Even though the IRS issues 9 out of 10 tax refunds within 21 days, it's possible your return may require additional review and take longer to process. IRS representatives will be able to research the status of your refund if your return was accepted (received) more than 21 calendar days ago. Call them at 1-800-829-1040, but prepare for potentially long wait times.
For some taxpayers, the identity-protection safeguards implemented by the IRS in recent years may account for longer wait times.
Other things that can delay your refund include but are not limited to:
Liens, back taxes, or refund offsets;
Errors, inconsistencies, or missing information;
Identity fraud;
Form 8397, Injured Spouse Allocation, which can take 11-14 weeks to process.
Please see below for more details.
https://ttlc.intuit.com/questions/1901548-why-do-some-refunds-take-longer-than-others
https://ttlc.intuit.com/questions/1894389-when-will-i-get-my-irs-tax-refund
https://ttlc.intuit.com/replies/3302084
