NEW YORK (AP) _ For many accountants around the nation, this is the tax season of their discontent.

A cloud of new codes and forms and temporary regulations - all courtesy of the 1986 tax overhaul - has pushed some seasoned professionals to the brink of early retirement, experts in the field say.

''The (tax) requirements have made a joke out of the word 'simplification,' 3/8' ' exclaimed Stephen Buschel, partner in charge at Seidman and Seidman-BDO's office in White Plains, N.Y.

Itemizing, calculating interest and searching for that extra deduction require significantly more effort this time around - anywhere from 10 percent to 50 percent more to figure an individual return, according to the American Institute of Certified Public Accountants. The Internal Revenue Service itself estimates it will take from 48 minutes to one hour and 12 minutes to complete individual new forms. And that's only if the taxpayer ''is not starting from scratch,'' said IRS spokeswoman Johnell Hunter.

The estimate does not count the time spent ''collecting data and reading the forms,'' she said, which include never-before-seen documents for reporting home mortgage interest, non-deductible Individual Retirement Accounts, passive losses on tax-sheltered investments and unearned income for children under 14.

Individual accountants would have to scale an Everest of paper if they did every bit of tax law reading themselves. The government's general explanation of the law is 1,300 pages alone, noted Sidney Kess, a partner in the New York office of Peat, Marwick, Main & Co.

Instead of cracking all the books themselves, accountants have been flocking to seminars to gain a streamlined version of the changes.

Short courses for accountants on the new law have played to full houses nationwide. Kess, who recently visited about 50 cities to update nearly 10,000 certified public accountants, said that was the largest registration he had ever seen for his two-day seminars.

''It reflects the times,'' he said. CPAs ''are anxious to get as much help as they can.''

But what's most troubling is that accountants emerged from the explanatory meetings with ''more questions than answers,'' Kess said.

''All of a sudden we're facing specific problems on the rules, and no matter how much you read and go to courses, you look at a specific client and find 80 percent of the questions weren't really answered,'' said John Bryant, coordinator of tax services at McGladrey & Pullen's office in Cedar Rapids, Iowa.

The reaction of many accountants has been: ''It's time to retire,'' Kess said. ''And some were serious,'' he added.

The IRS is spewing out a continuous stream of ''temporary regulations,'' or explanations, some numbering hundreds of pages.

The burden is particularly crippling for the accountant who works alone. At larger firms, individual accountants often are tapped to develop expertise in single, narrow aspects of the tax code, so that the firm has a good collective grasp of the changes.

''The sole practitioner is at a disadvantage more than ever - he has the same responsibility to his or her clients as we do,'' Buschel said. ''I just don't see how they're able to keep up.''

Some haven't.

''We've had mergers with some small firms - sole practitioners - and although the stated reason wasn't the tax law, you get the sense that they just threw up their hands at it,'' said McGladrey & Pullen's Bryant.

McGladrey & Pullen is one national firm that has asked some of its CPAs to develop expertise in given areas.

''Our specialists are spending up to a half day on the phone answering questions'' from other accountants within the firm, Bryant said.

At H&R Block's office in Whittier, Calif., tax preparers have received 40 hours of instruction on the new tax rules, said district manager Maria Bennett. ''It's almost as much as the whole training course,'' she said, referring to the 45 hours of instruction it takes to become an H&R Block tax preparer.

It remains to be seen whether accountants will make significantly more money because of the tax law changes. Many are quick to note that although they will bill more hours on individual returns, they can work only so many hours a week.

Some accountants are hiring more preparers to handle the increased workload, while others will ''be more selective on how many new clients (they) will pick up,'' Kess said.