- 5 - Discussion We decide whether respondent timely issued the notice of deficiency to the Greenfields within the applicable period of limitations provided by section 6501(a). Respondent argues that the notice of deficiency was timely because the Greenfields’ execution of Form 872-A extended the period of limitations under section 6501(c)(4). Petitioners argue that the notice of deficiency was untimely. Alternatively, petitioners argue, the extension, if effective, applies only to the tax deficiency and not to the increased rate of interest. We conclude that the notice of deficiency was timely. We also conclude that the Form 872-A applies to both the income tax deficiency and the increased rate of interest. A. Burden of Proof As a general rule, Federal income tax must be assessed within 3 years after a tax return is filed. See sec. 6501(a). That period may be extended, however, by written agreement between the taxpayer and the Commissioner made before expiration of the general 3-year period. See sec. 6501(c)(4). The bar of limitations is an affirmative defense, and taxpayers raising it must specifically plead it and carry the burden of proof. See Rules 39, 142; Adler v. Commissioner, 85 T.C. 535, 540-541 (1985). A taxpayer can establish a prima facie case by showing that the Commissioner mailed the notice ofPage: Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 NextLast modified: March 27, 2008