There are many reasons your tax return could be taking longer to process than you expected.  Some of the common errors are simple mistakes.  For example, your tax return could be slow to process because of incorrect social security number(s) for any of the joint taxpayers or dependents listed on your return, incorrect address, incorrect bank information (e.g., routing numbers, account numbers), if you use direct deposit.)
Incorrect Social Security or taxpayer identification number(s). This is true for joint taxpayers as well as dependents listed on your return; - Incorrect address; and - Incorrect bank information (e.g., routing numbers, account numbers), if you use direct deposit.