Good question to share @AJL,
Let me share my thoughts and discuss,
The target of verification is to ensure that your system is complying to the standard you established in place and no deviation happened.
So,the next step is defining who how and when do the verification?
For the first point, who will verify? The person who set the standard , the person in charge of the department or the team leader and you need to set a deputy in case the person in charge got his vacation.
How will you verify?
Actually,this point is up to you! Some industries considering internal audit is a type of verification,others can see that internal audit isn't enough so we have to verify more and more and take more samples on weekly basis, daily basis or monthly basis, it depends on the criticality of the topic you need to verify.
Finally, when to verify?
Based on the method of verification and result,you will set your frequency.