By now, you've heard all about the Northern California couple who discovered about $10 million in buried treasure while they were out walking their dog. But before you get too jealous of those guys, you should know that the IRS wants their share of the find this April, and the bill isn't pretty.

As LAist reports, a couple, who media are pseudonymously referring to as "John and Mary" (they don't want their names out there for privacy reasons), were walking their dog on their Sierra Nevada property when they found eight metal cans filled with what turned out to be 1,427 mint-condition gold coins dating from 1847 to 1894.

According to numismatists, the rare coins (which have been dubbed the Saddle Ridge Treasure) could be sold for around $10 million. As the Chron reports today, though, the couple will owe nearly half that in taxes, whether they sell the coins or not.

1969's Cesarini v. United States court case determined that found treasure is considered taxable income the year it's discovered. That decision set the IRS up to say in their tax guide that "If you find and keep property that does not belong to you that has been lost or abandoned (treasure-trove), it is taxable to you at its fair market value in the first year it is your undisputed possession."

Add up the federal tax rate of 39.6 percent and the California rate of 13.3 percent, and you'll see that "John and Mary" probably need to come up with about 47% of the coins' estimated value for the taxmen by April 15. Otherwise, they'll face significant interest and penalties, reports the Chron.

Tiburon coin dealer Don Kagin will be selling the Saddle Ridge Treasure for the couple, placing 90 percent on Amazon's "Collectibles" section, and selling others directly to collectors.

The couple also plans on keeping a few coins for themselves. Kagin tells the Associated Press they'll will use the money generated by the coin sales to pay off bills and to donate to area charities.