The IRS is reminding taxpayers they can start checking the status of their federal tax refund within 24 hours of filing their returns electronically by using either the IRS2GO mobile app or the IRS website’s online tool.

The Where’s My Refund? tool on the IRS website provides e-filers with the date the return was processed, when the refund was approved, and when the refund was deposited or mailed. The first update is provided in 24 hours for electronically filed returns and in four weeks for paper returns that are mailed to the IRS.

The IRS2Go app can be downloaded for free from Google Play, Apple’s App Store or Amazon.com. The links to all these sites are on the IRS website here.

Once a tax return is received, refunds are typically issued within 21 days unless the return requires additional review, the IRS says. Refunds can be delayed if a tax return contains errors, is missing information, is affected by identify theft, or claims the Earned Income Tax Credit or Additional Child Tax Credit.

The IRS said it contacts a taxpayer by mail if more information is needed to process or correct a return. The IRS reminds taxpayers that it does not send unsolicited emails, text messages, or use social media channels to contact taxpayers to request personal or financial information.

Taxpayers can find answers to questions, IRS forms and instructions, and easy-to-use tools online at IRS.gov anytime. The deadline to file federal income tax returns is May 17.