Question About Remedial Amendment Period

[Guest khartford]

When a remedial amendment period deadline is stated as the later of (1) the due date of the employer's tax return (including extensions) or (2) the plan year in which the provisions were first effective, what does "including extensions" mean? I have been interpreting this to mean that if your corporate tax return is due on March 15 then the due date of the employer's tax return including extensions is September 15 (including the automatic 6 month extension). Is that correct? Or do you actually have to apply for the extension? The requirement to apply makes little sense to me because the extension is automatic, and what difference does it make? Also, why would the IRS want to keep track of who filed for an extension and who didn't?

[K2retire]

If you do not apply for the automatic extension the due date is 3-15.