Residents of Virginia, Maryland and the District of Columbia will have a two-day reprieve from filing income taxes this year because the traditional deadline falls on Saturday.

Federal taxes and state taxes in Maryland and the District of Columbia must be postmarked by midnight Monday, April 17, rather than the usual April 15 deadline. States taxes in Virginia are due as usual on May 1.

Tax assistance offices also will be open extra hours on Saturday. The extended schedule is as follows:

Federal tax assistance in the District of Columbia and suburban Maryland: 9 a.m. to 3 p.m., Saturday, and 8:30 a.m. to 7 p.m., Monday. For information, call 488-3100.

The Internal Revenue Service district Office in northern Virginia at Baileys Crossroads will not be open extra hours, For information, call 557-9230.

Maryland state tax assistance: 9 a.m. to 1 p.m., Saturday, and 8:30 a.m. to 9 p.m., Monday. For information, call 277-1240 in Bladensburg; 568-0222 in Suitland, and 949-6030 in Wheaton.

District of Columbia tax assistance: 9 a.m. to 12 noon, Saturday, and 8:15 a.m. to 7 p.m., Monday, at 300 Indiana Ave. NW. For information, call 629-3324.

The Maryland comptroller of the treasury said the department's phones have been flooded with calls from residents confused about tax legislation enacted by the 1978 General Assembly.

Because of the legislature's action. Maryland residents prohibited by U.S. regulations from itemizing deductions on their federal forms in the past may for the first time itemize deductions on their state returns this year.

Three other new laws will not apply to Maryland residents until next year, however. These are: the bill entitling citizens to tax breaks for child care expenses; the bill increasing the amount of an individual's pension that can be excluded from taxes; and the new provision that raises the minimum income that students must earn to $2.950 before they have to file tax returns.