IRS Extending the Tax Assessment Period
Length of Extension (Part I)
The Service’s examiners will request an extension period no longer than is necessary to complete the examination and any administrative action necessary to process your case. As stated above, the Service uses two kinds of consents to accomplish this, a “fixed-date” and an “open-ended” consent.
Fixed-date consents expire on the date specified in the consent. Once the original date under the statute of limitations is extended by a signed consent, it may be further extended by the mutual agreement of the parties before the expiration date of the previous extension period. The fixed-date consent is used for most examination and appeal activities. The principal forms used are Form 872, Consent to Extend the Time to Assess Tax, Form 872-B, Consent to Extend the Time to Assess Miscellaneous Excise Taxes, or Form SS-10, Consent to Extend the Time to Assess Employment Taxes.
IRS Publication 1035 (TTT 03/23/2021)