The observation history feature allows you to see when an observation was changed, for what reason and by whom.

It creates an audit trail of changes which is often required for registration trails that need to follow GLP (Good Laboratory Practices) guidelines or any situation where changes in observations need to be noted and visible.  

When this add-on is enabled, users are prompted to enter a “Change Reason” whenever an observation is altered.  This provides additional information about why a record was changed.

The audit log add-on helps establish a chain-of-custody that allows organisations to see exactly what observations were changed, when, by whom and why, so trials have a complete history of observation records.