Question: Why do so many people buy a mutual fund that charges a commission? It seems to me that I will always do better in a no-load fund, because all of my money is working for me.

Answer: What you say isn't necessarily true. If you check the various independent annual fund comparisons, you will find that load funds -- those on which a sales charge is levied -- often lead the list.

What is true is that a no-load fund whose performance over the years is equal to a given load fund should show better net results because there has been no deduction from the amount invested.

The problem, of course, is to pick a no-load fund that will perform that way. The key is management "smarts" rather than the presence or absence of a sales charge.

In that connection, let me stress a warning -- the same warning that mutual funds of either type generally attach to their presentations: Past performance provides no assurance of future results.

To get to your question: More money is invested in load funds, because people don't generally "buy" mutual funds -- they are "sold" mutual funds. And no-load funds offer no commission incentives to brokers.

To buy a no-load fund, an investor must take the initiative -- must respond to a newspaper or magazine ad, study the prospectus and make his or her own decision.

If you go to an independent financial adviser, you can get assistance in selecting a no-load fund -- but you generally will pay a fee for that service. You can't really expect a representative in a brokerage house, whose living is derived from sales commissions, to push a no-load fund, which pays no commissions.

Q: My husband died in 1979, and this year for the first time I'll be filing a separate tax return. My income will consist of a survivor's pension, social security and some interest on CDs. Am I required to file estimated tax or can I pay it all next winter?

A: Without having the numbers in front of me, I can't really tell; but from your letter I assume you will have some tax liability for 1980.

If you expect to owe more than $100 in federal income tax, then you should have filed an estimated tax return (IRS Form 1040-ES) by April 15; and you should be making quarterly payments based on that estimate.

Add up your anticipated 1980 pension payments and the bank interest you expect for the year. (Social Security is not taxable). Then figure what the tax would have been using the 1979 rules. (My guess is that the tax reduction being talked about by the several political candidates won't be effective until next year.)

You can then file a 1040-ES by Sept. 15. Send in half the estimated tax liability with the return; then pay the other half by Jan 15.

Possible alternative: If the payers of your survivor's annuity withholds tax, ask them to take out enough in the remaining months to cover the full tax liability. (Next January be sure to reduce the amount withheld from each check to distribute the total over the full year.)

Maryland, Virginia and the District all have similar pay-as-you-go requirements, so you must go through the same exercise for your state income tax liability.

Q: Can I name anyone I want as a beneficiary of my life insurance policy? I've heard there are restrictions.

A: There are no restrictions on the selection of a beneficiary for your life insurance. You can even name your estate -- which makes it possible to specify the distribution in your will.

But there are restrictions on who can own the policy. To own a policy on another person's life, you must have what is called an "insurable interest" in that person.

That means that you have either some reasonable expectation of benefiting from the insured person's continued life or a probability of economic loss in the event of his or her death.

A simple test for insurable interest is either a family connection (by blood or marriage) or a financial relationship such as a business partnership.