If a debit card purchase or check is returned unpaid,how many times can the merchant submit it again for pymnt?

a pin purchase will usually not get approved if the money is not available, that's why peoples cards get declined at the POS (point of sale). sometimes it will not get approved when you try to do it as credit either if you dont have the money. i have never heard of a card purchase being returned after the fact, it will just get paid, the bank will charge you an overdraft fee and your account will be negative.

a check on the other hand... I am not sure if there is a limit on submissions. most of the time the merchant will just charge you a fee and send you a bill after the first time unless it is something important like a mortgage payment. call the merchant.

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Just put the money in the bank....