There are a whole bunch of negative consequences to non-payment. First, the lender will try to withdraw the funds from your checking account. If they are unsuccessful, you will have to pay your bank NSF charges (Non-sufficient fund charges.) These usually range from $27 to $35.
There could be worse to come. You’ll probably start getting calls from collection agencies. Your credit score could be hit, as well. Finally, the payday lender may decide to sue you in civil court. Your property could be seized and sold off to pay the lender.