In most cases, you will hear back from the IRS within 24 hours of submitting your business tax extension online. However, it’s important to note that IRS response times will be longer than normal on the last day of filing (March 15 and April 15). As soon as your business extension is approved by the IRS, you will receive an email from TaxExtension.com with the details of your extension, including your official IRS confirmation number.