A few months after the rules governing IRAs were liberalized by the Economic Recovery Tax Act of 1981, I made the following statement in this column: "It is likely that total IRA investments may reach into the tens of billions of dollars a year."

How well did that prediction work out? Well, according to a recent issue of "Credit Union Newswatch," a weekly publication of the Credit Union National Association, credit union IRA deposits had reached $8 billion by the end of the 1983 tax year (April 15, 1984).

At the same time -- just two years after my guesstimate -- CUNA estimates that commercial banks held $35.2 billion in IRA deposits; savings and loan associations, $29.5 billion; investment companies (mutual funds), $13.1 billion; and insurance companies, $11.4 billion.

In addition, the amount of money held in self-directed IRAs (primarily by brokerage houses) is estimated at $16.4 billion. That all adds up to a very impressive $113.7 billion in IRAs of all types -- most of it added since the rules were changed to make IRAs available to virtually all those with earned income.

Can $113 billion be wrong? Sure -- but in this case it isn't. Even if Social Security survives in something like its present form, retirement benefits alone really are not adequate to provide a comfortable life.

So unless you have another rich uncle in the wings who is going to leave you a healthy bequest soon, take advantage of the tax-advantaged retirement savings program offered by your Uncle Sam. Start an IRA program, and try to deposit each year the maximum allowed by the tax laws; a little "penny-pinching" now might make your later retirement years a lot more comfortable.

Q: Q A friend of mine and her husband have been supporting their daughter and son-in-law, neither of whom are able to work. (The daughter had multiple sclerosis.) The parents bought a house trailer for them and pay the ground rent and utilities, medical bills and clothing. They also paid for food until a few months ago, when the children started getting food stamps. Can the parents claim the daughter and son-in-law on their tax return? If so, can they go back and correct previous year's returns, since they have not been claiming them?

As to the first question, the answer appears to be yes. I say "appears" because there are a couple of questions not answered in your letter, although the answers may be inferred.

There are five tests for a dependent; three of these are not unequivocally answered. The first is that neither the daughter nor the son-in-law have more than $1,000 in taxable income for the year. (Food stamps should not be counted for this test.)

Second, the parents must provide more than half the total support each year. For this test, the value of the food stamps must be counted as support provided by the state. But the parents may count the fair market value of the quarters provided, in addition to any money spent on support.

Third, the children may not have filed a joint tax return, unless they had no tax liability and filed solely to request a refund.

From the information you provided in your letter, I would guess that they meet all three of these tests; but in the absence of specific statements, I thought it necessary to mention them.

Assuming that the daughter and son-in-law do qualify as dependents, the parents also may include -- in addition to claiming the dependent exemptions -- all medical bills they paid along with their own medical expenses for the deduction on Schedule A.

And they may go back and correct their tax returns for 1981, 1982 and 1983 by filing a Form 1040X for each year on which they claim the two additional exemptions and any extra medical expense, and adjust their tax liability accordingly. The IRS will send them refund checks for each of the three years.