How do you know a corrective action actually worked?

In most systems a corrective action closes when the planned work is done. But that only says "we did what we said"; it does not say "it worked". Between the two there is a waiting period, and during it only one question means anything: did the same nonconformity come back? Effectiveness is measured after closure, not at closure — which is why the record needs an effectiveness field separate from the closure itself. Otherwise what you show the auditor is a commitment, not evidence. In SenSight QMS the corrective action record keeps effectiveness separate, so "done" and "worked" are not written in the same box.