The administration's admission last Friday—it's always a Friday—that it had sent out 800,000 Obamacare tax forms with mistaken information is merely the latest confirmation that, when it comes to President Obama's signature health law, the White House and its bureaucratic operatives are in way over their heads.

The tax forms, which document tax credits received under the law, were likely to prove daunting to individuals in any case. The administration's rampant mistakes are certain to make tax-season headaches even worse.

The error affects about 20 percent of statements sent out under the law, according to The Wall Street Journal, but individuals who have received the forms have no way of independently determining whether their statement is among the mistaken. As the Journal reports, "It is very difficult for consumers to know on their own whether the local premium listed on the statement, known as a 1095-A, is incorrect." Instead, individuals must rely on the administration, which has already proven itself unreliable, to let them know whether they were among the affected.

The White House downplayed the size of the error, saying that it only affects a "very small fraction" of taxpayers. But even a fraction is still a fairly large number. Close to a million people will have to delay their tax filings as a result of the error, according to the Associated Press, and about 50,000 who have already filed will have to do so again.

The mistakes appear to have occurred when the system used the wrong year's premium to calculate the subsidy amount. How exactly did the system go so wrong? That's a good question, but it's one the administration cannot satisfyingly answer. As Andrew Slavitt, the second in command at the Centers for Medicare and Medicaid Services, which oversees the implementation of the health law, indicated to The New York Times, "officials did not know why the mistake had occurred."

This is not exactly confidence inspiring. But it is telling about the law's intertwining legal and technical complexities, and the ongoing difficulties they present even for the health law's most committed supporters. What this tax-season debacle suggests is that Obamacare is so complicated that even the federal government can't figure it out.