Your tax-cut gain may be small, but it can still be invested

For many people, the latest 10 percent cut in federal income taxes might be summed up by a favorite line from Garfield, the curmudgeonly cat of the comic pages: ''Big hairy deal.''

Depending on the number of exemptions they have, the tax cuts that went into effect July 1 will give moderate-income people approximately 2 to 12 extra dollars a week.

For many workers, however, the increases will not make up for past inflation. The tax cut may also be wiped out by higher social security taxes. On top of this, many state and local governments will be trying to make up for cuts in federal assistance with new taxes of their own.

So a federal tax cut may not make much difference in your life. Then again, you may be in a position to save some of the extra cash rather than pay off bills. In a recent poll by the New York Times and CBS News, 42 percent of those questioned said they planned to save the money gained from the tax cut. Fifty percent said they would be spending it, while 2 percent planned to do a little of both. The rest weren't sure how they were going to use their windfall.

If you are among that 42 percent, there are a few ways to save small amounts of money and sometimes even earn respectable returns. In some cases, a few hundred dollars will be needed to open the accounts, but you can add any amount after that.

Coincidentally with the tax cuts, many banks and savings institutions are advertising new certificates of deposit with 91-day and 42-month maturities. These CDs were introduced on May 1, and many banks have been quite aggressive in their efforts to come up with the most attractive instruments. It makes this a good time to shop around.

At Ameritrust Bank in Cleveland, for instance, $500 can purchase a 42-month ''small saver'' CD with interest pegged to the 91-day US Treasury bill rate. Last week, said Joyce Enterline, a spokeswoman, the CD was paying 13.269 percent , a rate that will change every month through the life of the certificate. People buying it are not ''locked into'' the same rate for 31/2 years. Subsequent additions of at least $100 can be made to the account during that period.

Another 42-month CD is offering a slightly higher rate, but it is fixed for the entire term. So if you think rates are going to go down and stay down for a while, you may want to lock in current high rates with one of these certificates. If interest rates rise instead, then you will be left behind. The minimum deposit on these CDs is also $500, and you cannot add to it.

Any discussion of small savings plans offered by banks or thrifts should not omit that old standby, the passbook savings account. True, they only pay 51/2 percent interest right now, and until recent months this was well below the inflation rate. But for those who have no savings, a passbook can be a good way to build up the $500 needed for a CD or the minimum needed to open an account at a money market mutual fund.

Although money fund interest rates have dropped to the 13 percent range in recent months, they remain one of the easiest and most flexible ways for people to set aside small amounts of money and get a good return. While most funds have minimum initial deposits of $1,000 or more, there are a few with $500, $250, or if you like. You can find out which funds have the lowest entry requirements, the smallest subsequent deposits that can be made, and their addresses by sending $15 to Donoghue's Money Fund Directory, Box 540, Holliston, Mass. 01746.

Another old standby that, like the passbook savings account, has taken a lot of criticism in recent years has made some improvements that make it worth investigating. The US savings bond may be the easiest program for small savers to put money into. Many employers will take the money for savings bonds out of your paycheck before you even see it. This payroll deduction feature has always been available. What is new is a 9 percent interest rate on Series EE bonds. You pay $12.50 for a $25 bond, for instance, and in eight years, it doubles its worth to pay face value. The same 50 percent discount is available for eight other denominations up to $10,000, including $50, $75, and $100 bonds.

Alvin Hattel, a spokesman for the Savings Bond Program, says there is a proposal to allow the Treasury to apply a variable rate on the bonds. The interest rate would ''float'' and pay 85 percent of the interest being paid on Treasury bills. The proposal, however, has not yet been approved by Congress.

Many credit unions also offer payroll deduction plans. And they pay higher, more competitive interest rates than they did a year ago.

Finally, this might be a good time to think about starting an individual retirement account. IRAs are offered by banks, brokers, insurance companies, and mutual funds, and depositors can often add as little or as much or as they like.

If you would like a question considered for publication in this column, please send it to Moneywise, The Christian Science Monitor, One Norway Street, Boston, Mass. 02115. No personal replies can be given by mail or phone. References to investments are not an endorsement or recommendation by this newspaper.