It depends on what you claimed on your return. Most taxpayers who have not received their federal refund yet is due to the fact that they have claimed either or both the earned income tax credit (EITC) and the additional child tax credit (ACTC). 

The IRS issues most refunds in less than 21 days, although some require additional time. You should only call if it has been:

• 21 days or more since you e-filed
• 6 weeks or more since you mailed your return, or when
• "Where's My Refund" tells you to contact the IRS

According to the Protecting Americans from Tax Hikes (PATH) Act, the IRS cannot issue EITC and ACTC refunds before February 15. The IRS expects the earliest EITC/ACTC related refunds to be available in taxpayer bank accounts or debit cards on February 27, 2019, if these taxpayers chose direct deposit and there are no other issues with their tax return. 

Keep checking the status of your refund by click here: https://www.irs.gov/refunds