## Facts

- The IRS audited William D. Armstrong’s 1985 and 1986 federal income tax returns and later issued a notice of deficiency for those years.
- Armstrong used multiple addresses on different returns: P.O. Box 35343 (1985, 1986, 1989), 4150 S. 100th E. Ave., Ste. 308 (1987), and P.O. Box 74153 (1988).
- The 4150 S. 100th E. Ave. address was the business address of Armstrong’s former tax preparer, who told the IRS he no longer represented Armstrong and that Armstrong’s current address was P.O. Box 35343.
- Armstrong returned IRS forms (including a consent to extend the assessment period and a power of attorney) listing P.O. Box 35343 as his address and indicating he was formerly at the 4150 S. 100th E. Ave. address.
- The IRS later determined that P.O. Box 74153 did not exist.
- In December 1989, Armstrong’s former representative notified the IRS he no longer represented Armstrong and listed 417 W. 7th Street as Armstrong’s address; that address appeared in a separate IRS audit file for a different tax year.
- On March 2, 1990, the IRS mailed the 1985–1986 notice of deficiency by certified mail to P.O. Box 35343.
- The post office left certified-mail pickup notices in the box; the letter was returned to the IRS marked “unclaimed” on March 22, 1990.
- Armstrong filed a Tax Court petition on August 19, 1991 seeking redetermination of the deficiencies.
- The Tax Court dismissed for lack of jurisdiction as untimely, and Armstrong appealed.

## Issues

1. Whether the IRS mailed the notice of deficiency to Armstrong’s “last known address” under I.R.C. § 6212(b)(1).
2. Whether the IRS exercised reasonable care and diligence in selecting that address given conflicting address information.
3. Whether a deficiency notice returned “unclaimed” nonetheless starts the 90-day Tax Court petition period under I.R.C. § 6213(a).

## Decision

- The Tenth Circuit affirmed the Tax Court’s dismissal for lack of jurisdiction.
- The court held the IRS properly mailed the notice of deficiency to Armstrong’s last known address, P.O. Box 35343.
- Because the notice was validly mailed on March 2, 1990, the 90-day filing period began on that date, making Armstrong’s August 19, 1991 petition untimely.

## Legal Principles

- A notice of deficiency is valid if mailed to the taxpayer’s “last known address” under I.R.C. § 6212(b)(1), even if the taxpayer does not actually receive it.
- A taxpayer’s last known address is generally the address on the most recently filed and properly processed return unless the IRS has been given clear and concise notice of a different address.
- The IRS must exercise reasonable care and diligence in determining the taxpayer’s last known address but is not required to identify and use every address appearing in its files.
- When a valid notice is mailed, the 90-day period to petition the Tax Court under I.R.C. § 6213(a) is jurisdictional; a late petition requires dismissal.

## Conclusion

The court upheld dismissal because the IRS reasonably treated P.O. Box 35343 as Armstrong’s last known address and validly mailed the deficiency notice there; the notice being returned “unclaimed” did not prevent the statutory 90-day period from running, so the Tax Court lacked jurisdiction over the untimely petition.


Armstrong v. Comm'r, 15 F.3d 970 (10th Cir. 1994)