The IRS failed to test its Obamacare processing system until a week before filing season began, according to a report released today by the Treasury Inspector General for Tax Administration (TIGTA).

“The administration learned nothing from the failed rollout of Obamacare’s website and then repeated the lack of preparation with the IRS and forced that failure onto every American on tax filing season,” said Grover Norquist, president of Americans for Tax Reform.

The agency relies on what is called a Final Integration Test (FIT) to test its ability to deal with potential tax filing complications. However, according to the TIGTA report, the IRS failed to develop and test key systems to integrate Obamacare into the FIT program. As the report notes:

“key systems and programs were not sufficiently developed and tested before delivery to the FIT environment.”

Instead, the process for integration was so chaotic that eight different builds were received, which meant the agency was only able to complete tests at the last minute. As the report notes:

“…the current procedures resulted in the FIT program receiving eight builds of the ACA 5.0 systems with the final build received by the FIT program less than one week before the start of the 2015 Filing Season.”

At the same time, the e-filing system was delivered to FIT with significant errors which increased the risk of processing errors during the filling season. As the report notes:

“Not completing the planned FIT execution on schedule prior to the 2015 Filing Season increases the risk of filing season processing errors that would have been identified and corrected during the FIT.”

In its recommendations TIGTA said that the IRS must ensure timely delivery of systems to the FIT environment. Failure to do so threatens taxpayers’ ability to file returns, receive refunds, and obtain adequate customer service.