### Question
How is the term 30-day letter defined?


### Answer
The term **30-day letter** is defined in *26 U.S.C. § 6603* as the following:

> the first letter of proposed deficiency which allows the taxpayer an opportunity for administrative review in the Internal Revenue Service Independent Office of Appeals

#### Citation:
  - *26 U.S.C. § 6603*
  - Heading: **Subtitle F-Procedure and Administration > CHAPTER 67-INTEREST > Subchapter A-Interest on Underpayments**

