President Carter and his wife Rosalynn owed no federal income tax last year but will give the government $6,000 because of Carter's "strong feeling" that people in his income bracket should pay some tax, White House press secretary Jody Powell said yesterday.

Powell released a copy of the President's 1976 tax return, which was filed yesterday, along with a letter to the district director of the Internal Revenue Service in Atlanta asking the IRS to accept the $6,000 voluntary payment.

The return showed that last year Carter had an adjusted gross income of $54,934. After deductions, his federal income tax obligation was $11,675, about 22 per cent of his income. But that obligation was more than wiped out by a $20,864 investment tax credit the President received from the purchase of equipment for the peanut warehouse business he owns with his mother, Lillian Carter, and his brother, Billy.

Although he voluntarily paid $6,000 in taxes, Carter is still due at $20,026 refund from the IRS, according to the return. This is because he made more than $26,000 in estimated tax payments to the government during the year in anticipation of his final tax obligation.

Carter's voluntary 15 per cent tax payment was slightly more than the average federal tax payment by individuals, which has hovered around 14 per cent of income for several years. But it was less than the average tax payment by people of his income who, according to 1975 Treasury Department figures, Paid slightly more than 20 per cent of their incomes in federal taxes.

Powell and White House counsel Robert Lipshutz said the 15 per cent figure was used because that is the amount of the government's so-called minimum tax. The minimum tax, which is not applicable in Carter's case, is applied to income from stock options, capital gains and other special categories that are sheltered from the standard federal income tax.

Asked if the $6,000 payment amounted to "conscience money," Powell replied, "No, I don't think so. It is important to understand that this is an individual who has been releasing his tax returns to be public since long before Watergate, long before it became the thing to do because of one highly publicized incident.

"You are dealing with a fundamental feeling on his part."

Treasury department officials said it is not unprecedented, although certainly unusual, for citizens to make such voluntary payments. The Treasury maintains separate accounts for such gifts, the official said.

Even after wiping out his total 1976 income tax obligation, the President still has $9,189 left from the $20,864 investment tax credit. That amount can be used as a credit against his 1977 income taxes.

Carter did not file his income tax return until yesterday because he had received a routine extension of the April 15 filing deadline from the IRS. Even When he thought the tax forms were ready to be filed, there was another delay last week when Lipshutz raised questions about royalties from his book, "Why Not the Best."

Powell explained that almost $70,000 in royalties was earned last year but not actually paid to the President until January, 1977. He said the IRS advised White House officials that the royalties should be reported as income in 1977.

In May, 1976, Carter promised that all future royalties from his book would be donated to a foundation that is planning a Carter Library near the President's home in Plains, Ga. At last count, Powell said, that amounted to $48,000 of the $70,000 earned last year.

White House officials said Carter owed no income tax because of the large investment tax credit and because his income from the warehouse partnership, which totaled $119,244 in 1975, slipped to $46,555 last year. They blamed the income decline in part on severe winter weather, which they said affected the warehouse's sales of services and supplies.

The Carters also reported $6,674 in income from Carter Farms, Inc., another family business, $919 in dividends and $35 in interest.

The President claimed $13,317 in deductions, including $8,172 in state and local taxes, $447 in interest and $4,507 in contributions - about half of, which went to the Plains Baptist Church.

The return will be audited by the IRS under a new policy to audit the tax returns of Carter and Vice President Mondale for each year they are in office. In addition the IRS is conducting a full field audit of the President's tax return for 1975.

In 1975, Carter reduced his tax obligation from about $58,000 to $17,484 by claiming a similar $41,702 investment tax credit for the purchase of equipment for the peanut warehouse. CAPTION: Picture, President Carter's letter to the IRS asking the agency to keep $6,000 of the more than $26,000 refund duehim. UPI