What was going on when I was born?

Your TaxesA Guide to Preparing 1980 ReturnsEleventh of 12 articles.- By DEBORAH RANKIN Even though the Internal Revenue Service has made a serious effort in recent years to simplify the tax forms, the tax code is so complex - it runs to some 6,000 pages of fine print - that many people relegate the chore of preparing their return to someone else. One result is a flourishing tax preparation industry that grosses as much as $1 billion a year. In 1980, 39 percent of the 88.8 million individual tax returns filed were completed by paid preparers, according to the I.R.S. The industry includes a wide range of preparers, from certified public accounts, who generally provide the most knowledgeable and comprehensive tax assistance, to fly-by-night operators who put out a shingle in January and disappear on April 15. Professional Help People whose financial lives are complex - for example, those with capital gains, income from a business or trust, or tax shelter losses - frequently turn to certified public accountants, or C.P.A.'s. C.P.A.'s generally are college graduates who have passed a complex four-part examination administered by the American Institute of Certified Public Accountants and have spent several years working for a recognized accounting firm. They are automatically entitled to represent taxpayers in audit disputes before the I.R.S.

New York City schools are closed today in observance of Lincoln's Birthday, and schools throughout the metropolitan area will be closed Monday for Washington's Birthday.

Administration economic officials said today that a struggle between two groups of advisers had ended with a decision to base budget revenue and spending projections to be released next week on a relatively conventional economic outlook. The officials said that Murray L. Weidenbaum, chairman of the Council of Economic Advisers, and the budget director, David A. Stockman, jointly concluded that basing budget projections on a far more optimistic forecast for the economy, one prepared by the Claremont Economic Institute, a group of ''supply-side'' consultants, would divert attention from the projections to whether the forecast was realistic. The debate and decision over which numbers to use illustrated anew the tensions within the Reagan Administration between two groups of economic advisers. One, the ''supply-siders,'' is convinced that the Reagan program of budget and tax cuts will lead to dramatic improvement in the economy. The other, a more traditional group, is less optimistic and believes in more restraint in public pronouncements about the economic outlook.

An article in Business Day last Friday misstated the extent to which price controls on natural gas have been removed. Only four types of gas, including that from wells below 15,000 feet, have so far been decontrolled. All new gas and some old gas will be decontrolled in 1985, but most old gas will continue after 1985 to carry some price limitation.

Lenders are restricting credit to individuals as consumer-loan losses increase at U.S. banks, finance companies and retail operations. Those in the lower-income brackets or without real estate to use as collateral will find credit especially difficult to get. Lenders attribute the losses to last year's combination of recession and inflation and to a 1979 bankruptcy law that raised the amount of property individuals can protect against seizure by creditors. (Page A1.) The Administration will present a gloomier economic picture than it had intended when it offers budget projections next week. A pessimistic forecast would focus attention on the proposals, not on whether the forecast was realistic, officials said. Separately, Murray L. Weidenbaum, chairman-designate of the Council of Economic Advisers, expressed skepticism that the budget could be balanced by 1983, as the President has committed himself to doing. (D1.)

From his top-floor office, the chairman of the Export-Import Bank looks out over the wintry green of Lafayette Park and across Pennsylvania Avenue to the White House. This proximity to power has been of little help to the bank. It is one of the targets on the austerity hit list of David A. Stockman, director of the Office of Management and Budget and a powerful force behind President Reagan's drive to reduce the growth of Federal spending. Much to the distress of fellow Republicans in the international business community, Mr. Stockman says the Export-Import Bank, which helps finance American exports by making loans to foreign buyers, is lending too much money. He wants to cut its operations by 20 percent in the current fiscal year and another 20 percent in the year beginning next Oct. 1.

WHEN Deborah Harry of the popular rock group Blondie made a television commercial recently for a jeans manufacturer, she was indulging in utter fakery. The camera followed her through a fake loft district and into a fake Bohemian nightspot, where John Lurie, who leads a New York combo called the Lounge Lizards, was playing fake jazz on his saxophone. The Lounge Lizards, who will be performing tomorrow night at the Squat Theater, 256 West 23d Street, are leading purveyors of an esthetic of the fake. At this point it is mostly a New York phenomenon, but the esthetic of the fake has penetrated the top of the country's pop charts as well. There has always been a certain amount of fakery in rock. Elvis Presley was a fake guitarist; he knew how to play the instrument, but found that it was more effective slung over his shoulder as a prop. Most rock performances these days are carefully orchestrated set pieces that give the illusion of spontaneity, but which are repeated exactly night after night. In most instances, the groups are capable of improvising, but have found that predictably exciting shows are good business.

Standing amid the rubble on a lot near the South Brooklyn waterfront yesterday, Mayor Koch announced a city-sponsored program for the construction of 2,200 moderately priced one-family and twofamily houses in 10 impoverished neighborhoods. The Mayor said that construction would start in the spring or early summer, and that the houses would be ready for occupancy by mid-1982. Construction costs and mortgages are being financed by Federal housing funds.

A Federal District judge in Dallas said today in a preliminary ruling that the Federal Government had no power to seize $3 billion in Iranian assets still frozen in the United States. The ruling by Judge Robert W. Porter could raise major legal obstacles to enforcement of crucial provisions of former President Carter's hostage agreements with Iran. Judge Porter also said the Government could not nullify court orders and terminate lawsuits against Iran, as President Carter agreed to do. Judge Porter ordered Treasury Secretary Donald T. Regan and other Federal officials not to interfere with a lawsuit against Iran by a subsidary of H. Ross Perot's Electronic Data Systems Corporation, to which he awarded a $19 million judgment last May 9. While the judge's order directly affects only that lawsuit, the broad reasoning in his 30-page opinion could affect the entire hostage package.

After meeting with his company's principal stockholder, the Canadian Government, Charles F. Fogarty of Texasgulf Inc. was returning Wednesday to corporate headquarters in Stamford, Conn., from Toronto. Company officials were putting the final touches on an annual report that showed Texasgulf making more money than it had in any previous year. And prospects were for more growth in coming years. It all seemed like business as usual for a company that analysts said had benefited from a long run of good luck. Starting with one of the biggest copper finds in history, the company charged into chemicals, oil and gas and a host of other risky diversifications with almost uniformly good fortune.

''We've realized we're not going to be a city of 12 million people, so we don't have to build high-rise buildings everywhere.'' - Anthony B. Gleidman, New York City housing commissioner. (B3:1.)

A high police official said today that a busboy accused of arson and homicide in the Hilton Hotel fire that killed eight persons had admitted causing the fire but insisted that it had been done accidentally with a marijuana cigarette. The suspect, Philip Bruce Cline, a 23-year-old drifter with a previous arrest record, was ordered held without bond at a hearing this morning pending arraignment later on a charge of first-degree arson and eight charges of first-degree murder. Conviction on any of the charges could result in the death penalty. 'Failed Miserably' in Test Lieut. John Connor, chief of the Las Vegas Metropolitan Police Homicide Squad, told reporters this afternoon that the busboy became a suspect after he ''failed miserably'' in a polygraph, or lie detector, test of his initial story that he had discovered the fire Tuesday night while picking up room service trays and had attempted to extinguish it himself.