According to the IRS:
The IRS states that nine out of 10 e-filed tax returns with direct deposit will be processed within 21 days
of IRS e-file acceptance. If you opted to receive your tax refund via mail, it could take several weeks for your check to arrive.
Mailed paper returns: Refund processing time
is 6 to 8 weeks from the date the IRS receives your tax return.
