagans reported interest income of $115,906; dividends of $4,462; capital gains of $18,827; pensions, $28,091; rents, $3,600, and other income of $22,834, which included a one-time payment of $17,282 in accrued royalties on Reagan's autobiography, "Where's The Rest of Me."

Nancy Reagan received $772 in royalties for television appearances on "Different Strokes," a situation comedy, and "One to Grow On," an advice spot for children. White House spokesman Larry Speakes said the First Lady donated these royalties to charity.

The couple's income dropped from last year's $440,657 largely because of a major fall-off in dividends, which totaled $86,676 in 1984. Speakes attributed this to changes in the president's blind trust, which may have shifted into securities that do not pay dividends or into tax-exempt investments.

After taking office in 1981, Reagan put his non-real estate holdings into a blind trust so as to avoid conflict of interest in decisions that might affect his wealth.

Reagan deducted $23,298 in charitable contributions, including $10,798 in cash, for which recipients were not specified; $7,500 to his alma mater, Eureka College; and $5,000 to Northwestern University Medical School for a professorship in surgery named for Nancy Reagan's parents, Loyal and Elizabeth Davis. The late Loyal Davis, Nancy Reagan's stepfather, a neurosurgeon, taught at Northwestern.

Reagan's charitable contributions on last year's returns totaled $20,616.

The president and First Lady deducted $33,956 for state and local income taxes -- a benefit that Reagan has sought to eliminate in his tax-overhaul plan.

Reagan also deducted $33,000 in legal fees paid to Gibson, Dunn & Crutcher, the Los Angeles law firm that handles his business and personal matters.

The return also showed that the Internal Revenue Service challenged an item in Reagan's blind trust last year and that the Reagans paid $167 in interest on the underpayment. Details were not disclosed.

They also reported a long-term capital gain of $119,080 on a final payment for the Pacific Palisades home in Southern California they sold after coming to the White House.

Reagan, as in the past, did not check off the $1 contribution to the presidential election fund.