Coverage End date (COVERAGE_END_DT) in Benefit Enrollment tables.
The Coverage End Date is a legacy field from a very early release of PeopleSoft that is no longer used. It is not populated by any online or batch process.
A new row inserted into the Health Benefit Enrollment with Coverage Elect of 'W' for Waive and 'T' for Terminated could indicated end of coverage and the Coverage Begin Date along with the Effective Date are used to identify the date coverage ended.
When you insert a new Coverage Begin Date, the prior coverage is assumed to be ended the day before.
For example,
Single Coverage, Effective 1/1/2009
Family Coverage, Effective 3/1/2009 (assumed single coverage ended on 2/28/09)