The 403-page investigation by the Government Accountability Office was ordered in a provision of the CARES Act, the $2 trillion emergency pandemic aid legislation, which Congress passed in March. So far, $643 billion of this allocation has been spent, the auditors said.

The report noted that as of April 30, nearly 1.1 million payments, totaling almost $1.4 billion, had gone to dead people. According to the G.A.O., the Internal Revenue Service said it did not have the legal authority to deny payment to anyone who filed a tax return for 2019, even if they had since died.

The auditors recommended that Congress give the Treasury Department access to federal death records, to avoid future payments to the deceased.

The report also criticized the C.D.C.’s counting of coronavirus tests, which combines tests for an active infection and those that detect antibodies. This practice inflates the percentage of Americans that appear to have been tested and gives an unreliable picture of the way the virus is spreading around the country, according to the new report. After the C.D.C. was criticized last month for combining the two types of tests in its reports, the agency promised to separate them. But as of June 9, it had still not resolved the issue, the office reported.