Nested IF statement with date comparison

I am either getting a #UNPARSEABLE error or #INCORRECT ARGUMENT with my formula. I am trying to compare two different date columns (Posted Date) or (Last Reviewed) against another date column (Deadline) to indicate a Yes or Review Needed. One of my columns (Last Reviewed) could be blank because it has been reviewed since posted. I need Yes if the Posted or Last Reviewed date is greater than the deadline, Review Needed if not or blank. I have tried a couple of versions.

=IF(Deadline19 > [Posted Date]19, "Review Needed", IF(Deadline19 > [Last Reviewed]19, "Review Needed"), IF(Deadline19 < [Posted Date]19, "Yes"), IF(Deadline19 < [Last Reviewed]19, "Yes"))

=IF(Deadline18 > [Posted Date]18, "Review Needed", "Yes", IF(Deadline18 > [Last Reviewed]18, "Review Needed", "Yes"))

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