If you e-filed your tax return already, then unless it gets returned to you as "rejected" for some reason (such as having an incorrect Social Security Number, or a taxpayer name not being in the IRS database) you are unable to change your back account information on your tax return at this point in time.
The direct analogy is that of dropping a sealed envelope into a locked postal box; once something goes in, it cannot be recalled or come back out.
However, simply because your e-filed tax return doesn't have bank account information included doesn't mean that the IRS (and your state department of revenue, if applicable) won't process your tax return. Rather, it means that they will electronically process your e-filed return, and then physically mail you a traditional paper check to the home address you indicated at the beginning of your tax return.
This should only delay the receipt of your tax refund by a week or so; an e-filed return still has a much shorter processing time to it than a paper-filed tax return. The only inconvenience, if you view it as such, is having to deposit a paper check from the US Treasury at your local bank or other institution.
Thus, please don't worry about something that you cannot change. When the IRS encounters either missing or incorrect bank account information, they will automatically default to a mailing a paper refund check. On the other hand, if, instead of a tax refund, you owed money to the government, you can still send your payment to the IRS. Simply go to IRS.gov and download a blank Form 40-V payment voucher.
Thank you for asking this question, and please do not be concerned. Your situation is perfectly normal, and the IRS mails millions of paper refund checks every year.
