The Internal Revenue Service in April clamped a lien for back taxes on 38.6 acres of Billy Carter's property here, Marion County records show.

The lien bars the president's brother from selling the land -- part of a $196,080, 58-acre site that includes his home -- and permits the IRS to confiscate the property if Carter and his wife, Sybil, fail to meet a set repayment schedule. The property is in her name.

The Carters signed IRS forms accepting the lien on April 18. Records here do not indicate how much they owe the federal government, and IRS officials handling the case were unavailable. In Washington, an IRS spokesman said the law prohibited him from commenting on disputes with any taxpayer.

"If there is a lien on file, that's the extent of what is public," he said.

One of Billy's close friends, however, said the tax problem offered further evidence that Carter began his controversial involvement with the Libyan government because "he needed to make money."

"That's what he was after," said Georgian Donald J. Carter, who is not related to Billy. "He just needed to support his family."

Billy received $220,000 from the Libyans this year -- $20,000 sometime in January and $200,000 sometime in April, the same month that the IRS put a lien on his property. He has described the payments as installments on a promised $500,000 loan that he said he needed to meet various "debts and obilgations."

The president's brother added in an interview on Tuesday's NBC Nightly News that he had already spent the money, but when asked on what, he said "Bubblegum." He said how he uses the Libyan funds is a private matter.

The forms the Carters signed were 433d notices, which normally signify a mathematical error turned up by IRS computers, sometimes in the taxpayer's favor, but more often in the government's. According to IRS officials, the notices spell out the computer-calculated increase -- or decrease -- in tax liability.

The lien, filed at the courthouse here on April 30, would indicate that the Carters' mistake was not in their favor and that it was a substantial one.

Donald Carter, who runs a Gainesville, Ga., real estate office, say Billy asked him to join the group he took on his first visit to Libya in 1978 -- a trip that Donald Carter said was intended to lay groundwork for lucrative oil import commissions.

But after studying up on Libya, Carter said, he wanted nothing of the trip or the prospective deal -- and urged Billy to pull out as well.

"At first I was interested in it," said Carter, "but when I looked into it I wouldn't have touched if for all the oil in Libya.

"I asked Billy not to go. I told him I didn't think it was good." that it "might embarrass the president. Him being the president's brother, I didn't think it his place to go."

But "he'd already made up his mind to go," Carter said. "He felt like he had his own life to live."

In addition, said Carter, "He needed to make money. He no longer had speaking engagements. He didn't have any income. He just wanted to do some importing."

Carter said Billy's relationship with the president, involvement in the financially tangled Carter family business interest and ties to Libya had made it almost impossible for him to get bank loans.

"Banks don't lend to Billy anymore because it invites trouble from the bank examiners," Carter said. "He couldn't walk into a bank and get a loan now anywhere."

As a result, Donald Carter said, Billy needed his help to get a $30,000 loan from the Gainesville National Bank in July 1978. He said that in early 1979 he paid half the balance of the loan when Billy fell behind on his payments, and that Billy later reimbursed him.

In March 1979, Donald Carter made his own $25,000 loan to Billy, according to records. Carter said Billy paid him 10 percent annual interest on the money and repaid him in full in April 1980, around the time Billy Carter got the $200,000 check from the Libyans.

Donald Carter said Billy used the loan "to clean up some of his debts" before entering the Long Beach naval hospital's alcohol treatment center.

Carter said he though Billy "made a mistake, but I don't think he did anything real serious."

"He got in a hurry, I guess, to do something. He didn't exactly know what he was doing. I'm sure he would change if he had to do it over again."

In another development, The Atlanta Journal reported that a Georgia real estate developer claims to have introduced Billy Carter to the Libyans two years ago in hopes of profiting from the relationship.

The developer, Thomas Jordan of Atlanta, said that, in mid-1978, "I was told the wealth of the Libyan state would be at my fingertips if I would deliver the younger brother of the president of the United States to Tripoli, so I delivered him."

Billy Carter flew to Tripoli later in 1978, accompanied by an entourage that included Jordan, state Sen. Floyd Hudgins, and Henry R. Coleman, an old Carter friend.

Jordan told the newspaper they later agreed to establish an agency to represent Libyan business interests in the United States. "We were going to get a commission of 10 percent on all their business in this country," he said. None of the wealth Jordan hoped for ever materialized, the Journal reported.