(Image: J. David Ake, AP)

The website for the Internal Revenue Service is experiencing an outage on some of its electronic payment systems during the final hours of Tax Day.

Both the "Direct Pay" and "Payment Plan" options are listed as currently unavailable on the IRS website.

At one point, visitors to either of these payment options on the IRS website were greeted with a message that the system was down for a planned outage that would last from April 17, 2018 through December 31, 9999. The messages have since been updated to say the systems are currently unavailable.

As of 2 p.m. EDT on Monday, the "Pay by Debit or Credit Card" option -- which charges a fee for processing -- was the only working payment method.

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An IRS spokesperson confirmed the outages, noting that certain systems were experiencing technical difficulties, but that "taxpayers should continue filing their tax returns as they normally would."

It's still unclear what caused the crash or when the systems will be restored. UPDATE: IRS payment systems went back online Monday evening and taxpayers now have an automatic one-day file extension.

Coincidentally, IRS Acting Commissioner David Kautter was on Capitol Hill on Tuesday for a previously scheduled oversight hearing, where he told lawmakers that the outage was likely caused by technical problems on the department's internal systems. However, Kautter also said it was too early to rule out a cyberattack as the potential cause.