Three years ago, Congress bailed out the troubled thrift industry by creating net worth certificates -- or paper IOUs issued by the federal government to savings institutions. The object: a quick fix for financial statements.

The law authorizing that temporary remedy for industry financial woes will expire Oct. 15, unless Congress acts to renew it -- which appears far from certain at this point. Although industry officials say they would like to see the authority renewed, its potential lapse appears unlikely to create major problems for them.

Under the terms of the Depository Institutions Act of 1982, better known as Garn-St Germain after the congressional banking committee chairmen who co-authored it, thrift institutions considered viable by federal regulators could receive noncash assistance to stay solvent. The assistance was in the form of government promissory notes good for three years.

If the authority lapses, no additional thrifts may draw net worth certificates. But savings associations that already have them will find their situation essentially unchanged. Existing certificates need not be repaid until institutions become profitable again.

The Federal Home Loan Bank Board estimated in May 1982 that 1,500 savings institutions would qualify for assistance through net worth certificates. The figure was later reduced to 500. A General Accounting Office report found that the program was underutilized because savings institutions didn't want to appear to be wards of the government, the GAO found.

According to the latest FHLBB statistics, 106 savings institutions insured by the Federal Savings and Loan Insurance Corp. hold $144.7 million in net worth certificates. That amounts to about 3 percent of the 3,196 FSLIC thrifts, which have a collective net worth of $42.3 billion.

The chief beneficiaries were New York's mutual savings banks. Of the 25 savings banks that hold $682.7 million in net worth certificates, 22 are located in that state. They continued to draw on the program until June of this year, an FDIC spokesman said.

However, Jim Butera, vice president for legislation and regulation of the National Council of Savings Institutions, said he does not know of any savings banks that are drawing down new certificates now that the industry generally has returned to profitability. The trade organization nevertheless supports renewing the program in case interest rates go back up again and threaten the thrifts' viability.

The U.S. League of Savings Institutions urges a three-year extension. The FDIC, which originally opposed net worth certificates, has not taken a position this time around.

Renewal provisions are contained in comprehensive banking bills pending in both houses of Congress. Since there is little chance of major legislation passing by Oct. 15, separate net worth bills have been introduced.