Commercial properties sold last year in the District of Columbia were significantly underassessed, on the average, according to a study prepared by the District of Columbia's Department of Finance and Revenue.

Although the law calls for tax assessments to be 100 percent of the estimated market value, half the 248 commercial properties sold in 1982 that were studied were assessed at 83.2 percent or less of their actual sales price, the study shows.

It also indicates a lack of uniformity in the commercial assessments. Half the assessments analyzed were 18.8 percent or more away from the 83.2 percent median ratio; in other words, half the assesments studied fell within, and half fell outside, a range of 64.4 percent to 102 percent of fair market value. The International Association of Assessing Officials's standards suggest that assessment uniformity has been met if half the assessments fall within 15 percent of the median.

"Uniformity and equity are the standards," says an out-of-town assessor. "If the assessment is supposed to be 100 percent of fair market value and it's at 60, it's way off, but if all the assessments are within, say, 9 percent, then the property owners are being treated equitably," he explained.

"The most important thing is to be close to the market . . . but if all the properties were treated the same even if they were below the fair market value , they'd be treated equitably," the assessor said.

The D.C. study compared the selling prices of properties sold in 1982 with assessments made during 1982, which will be the basis for the real property tax year beginning July 1, l983.

The District came quite close to fair market value in its assessments of residential property. The median ratio of assessment to sales price for single-family homes was 94.1 percent last year. Half the assessments were grouped within 9.4 percent of the median, well within the 15 percent guideline for single-family homes suggested by the professional assessing organization. Their standard is 10 percent for newer and fairly similar residences, an official of the group said.

The relationship of assessments to sales of vacant land was further off, with the study showing that half the properties sold last year were assessed at or below 73.1 percent of their actual sales price. Half the properties' assessments were more than 31.5 percent away from the median. The IAAO standard for uniformity in this category is 20 percent.

The study showing the underassessments comes at a time when the District is desperately seeking additional revenues. Jeffrey L. Humber Jr., director of the D.C. Department of Finance and Revenue, said he doesn't believe that the City Council or the taxpayers expect the assessments to hit 100 percent all the time. "We strive to have an acceptable product," Humber said. "We are very good in residential properties, among the best in the country.

"Our commercial performance is not as good; I think there are some improvements we have to make, but it is not an unacceptable product," he said. "I think most commercial properties will find their assessments fair and reasonable."

Robert King, the department's acting associate director for real property taxes, noted that the District, an urban area with rapidly changing conditions, has a lot of variation in commercial properties, making assessments more difficult. "It's not a simple thing to estimate what someone might pay for a building," he noted.

Seeking to improve its assessment process, King said that the District is developing an assessment manual, has instituted a comprehensive review of assessments, and is in the midst of a comprehensive training program this year.

Meanwhile, several thousand people are expected to have filed appeals of their tax assessments for the coming year with the Board of Equalization and Review. It's too soon to know how many appeals of tax assessments actually were filed this year; the deadline was midnight April 15 and, as with income taxes, an enormous number of people filed their appeals at the last minute. They were being processed and logged in by board staff all week.

According to Samuel C. Reynolds, chairman of the board, a total of 3,625 appeals were filed in 1982, with more than 2,000 coming in the last day.

Last year, a total of 1,662 District property owners--almost 46 percent of those appealing--succeeded in getting their tax assessments decreased through the appeals process. The board sustained the assessments of 1,895, or 52 percent, and actually raised the assessments of another 68, or 2 percent of the total.

The board made some significant changes. Reynolds noted that the board inceased the assessments of 25 commercial buildings an average of $494,792, while it lowered the assessments of 362 commercial buildings an average of $137,979. The board made no change in the assessments of 884 residential properties, raised the assessments of 4 homes an average of $21,662 and lowered the assessments of 719 by an average of $17,856.

Overall, the appeals process cost the District government a net loss of $12.5 million in revenues, Reynolds said.

This year, Reynolds said he has made some changes in board procedures. The 15 members of the board used to hear all kinds of appeals; now they will be divided into five panels of three each so they can develop some expertise in an area. One "commercial" panel will hear nothing but appeals on income-producing properties, he noted.