If you answered all of the questions accurately and you qualified, Turbo Tax would have included the Earned Income Credit to your refund. Perhaps something was missing in the return.
I have never heard of the IRS giving a refund out and then a few weeks later requesting information to give an additional refund. Make sure you mailed it to an IRS mailing address and that you did not include information they did not already show you in the letter. Meaning, if there was no social security number in the letter, do not give it to them.
