Here are the principal provisions of the Economic Recovery Tax Act of 1981 that apply to individual taxpayers, along with the effective dates for each. (Caution: "1982" refers to the tax year, not to the 1981 return you are now preparing.)

Tax rates. Maximum tax on all income, regardless of source, dropped from 70 percent to 50 percent on Jan. 1, 1982. Tax brackets are adjusted to reflect a tax reduction of 1 1/4 percent for 1981, approximately 9 percent in each of the next two years and, finally, another 4 percent for the 1984 year -- a total of about 23 percent.

Capital gains. The new 50 percent tax ceiling on all income translates to a maximum tax on long-term capital gains of 20 percent, down from 28 percent. (Only 40 percent of a Long-term gain is subject to tax.) The 20 percent ceiling was made retroactive to June 10, 1981.

Tax indexing. For tax years after 1984, tax rate brackets, personal and dependent exemptions and the zero bracket amount (the old standard deduction) are to be adjusted annually to reflect changes in the cost-of-living index.

Two-earner couples. To reduce the "marriage tax penalty," couples can exclude 5 percent of the first $30,000 of earned income of the lower-earning spouse for 1982. Starting in 1983, the exclusion goes to 10 percent of the first $30,000.

Overseas employes. In 1982, U.S. taxpayers living and working abroad who meet certain conditions can exclude foreign earned income up to $75,000. The exclusion goes up $5,000 each year until it levels off at $95,000 for 1986 and later years. An additional exclusion is permitted for "excessive" living costs.

Sale of residence. The waiting period to roll over a gain on the sale of a principal residence into a replacement is extended from 18 to 24 months. The new rule applies to sales after July 20, 1981; earlier sales for which the rollover period had not expired on that date get a six-month extension. One-time exclusion of gain by a person 55 or older jumped on the same date from $100,000 to $135,000.

Dependent care. Starting in 1982, the expense ceiling goes up to $2,400 for one dependent, $4,800 for two or more. The percent allowance is higher, too, but tied to an income test, with a 30 percent maximum for those with AGI up to $10,000.

Contributions. Taxpayers who don't itemize may still deduct a part of their charitable contributions. For 1982 and 1983, you may claim 25 percent of the first $100. (Both the rate and the dollar limit go up for later years through 1986, after which it expires.)

All Savers Certificates. A one-time exclusion of up to $1,000 ($2,000 on a joint return) of interest income is offered for one-year certificates of deposit issued by banks and savings institutions during the period Oct. 1, 1981 to Dec. 31, 1982. The rate is pegged at the time of issue to 70 percent of the latest yield on one-year T-bills; once issued, the return remains unchanged for the full one-year term.

Utility dividends.For tax years 1982 through 1985, taxpayers may exclude up to $750 a year in certain utility stock dividends when issued in the form of new shares as part of a dividend reinvestment plan.

Interest exclusion. Under earlier rules, taxpayers may exclude up to $200 ($400 on a joint return) of combined interest and dividend income. The new law restricts this provision to 1981 returns only. For tax year 1982, the rule reverts to the earlier exclusion of $100 ($200) for dividends only. There is a new and complex interest exclusion scheduled for 1985.

Retirement saving. Starting Jan. 1, 1982, IRAs are made available to all earners, including those covered by a pension program at work or by a Keogh plan for the self-employed. On the same date, the annual IRA ceiling went to $2,000 ($2,250 for a spousal plan) with no percent limitation. Keogh and Simplified Employes Pension Plan (SEPP) limits remain at 15 percent of earnings but the dollar ceiling doubles to $15,000. Divorced persons may continue contributing (from alimony or earnings) to a spousal IRA established at least five years before the divorce.

Adoption expenses. Effective for 1981, a taxpayer may claim up to $1,500 as an itemized (Schedule A) deduction for expenses in connection with adoption of a "child with special needs."

Commodity straddles. Technical changes to the rules on commodity futures contracts remove some of the year-end tax advantages formerly available.

Business expenses. An individual who operates a business that is reported on Schedule C has some new tax breaks to watch for. Accelerated depreciation applies to property acquired in 1981 and later years. Starting in 1982, some normally depreciable property may be written off as an expense subject to annual dollar limits.

Estate and gift tax. The unified estate-gift tax credit goes up each year, starting in 1982, until it reaches an equivalent exclusion of $600,000 in 1987. This will effectively eliminate perhaps 99 percent of estates from federal tax. Beginning in 1982, unlimited gifts and bequests may be made to a spouse tax-free. The annual per-donee exclusion on gifts to others goes to $10,000 ($20,000 if both spouses concur) from the present $3,000 ($6,000) limit.