ANDREW TAYLOR, Associated Press

WASHINGTON (AP) — The Treasury Department has a message for taxpayers getting calls from the IRS demanding immediate payment: Hang up.

Those aggressive, threatening calls are coming from phone scammers. And they’re successful, too, costing more than 5,000 victims upward of $26.5 million since October 2013. About 900,000 scammer contacts were reported during that period.

Officials say the callers fraudulently claim to be with the IRS and demand that taxpayers immediately send them payment. They often have some personal information about the person they’re calling and threaten criminal charges unless immediate payment is made.

Meanwhile, tax filing season opened Tuesday, and the IRS says its systems are running smoothly.