Offer your thoughts or opinion on the input financial query or topic using your financial background.

Is it ok to use a check without a pre-printed check number?
For the clearing house, only the routing number and the check amount [which gets encoded before its presented to clearing] is important. The check numbers were put in as a fraud prevention mechanism to ensure that one check was only presented once and that it was issued to a particular account. Typically issued in sequence.   So as your account is new, the bank may have a mechanism to verify the checks [maybe based on amount and other info]. If your volume of check issuing increases, they may start putting in a check number to better track.