If you are paying annually, you would collect and remit the annual premium in advance. Hence, if the loan paid in full within the next year, a pro rata refund of the premium would be due to the mortgagor.
If you are collecting and paying the MI premium monthly, no refund would be due to the mortgagor upon payoff, since no premium had been paid in advance.
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Management is doing things right; leadership is doing the right things. Peter Drucker