Q: I am having a difference of opinion with the D.C. Assessments Sevices Division about my real estate taxes. I own three adjoining lots, each having a separate tax number. My house is on the middle lot, and we use the two other lots for our children to play in and for our garden.

However, when we received the reassessment for next year, the District permitted me the homestead exemption only for the lot on which my house sits, but not the two vacant lots.

What can I do?

A: The most obvious answer is to petition the District of Columbia government to combine the lots. The District has a form application, which you can fill out, and generally speaking the lots will be combined provided they are contiguous, if ownership of all lots are identical, if all real estate taxes and special assessments are paid, and if application is approved by the city zoning commission.

However, you have raised an interesting and timely question, which prompts me to offer a detailed explanation of the procedure for appealing a tax assessment.

Every year, the District government is required to reassess all 148,796 parcels of real estate. We are taxed on a fiscal year, beginning July 1 and ending June 30 of the following year. Taxes are paid on Sept. 15 for the first half of the year and on March 31 for the second half. There is a stiff penalty for late payment.

Each February, the District usually sends out a notice of property assessment for the following year. The Office of Assessments is obligated to determine the market value of the property, which of course has been going up in the District at a rapid rate each year.

The City Council then establishes a real estate tax rate, which is expressed in dollars per $100 of the assessed value. The current tax rate for residential properties (including condominium and cooperative housing) is $1.54 per $100 of assessed value, and the rate for all other properties is $1.83 per $100.

For example, if your assessment is $61,000, the annual tax would be $939.40. However, the District also has a homestead exemption, whereby if the property is your principal place of residence, $9,000 of the assessment is deducted. Your tax liability then is determined by multiplying this reduced assessment value by the $1.54 tax rate. Thus you would owe only $800.80.

Needless to say, none of us is happy with paying taxes. There is a procedure for appealing the assessment, but you must hurry because the deadline is April 15. If you are unhappy with your assessment, you may appeal to the Board of Equalization and Review, in Room 202 of the District Building, 14th and E streets NW, Washington 20004. (Telephone numbers are 727-6860 or 6861). The appeal forms also can be obtained from any public library.

One should not decide hastily to file an appeal. Before you fill out the form, you should inspect the preliminary assessment role, which is available at the Martin Luther King Library and at selected libraries throughout the city. Bear in mind that the law requires the assessor to evaluate your property on the basis of the market value-and rarely has the assessment caught up with today's prices.

But it is important to determine whether the District has, in fact, inspected your property, evaluated your neighborhood and adequatedly calculated the value of any improvements.

This is a highly specialized area, although it is my personal belief that assessments are often plucked from the air.

If you want to appeal, file your application no later than April 16 (the 15th is a Sunday this year) and you will be notified of a time and date for a hearing. The Board of Equalization and Review is an independent administrative body composed of 15 members appointed by the mayor with the approval of the City Council.

A word of caution: The board is required to raise or lower the assessment of any real property that it finds to be more than 5 percent above or below the estimated market value of the property as determinted by the assessor.By filing your appeal, you run the risk that the assessment will be increased, rather than lowered.

Finally, it seems to me that our advisory neighborhood commissioners should be taking an active role in assisting taxpayers in understanding this very important issue.