Tax season is officially underway and the Internal Revenue Service expects more than 140 million returns to be filed ahead of the filing deadline on April 15.

READ MORE: IRS accepting tax returns now: When can I file a return? Where’s my refund? Can I file for free?

The IRS began processing tax returns Monday. For filers who submit their returns electronically using direct deposit, refunds are generally issued in less than 21 days. There is a caution from the tax agency, however, that urges “taxpayers not to rely on receiving refund by a certain date, especially when making major purchases or paying bills.

“Some returns may require additional review and may take longer,” the IRS added.

Some credits also prompt longer waits for refunds. Under the federal Protecting Americans from Tax Hikes, or PATH, Act, the IRS cannot issue Earned Income Tax Credit or Additional Child Tax Credit refunds before mid-February due to extra identity checks with those credits. The IRS expects EITC/ACTC-related refunds to be available in bank accounts or on debit cards by March 3, assuming there are no other issues with their tax return.

READ MORE: Claimed Child Tax Credit when filing taxes? Here’s the soonest you can expect your refund

You can use the IRS “Where’s My Refund” tool to track your refund. To check, you will need your Social Security number or individual taxpayer ID number, your filing status and exact refund amount on your return.

The information on “Where’s My Refund?” is updated once a day, overnight so there’s no need to check more than once a day.