Roughly 800,000 Obamacare customers are seeking answers as to why the Obama administration sent them the wrong tax information–a government error that could delay their tax refunds.

California had a similar snafu affecting nearly 100,000 Obamacare customers.

“The errors mean that nearly 1 million people may have to wait longer to get their tax refunds this year,” reports CNBC.

Another 50,000 Obamacare customers who already sent in their tax returns may have to do them over and resubmit them again.

The incorrect tax information sent to the 800,000 Obamacare customers contained the wrong premium information for so-called “benchmark” plan pricing. The bungled government numbers mean some taxpayers may claim too big an Obamacare subsidy and others too little, notes the National Journal.

Obamacare remains deeply unpopular. According to the RealClearPolitics average of polls, just 39% of Americans support Obama’s signature legislative achievement.

Obamacare will cost U.S. taxpayers $2.6 trillion over the next 10 years.