When you receive any kind of letter from the IRS and/or yous state it can be scary. If you received letter 4464c it means that the IRS has pulled your tax return for a review, but it is not considered an audit. The IRS is working to verify the information reported on your tax return and matching documents they received from payers such as employers, banks, etc.
If the IRS needs any more from you they will send you another letter with an explanation and how you can get them the information.