D.C. real estate assessment notices, which usually are sent out at about this time of the year, are being held up by a squabble in Superior Court over what proportion of the taxable property in the District can legally be reassessed this year by the city.

City tax assessors contend that they are under a congressional mandate to adopt an annual reassessment plan for all property by the fiscal year beginning next October. Thus, all 125,000 commercial and residential properties in the city have been reassessed, with most property values rising about 10 per cent over last year, according to Assistant Corporation Counsel Louis P. Robbins.

However, former City Council Chairman Gilbert Hahn Jr., who has successfully challenged city property tax procedures in court before, contends that a citywide reassessment would violate a 1974 Superior Court decision that established a cyclical reassessment system.

Under that system, one section of properties in the city is reassessed one year and the remainder the following year. Hahn contends that if the city adopts the citywide reassessment plan this year, it would be unfair to those 75,000 property owners who were reassessed only last year.

Hahn is asking Judge John Garrett Penn to prohibit the citywide reassessment until next year or, if there is to be a citywide reassessment, roll back the reassessments that were imposed last.

If the citywide assessment is carried out, Hahn said yesterday, it will mean tax bills of an additional $50 to $100 this fall for the 75,000 persons whose property was reassessed last year. The assessed value of the property is he base against which the city's tax rate of $1.83 per $100 of assessed evaluation is applied to determine property tax bills.

Robbins said yesterday that he believes the city must abide by the congressional order to reassess citywide by this fall. "No matter when you go to a full-year cycle," Robbins said, "somebody is going to get hit two years in a row."

Judge Penn has asked the city for more specific information on how the reassessments have been carried out and the amount of the increases, Robbins said. A decision by the judge is expected soon after he gets the materials late next week, according to Robbins.

The court action stems from a 1974 suit filed by Hahn in which Judge Penn eventually held that the city had been reassessing some areas more frequently than others and set up the two-year cyclical reassessment plan as a remedy.