Example:

Assume the IRS issues a SNOD on June 1, 2020, for a Form 5330 return with a statute expiration date of July 31, 2020. The taxpayer has 90 days (until August 30, 2020) to petition Tax Court. The statute of limitations would be "extended" to December 28, 2020, (150 days are added to the original statute date) by the issuance of the 90-Day Letter. However, if the taxpayer signs Form 870-EP on June 21, 2020 (with 70 days remaining in the 90-day period), the statute of limitations would be shortened by 70 days to October 19, 2020.

Update the statute of limitations on AIMS and RCCMS after you mail the 90-Day Letter and when the taxpayer signs Form 870-EP or Form 4089.