A setting that gives a shortcut for creating Else statements in eForm rules. When an eForm has a rule, and it loads at runtime, if the rule has a condition that returns false, the eForm logic rolls back or "undoes" the rule execution. This has the same effect as error handling in an Else statement. Thus, if you use auto undo, you do not need to create Else statements for rule conditions where the purpose of the Else statement is to abort the rule execution.
Note that some rule settings override the auto undo feature.