Americans who filed their 2019 federal income tax returns on time should expect a refund this week. 

The Internal Revenue Service and the Treasury Department will send interest payments with an average of $18 to about 13.9 million taxpayers, according to a statement by the IRS. 

The interest payments will be deposited to taxpayers who filed their tax return by this year's July 15 deadline and either received a refund in the past three months or will receive a refund.

Most interest payments will be issued separately from tax refunds, according to the statement. 

More than 12 million taxpayers who received their refund by direct deposit will see their interest payment direct deposited in the same account.

Those who didn't receive their payments through direct deposit will receive a check. A notation on the check − saying "INT Amount" − will identify it as a refund interest payment and indicate the interest amount.

These interest payments are taxable by law, and taxpayers who receive them must report the interest on the 2020 federal income tax return they file next year.

In January, the IRS will send Form 1099-INT to anyone who receives interest totaling at least $10.