After you file

After the IRS processes your return, if you're due a Federal refund, you should receive the refund.   The question would be "when?"

Is there more to the story?   For some reason you mentioned a letter.  Are you expecting a letter from the IRS?  If so, please explain.   Lots of returns are delayed for more processing and most don't get letters.  The IRS only sends a letter if they need something, such as more info, an identity verification issue, or dependent issue, or if they change something in your return, etc.

Otherwise, here's how to check on your refund:

If you efiled, double-check to be sure the return was efiled successfully and accepted.
If you used Online TurboTax, you can sign into your Online Account and check the efile status at the Tax Home.  If you used desktop software, you can check from within the software.

If that showed it was accepted, (or if you mailed a paper return), you can use the "Where's My Refund" tool at the IRS website below to monitor the status of your Federal refund.  

What is displayed there about your refund?  

Here are some tips when using the IRS "Where's My Refund" tool:

https://www.irs.gov/wheres-my-refund

• If you efiled, be sure you have waited at least 24 hours after acceptance before using the IRS WMR tool.   If you mailed a paper return, it won't show up in the tool for at least 4 weeks or longer.
• Be sure you enter the correct SSN and filing status.
• Be sure you are using only the Federal refund amount.   Do not include any state refund or any total refund or net refund (Fed and State) that TurboTax may have provided on a screen.  
• Look at your actual Federal return to get the Federal refund amount, i.e., your Form 1040, Line 35a.

• If the IRS WMR tool is not finding your information, you can also try phoning the IRS refund hotline.  I've seen it work for some users when the WMR tool didn't.  800-829-1954