This 23c date is the assessment date; the legal date that sets in motion the ten-year Collection Statute Expiration Date (CSED). This also starts the Collection Process. This notion of the assessment starting the CSED clock is important to teach you at this level as it sets the stage for later discussions. Congress did not intend to “judge” the nature of any assessment. Congress gives the IRS ten years to collect on any assessment. If Congress wanted to, it could change the law and make exceptions. When someone does not file a 1040 return and forces the IRS to create an assessment (a “Substitute for Return”-SFR) under IRC §6020(b), this assessment is not any different from the 1040-filed assessment you just created. There is a misconception in the tax pro world that an SFR has no CSED and this is not a fact. If you just think of the SFR as an assessment like any other, you recall “CSED is ten years from the date of assessment, plus any extensions to the CSED”.