The Internal Revenue Service said it would delay the 2014 tax-filing season for one to two weeks because the government shutdown disrupted its computer programing and testing.

The season for filing 2013 tax returns likely will start between Jan. 28 and Feb. 4, the agency said. The April 15 deadline for filing won’t be changed, but the agency noted that filers could obtain automatic six-month extensions.

The extra time for the opening of filing season is needed to program and test systems after the government shutdown. The shutdown came during a peak time for systems preparation, the agency said.

The announcement underscores the strains the shutdown placed on some government agencies. About 90% of IRS operations were halted during the shutdown. That put the agency nearly three weeks behind its timetable for starting the 2014 season, the IRS said.