Subsection (a) shall not apply to any sale or exchange by the taxpayer if, during the 2-year period ending on the date of such sale or exchange, there was any other sale or exchange by the taxpayer to which subsection (a) applied.

Link: https://www.law.cornell.edu/uscode/text/26/121.

Bob you may be correct, but my understanding was only one exclusion every two years, so how can client take two exclusions in one year ?