Q: Why am I not head of my own household? I am divorced and my children are grown, so I live alone. But I pay all the bills, including mortgage payments and taxes. Why am I in the same tax bracket as a teen-ager living at home with no overhead?

A: The easy answer is that you must be "responsible" for a family member to be considered head of a household for taxpaying purposes. According to the rules, you must maintain a home that is the principal home of an unmarried child, stepchild, adopted child or grandchild; a mother or father who is your dependent (whether or not he or she lives with you) or almost any other relative who is your dependent (not under a multiple-support agreement) and does live with you.

The next obvious question -- and one much more difficult to answer -- is "Why are the rules set up that way?" You have some justification for your complaint; it seems that an adult maintaining a home and paying all the costs of self-support should get a better break than the teen-ager living at home.

I don't have the answer, except to believe that the tax system would be infinitely more complex than it already is if the laws were to be written to cover every possible variation in circumstances.

You might write to your congressman and ask that his or her staff go back to when the "head of a household" category was established; perhaps a clue to the reasoning can be found in the accompanying committee report. And if you get a logical answer, please send me a copy.

Q: My 5-year-old daughter has just started kindergarten at a private school. Can I deduct the cost of the kindergarten as day care? Both my wife and I work, and if our daughter was not in kindergarten she would have to be in some sort of day-care program, as she has been up to now.

A: Yes, the cost of the kindergarten is allowed for the child-care credit (subject, of course, to the limits set in the rules), since the primary purpose of the care is the protection and care of your child while you and your wife are at work.

Incidental education and lunches provided need not be separated from the cost of the kindergarten care; but that will change when your daughter enters first grade. If you were to enter her in a private school then, only the part of the cost that is for her care -- rather than for education -- would be eligible.

However, if she goes to public school and you pay for after-school care or a babysitter, the full amount of that expense would qualify for the tax credit.

Q: I have some custodial accounts (certificates of deposit, mutual funds) for my children. How do I treat them for tax purposes? Do I have to file tax returns for my children who have earned interest on these accounts?

A: As you indicate, the income earned on these custodial accounts is income to the children. You must file a federal income tax return for each child in any year in which the taxable income for that child equals or exceeds the amount of the personal exemption.

For 1984 that amount is $1,000; for 1985 the personal exemption will go up to $1,040 because of tax indexing, which starts next year. (The applicable 12-month increase in the cost of living was 4.08 percent.)

Since you surely will contribute more than half the support for each child, you may continue to claim the children as dependents on your own return. Each child can claim his or her own personal taxpayer's exemption, but may not use the zero bracket amount. (However, any legitimate deductions, such as charitable contributions made from the child's own funds, may be claimed.)

Q: Last year and again this year I called the IRS regarding the $200 dividend exclusion on line 9b of Form 1040 for money market fund dividends. I got conflicting answers. Are those dividends eligible for the exclusion or not?

A: Look at page 9 of the IRS instruction booklet for Form 1040: "Taxable dividends from the following corporations do not qualify for the exclusion. . . . Money market funds, unless the corporation has told you how much of the dividends qualify."

Abramson is a family financial counselor and tax adviser. Questions of general interest on tax matters, insurance, investments, estate planning and other aspects of family finances will be answered in this column. Advice cannot be given on an individual basis. Address all questions to E. M. Abramson, The Washington Post, Business News, 1150 15th St. NW, Washington, D.C. 20071.