IRS Extending the Tax Assessment Period 

Length of Extension (Part II) 

In an open-ended consent, the extension period generally remains open until 90 days after either the taxpayer or the Service sends the prescribed notice ending the agreement. The procedures for using this consent are set forth in Revenue Procedure 79-22, 1979-1 C.B. 563, which may be obtained by calling the Internal Revenue Service at 1-800-829-1040 if the tax return being examined is one of the Form 1040 series of returns (for example, Form 1040, Form 1040A, Form 1040EZ) or 1-800-829-4933, if any other type of return is being examined. The open-ended consent may be used for cases placed in suspense, scheduled for appeals or other situations where it would be advantageous to both you and the Service to do so. 

Form 872-A, Special Consent to Extend the Time to Assess Tax, is used for agreeing to an open-ended assessment period. However, Form 872-A may not be used for employment taxes or certain miscellaneous excise taxes. 

IRS Publication 1035 (TTT 03/30/2021)