If everything is accurately verified, the IRS will issue your refund once they finish the review. It can take up to 45 days. But if you don't receive your refund or hear from them within 45 days, just give them a call at the phone number listed on the letter.
However, if you run into economic hardship and still haven't received your refund, you may be eligible for Taxpayer Advocate Service (TAS) assistance. You can reach them at 1-877-777-4778 and explain to them your situation. They will let you know if they can help speed the process along.